Environmental Geology

Lecture Notes

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Earth: The Only Special Planet                                  Back to top

Origin of the Solar System

• The Solar System -
• Sun, 9 (1) planets, asteroids, moons, comets
• Formed from the solar nebula
• Sun and planets (including Earth) formed about 4.6 billion years ago
• Composition of each planet determined largely by distance from Sun

Solar System

• Terrestrial Planets
• Mercury, Venus, Earth, Mars
• Close to the Sun
• Small
• Rocky
• Densities > 3 gm/cm3

Other Objects in the Solar System

• Asteroids
• Many small bodies orbiting between Mars and Jupiter (Asteroid Belt)
• Kept from forming a planet by massive gravitational pull of Jupiter
• Some have orbits that cross that of Earth
• Comets
• Icy bodies with very eccentric orbits

Earth’s Place in the Universe

• One of nine planets in our Solar System
• Formed at the same time as other planets (approximately 4.6 billion years old)
• One of the inner, or terrestrial, planets
• Contains H₂O as solid, vapor, and liquid
• Only planet known to support life

Earth as a Planet

• Early Earth
• Formed at same time as other planets
• Gravitational attraction of particles caused them to coalesce
• Impact energy of larger and larger bodies produced heat
• Compression in interior as planet grew caused temperature to rise
• Radioactive elements also added heat
• Heat powered early geologic processes
• Melted planet
• Caused denser material to sink, lighter material to float
• Resulted in layered planet:
  • Iron-rich core
  • Rocky, but dense, mantle
  • Rocky, but less dense, crust
• Early Earth too hot for atmosphere or ocean
• Melting of interior released volatiles
• Most H₂O condensed to form oceans
• Gaseous elements formed atmosphere
• Some people believe much (most) of material in oceans and atmosphere came from "outer space" in form of comets
• Early atmosphere different from today
• Little oxygen present
• Mostly nitrogen and CO₂, with minor methane, ammonia, sulfur gases
• Early life forms derived energy from these substances
• Oxygen produced as poisonous by-product of metabolism of early life forms
• Earth has changed dramatically since its formation
• Core is crystallizing, releasing heat
• Mantle convects as result of heat
• Mantle has melted, producing more crust
• Convection causes movement of surface "plates" responsible for most modern geologic phenomena
• Continual change is normal consequence of geologic processes
• Cyclical changes
• Linear changes (irreversible)
• How much change is natural, and how much is result of modern human activity
• Have to be able to read Earth’s history to answer this question

Understanding Earth

• The Scientific Method
• Means of discovering basic scientific principles
• Begins with set of observations
  • Body of data based on measurements of natural phenomena
• Formulate hypothesis
  • Must be stated in such a way as to be testable
  • Devise and conduct experiments to test hypothesis
• If experiment contradicts hypothesis, then hypothesis must be modified or abandoned
• If experiment is consistent with hypothesis, credibility is gained
• New experiments devised and conducted
• Any hypothesis that withstands multiple tests gains status of theory
• Problems with testing hypotheses about Earth’s behavior:
• Large spatial scale
• Long time frame
• Often difficult to reproduce natural conditions in laboratory or that can be conducted within human lifetime
• The Science of Geology
• Observe modern processes
• Formulate hypotheses consistent with what is currently observed
• Must be compatible with known physical laws
  • Gravity
  • Thermodynamics
  • Physics and Chemistry
• Search ancient geologic deposits for clues to:
• Past live forms (fossils)
• Past climates (e.g., Ice Ages)
• Past rates of geologic processes
  • Erosion and deposition
  • Volcanic activity
  • Mountain building (earthquakes)
• Combine information from many different places and rocks of different ages
• Compile this information into logical order
• Result is known as the Geologic Column
• Divide major periods in Earth’s history into the Geologic Time Scale
• How this is done is topic of next lecture

Geologic Time

Relative Time

 Relationships of events to each other

Which event is older, which younger

What clues are in the geologic record

What principles can be applied

 Principle of Uniformity

Uniformitarianism

Concept that the same basic physical laws have operated throughout Earths history

Present is the key to the past

Can infer much about processes operating in the past by studying present geologic processes and their products

Does NOT mean rates are the same

Relative Time

Principle of Superposition

In an undisturbed pile of sedimentary rocks, those on the bottom were deposited first; those on top, last

Implies that rocks did not all form at the same time

Does not tell us how long it took for the sediment to form, or if there are gaps in the record

Relative Time

Principle of Original Horizontality

Sediments are deposited in approximately horizontal, flat-lying layers

Sedimentary rocks found that are not horizontal are presumed to have been deformed (tilted) subsequent to their deposition

Deformation is thus a later event than deposition

The Principle of Cross-cutting Relationships

If an igneous rock cuts across layers of another rock, the intruded rock must have existed before the magma was emplaced

Therefore, the igneous rock is younger than the intruded rock

The Principle of Inclusion

If an igneous rock contains pieces of other rock types, those pieces must have already existed when magma intruded

Therefore, magma is younger than included pieces

Correlation of Separated Units

Law of Faunal Succession

Life forms change through time

Old forms disappear, new forms emerge

Same form never duplicated twice

Can use presence of fossils (remnants of past live forms) to correlate widely separated rocks

Better than using rock type, which may change with distance

Geologic Time Scale

Based on rocks correlated over entire Earth using fossils

All of geologic time can be divided into a few large subdivisions

Precambrian

First 4 b.y. (~86%) of Earth History

Only a few fossils are found

Simple life forms; few hard parts

Phanerozoic (Visible Life)

Abundant fossils

Divided into Eras

Paleozoic Era - Ancient Life

Life in sea gradually moves onto land

Mesozoic - Middle or Intermediate Life

Age of the dinosaurs

Cenozoic - Modern or Recent Life

Age of mammals

Divisions of Earth History

Boundaries between different geologic time units based on dramatic change in life forms

Mass extinctions followed by rapid radiation of new life forms

Causes of mass extinction subject to debate, but clearly from natural causes  (Asteroid impact Volcanic activity)

Mass Extinctions

Humans first appeared near end of Cenozoic

Came out of Africa and expanded over all the Earth

Human population growth causing one of the greatest mass extinctions of other animals and plants in Earths history

Absolute Time

Geologic Principles only tell relative age relationships

How do we determine the actual time of formation of different rocks

Utilize radioactive decay of some elements

Absolute Time

Radioactivity

Spontaneous decay or breakup of unstable atoms characterized by a constant rate of decay

Time required for one-half of the amount of a material to decay is the half-life

Half-lives vary from seconds to billions of years

Radioactive Dating

Selection of isotopic system

Parent isotope must be abundant enough to measure

Must be able to determine how much of daughter isotope was produced by decay

Half-life must appropriate to age of event being dated

Useful radioactive elements:

U, Th, K, Rb, and C

Combination of Radiometric and Relative Ages

Not all rocks amenable to radiometric dating

Can still use basic geologic principles to determine relative ages

Assign absolute ages where possible; interpolate between these dates

World Population Growth

Carrying Capacity

• The ability of a system (or the whole Earth) to sustain its population in reasonably healthy and comfortable conditions
  • Resource consumption
    • What is a resource
    • Consumption related, in part, to population

World Population Increase

• 1960: 2%/year (doubling time = 36 years)
• 1980: 1.7%/year (doubling time = 41 years)
• 2000: 1%/year (doubling time = 72 years)
• 1994: World population about 5.66 billion people. Increasing by 94 million/year (10,000 new people per hour)
• Uneven population growth: Africa, Asia, and Latin America (4 billion people) have highest growth rates
• Factors important to growth rate:
  • Birthrate
  • Death rate
  • Age Distribution (% of people in each of three categories)
    • Pre-reproductive age (<14 years old)
    • Reproductive age (14-49 years old)
    • Post-reproductive age (50 years old)

Expansive Populations

• Large pre-reproductive percentage yields expansive growth
  • Growth rate will increase in future, all else constant
  • Mexico:
    • 2.2% population increase (27 year doubling time).
    • 42% of population <15 years old
    • Average of undeveloped world is 40% < 15 years old

Stationary and Constrictive Populations

• Equal proportions of all 3 age groups yields stationary population
  • Example is Sweden
• Small pre-reproductive percentage yields constrictive population
  • Growth rate will decrease in future, all else constant

Demographic Transitions

• Demography: Science of population growth
• Less developed countries have highest population & growth rates
• Most technologically developed countries have lowest growth rates

Demographic Transition Models: Succession of Stages

• Stage I - High birthrate & high death rate
  • very low population increase
• Stage II - High birthrate & low death rate
  • rapid growth rate
• Stage III - Decreasing birthrate
  • declining growth rate
  • Mexico: 1970 - 3.5%/year; 1988 - 2.6%/year
• Stage IV - balanced birthrate and death rate

Demographic Transition Model

• Problems with model
  • Time
    • Developed world in past - Europe, N. America, etc.
    • Underdeveloped world today - Africa, etc.
    • Rapid drop in death rate but still high birthrate

Resource depletion in future

WORLD POPULATION GROWTH

POPULATION GROWTH, URBAN/RURAL

Demographic Trap

• Underdeveloped world
  • 2nd stage of the model: high birthrate/low death rate
    • 3%/year growth
    • carrying capacity extended
    • deforestation and farming practices
    • groundwater depletion
    • effects are less food, lower income - cycle

INCOME CHANGES, 1980-1986

• Rising Incomes
  • China +58%
  • S. Korea +34%
  • Japan +21%
  • India +14%
  • W. Ger. +10%
  • UK +12%
  • USA +10%
  • France + 3%
• Declining Incomes
  • Nigeria -28%
  • Argentina -21%
  • Philippines -16%
  • Peru -11%
  • Kenya - 8%
  • Mexico - 7%
  • Sudan - 7%
  • Brazil - 6%

EST. POP. AT STABILIZATION
(From Worldwatch, 1987)

Country Current Pop. (million) Est. Stable Pop.

China 1,050 1,571 (+50%)

USA 241 289 (+20%)

West Germany 61 52 (-15%)

Nigeria 105 532 (+406%)

Pakistan 102 330 (+223%)

Iran 47 166 (+253)

Mexico 82 199 (+143%)

India 785 1,700 (+116%)

Year 2025: 8.5 billion! = 50% increase over 1994

Comparative Impacts on Earth

• Impacts on Earth - the effects on Earths ecosystem by people in different countries
  • Formula I=PAT
    • I is impact of a countrys people on Earths ecosystem
    • P is countrys total population
    • A is affluence of those people
    • T average technological level of that country

Comparative Impacts on Earth

• Estimation of I
  • Assume AxT = per-capita use of commercial energy (which is published)
  • Using this formula, a person in the USA has 3 times the impact on the Earth as one in Sweden, and 181,000 times that of a person in Nigeria

Implications of Population Growth

• Shortages
  • Food supplies. Renewable, "elastic", within limits
  • Mineral resources. Not generally renewable
  • Land

Implications of Population Growth

• Changes in global environment
  • Deforestation
    • Amazon River Basin: 1987 - 8 million hectares (19 million acres, or 3 million sq. miles) deforested
  • Desertification
    • overgrazing
    • salinization by irrigation
    • overcultivation (soil depletion)
• Pollution
  • Sources
  • Types
    • Water pollution
    • Persistent substances - DDT, mercury, lead
    • Non-persistent problems - many organic substances
    • Air pollution
    • carbon monoxide, hydrocarbons, particulates, sulfur dioxide, nitrogen compounds
• Global Warming and Ozone Depletion
  • Global warming - climate change
    • causes
      • carbon dioxide
      • other gases - methane and nitrous oxides
    • effects
      • temperature of atmosphere (Greenhouse Effect)
      • climate pattern changes
      • flooding of coastlines due to glacier melting
  • Ozone (O₃) destruction
    • Production in upper atmosphere - ozone layer

O₂ +E_UV(sun) -- 2 O; O + O₂ -- O₃

o        Destruction - fluorocarbons

o        Effects

§         skin cancer rates

§         life on Earth

Earth Materials                                            Back to top

All matter made from elements

Simplest form of any element is the atom

Atoms smallest unit that possesses physical and chemical traits of the element

Atoms have nucleus containing fixed number of protons (+) and variable number of neutrons (neutral)

Electrons (-) orbit the nucleus

Neutral atom has equal protons and electrons

Atoms, Isotopes and Ions

Number of protons in nucleus same for all atoms of a given element

E.g., all carbon atoms have 6 protons

Number of neutrons may vary between different individual atoms of same element

E.g., carbon may have 6, 7, or 8 neutrons Atoms of different atomic mass called isotopes

Some isotopes stable, others radioactive

Electrons encircle nucleus in different orbits

Configuration of orbits in some atoms more stable than others

Atoms strive to achieve stable orbit configuration by exchanging or sharing electrons with other atoms

Compounds

Atoms that share electrons combine by covalent bonding

Ions that exchange electrons form ions; combine by ionic bonding

When elements combine with each other, they form compounds

Minerals represent one category of compounds

 Minerals

Definition

Naturally occurring

Inorganic

Possess definite chemical composition (within limits)

Crystalline

Solid in which atoms are arranged in a regular, 3D repeating pattern

Common Minerals

About 3000 minerals identified (2 from Moon)

Most not common

12 Elements make up over 99% of crust by mass

2 Elements make up over 70% of crust by mass (Si & O)

Oxygen makes up 94% of crust by volume

Most common minerals in crust contain silicon and oxygen

Si & O combine to form the silica tetrahedron (1 Si surrounded by 4 O)

This combination does not satisfy all the electronic charges

Result is (SiO₄) ^{4 -}

Silicates

Minerals based on silica tetrahedron called silicates

Other, less abundant, elements incorporated into minerals to satisfy charge

Two most common minerals in crust are quartz and feldspar

Other silicate minerals include mica, pyroxene, amphibole, garnet, olivine

Other Mineral Groups

Native elements (carbon, gold, silver)

Other elements form different anionic units

Oxides: contain O^2-

hematite (iron ore), corundum (important abrasive)

Sulfides: contain S^2-

pyrite (fools gold), galena (ore of lead)

Halides: contain halogen ion (F^-, Cl^-, Br^-, I^-)

halite (table salt), fluorite (used in steel making)

Sulfates: contain (SO₄)^2-

gypsum (wall board)

Phosphates: contain (PO₄)^3-

apatite (teeth, bones,)

Carbonates: contain (CO₃)^2-

calcite, dolomite

important rock-forming minerals -> limestone

common material in shells of invertebrates

used for cement, ag lime, aggregate in concrete

Rocks

Textbook definition:

Solid, cohesive aggregate of one or more minerals, or mineral materials

Some rocks contain other material as well

Coal contains hydrocarbons - organic material, hence not minerals

Most rocks contain many individual grains of minerals held firmly together

Rock Types

Three major types of rocks

Igneous rocks - formed by cooling of magma (molten rock)

Sedimentary rocks - formed at Earths surface by deposition of sediment

Metamorphic rocks - formed inside Earth at high temperatures and pressures, but not high enough to melt the rock

Rock Cycle

Rocks are not necessarily permanent features

One rock type may be converted to a different rock type by normal geologic processes

The constant reworking of rocks is called the Rock Cycle

Igneous Rocks

Form from magma (melted rock)

Requires very high temperatures

Melting occurs at great depth in Earth

Magma commonly moves from site of origin to cool elsewhere

Rate of cooling affects size of minerals

Magma that cools slowly underground forms large crystals

These rocks are called plutonic (after Pluto, Greek god of the underworld)

Form coarse, interlocking texture of mineral grains

Most common example is granite

Some magma will actually reach surface before it cools

Forms extrusive bodies (volcanoes)

Extrusive rocks cool much faster than intrusive (plutonic) rocks

Crystals are smaller; may not form at all (obsidian = volcanic glass)

Some magma cools for a time at depth, then moves upward and cools at faster rate than originally

Produces different sizes of crystals

Texture is called porphyritic; indicates two periods of cooling

Another clue to Earths history

Sedimentary Rocks

Form from sediments

Loose, unconsolidated accumulations of mineral particles that have been transported by water, wind, or ice or shifted under the influence of gravity

Most sediment originates by weathering of pre-existing rocks

Physical breakup into finer and finer fragments

Solution of soluble minerals

Sediments deposited under influence of gravity

Deposits form in horizontal or nearly horizontal layers called strata (singular = stratum)

Cover Earth as a thin reaction veneer on the continents between solid earth and atmosphere

Pre-existing particles called clasts

Rocks made from pre-existing particles -> clastic sedimentary rocks

Rocks made from precipitation of dissolved material -> chemical sedimentary rocks

Both types require compaction and cementation of the sediment - called lithification

Clastic Sedimentary Rocks

Form from finer particles of pre-existing rocks

Categorized by size and shape of the particles

Most common types are

sandstone (sand-sized particles)

shale (silt and clay-sized particles)

conglomerate (pebble-sized particles)

Chemical Sedimentary Rocks

Form by precipitation of dissolved material

Common types:

limestone: calcium carbonate (calcite)

often result of invertebrates and some plants making shells or stems

gypsum: calcium sulfate

rock salt: sodium chloride

gypsum and rock salt form from evaporation of seawater in restricted basin

Chemical sedimentary rocks are, themselves, soluble

May be highly porous because of solution

Commonly form caves and caverns

May also be dissolved by groundwater and act as source of contamination

hard water

formation of unpotable brines

Metamorphic Rocks

Formed by changes to preexisting rocks under high temperature and pressure conditions

Changes occur in the solid state, i.e., rock does not melt

Changes may result in different texture and/or growth of new minerals

Metamorphism occurs most commonly at

plate boundaries (especially subduction zones)

surrounding intrusion of magma into cold country rock

Metamorphism of a large area called regional metamorphism

Metamorphism surrounding intrusion of magma called contact metamorphism

Heat and pressure cause change in texture of mineral in rock

Recrystallization of preexisting grains may without formation of new minerals

quartzite - metamorphosed sandstone

marble - metamorphosed limestone

Heat and pressure commonly cause chemical reactions, producing new minerals

New minerals are commonly aligned because of pressure differences

Produces a phenomenon called foliation

Slate, schist - form platy sheets of micas

Gneiss - bands of light and dark minerals

Most of continental crust is metamorphic

Only exposed in limited places (e.g., cores of mountain ranges)

Of limited economic importance, but very important in study of Earths ancient history - retain record of events that caused the metamorphism

The Rock Cycle Revisited

Rock cycle shown earlier too simplistic

Rocks of any type can be transformed into rocks of another type of into another distinct rock of the same general type

There are many short circuits within the Rock Cycle

Interpreting Earths history requires trying to decipher them all

END

Plate Tectonics                            Back to top

Continental Drift

• Outlines of some continents fit together like pieces of jigsaw puzzle
• Hypothesized that they were once connected
• Alfred Wegener championed concept of continental drift
• Not generally accepted because no known mechanism for continents to move

Behavior of Materials

• Materials inside Earth are subjected to stresses
• Stresses divided into three categories
  • Compressive stress - forces directed toward a central point (compression)
  • Tensile stress - forces directed away from a central point (tension)
  • Shear stress - forces directed opposite each other so as to create a shear couple
• Materials subjected to stresses deform
• Deformation is called strain
• Type and amount of strain varies with:
  • nature of material
  • type and amount of stress
  • temperature and pressure
  • time

Types of Strain

• Elastic deformation
  • Strain is proportional to stress
  • Strain is reversible
  • Materials have an elastic limit
• Plastic deformation
  • Strain not proportional to stress
  • Small increase in stress yields large change in strain
  • Not reversible
• Brittle deformation
  • Materials break (rupture) when excess stress is applied
  • Typical of material under near-surface conditions

Lithosphere and Asthenosphere

• Rocks in outermost portion of Earth are at relatively low temperatures and pressures
• Behave in a brittle manner when elastic limit is exceeded
• Region of Earth called the lithosphere
• Varies in thickness from approximately 50 to 100 km
• Includes crust and uppermost mantle
• Rocks below the lithosphere are under elevated temperature and pressure
• A layer exists in which rocks behave in a plastic manner
• This layer is called the asthenosphere
• Exists to average depth of approx. 300 km
• Higher pressure at depths greater than 300 km increase rock strength

Evidence Accumulates

• Discovery of asthenosphere provided mechanism by which continents could move
• Did not prove this occurred, however
• Additional evidence needed before most geologists would accept the idea that Earths solid surface could move around

Distribution of Earthquakes

• Earthquakes do not occur in random locations
• Compilation of seismic (earthquake) data show definite concentrations along narrow zones
• Define edges of large "tectonic plates"

Seafloor Topography

• Bathymetric (deep ocean) soundings revealed presence of long elevated ridges in deep ocean basins
• Location of these ridges correspond to regions of high seismic activity
• Also correspond to regions of high heat flow and abundant volcanic activity

Magnetism

• Some minerals (esp. iron oxides) are magnetic at temperatures below their Curie point
• Alignment of magnetic particles influenced by Earths magnetic field
• Magnetic field known to reverse itself at irregular intervals throughout Earths history

Magnetic Stripes on Seafloor

• Magnetic surveys made of deep ocean basin during Cold War
• Odd pattern of magnetic stripes discovered
• Finally explained as resulting from spreading of ocean basin at mid-ocean ridges
• Magnetic minerals act as "tape recorder" as magnetic field reverses its polarity

Age Distribution of Sea Floor

• Global-wide surveys of magnetic stripes allowed geologists to correlate stripes of same age
• Drilling programs in deep ocean basins recovered thousands of samples of ocean floor basalt
• Radiometric age determinations show symmetrical pattern away from MOR

Polar Wander Curves

• Continents preserve much older rocks than ocean basins
• Magnetic minerals in continental rocks of different ages point toward different magnetic North Poles
• Also indicate different latitudes at time of formation
• Has magnetic pole moved significantly during Earths history
• Magnetic pole caused by rotation of planet on its axis, sloshing liquid iron core as it spins
• Magnetic poles should remain near geographic poles
• If location of magnetic poles has remained essentially the same, why do rocks point to different locations
• Why do different continents indicate different polar wanderings
• Can explain if continents move relative to stationary magnetic poles

Other Evidence

• Evidence of past glaciation in areas now at low latitudes
• Distribution of the same plant and animal fossils from widely separated areas
• Same sequences of rocks on opposite continents
• Can be explained if continents were once connected

Reconstruction of Continental Assemblages

• Combining multiple lines of evidence allows geologists to reconstruct past positions of continents
• All continents connected in a super continent (Pangea) 200 million years ago
• Separated into two large regions (Laurasia and Gondwanaland) by 100 million years ago
• Detailed studies of older rocks indicate that continents have come together at other times in Earths history, then broken apart again
• Known as the Wilson Cycle

Requires approximately 400 million years for each Wilson Cycle to be completed

Seafloor Spreading

• Abundant evidence found that continents have not always been in their current locations
• Rocks near Earths surface too brittle for continents to move through them
• How to reconcile
• Explained by theory of seafloor spreading
• Major piece of evidence was magnetic stripes parallel to mid-ocean ridges
• Also, lack of rocks in ocean basin older than about 180 million years old
• Theory proposed that lithosphere is top of convection cells that form as heat escapes from Earths interior
• Upwelling convection currents cause brittle lithosphere to fracture and spread apart
• New material injected at fracture in the form of basaltic lava
• Cooling lava records magnetic reversals
• Continents are passengers embedded in these lithospheric "plates"

Subduction Zones

• Earth is not expanding, so material from mantle injected at mid-ocean spreading centers must be replaced
• As ocean floor cools, it become denser
• Dense rock sinks and returns to mantle
• Regions where this return flow occurs are called subduction zones (Benioff Zones)
• Subduction zones may occur where old ocean floor sinks under another part of the ocean basin or under the edge of a continent
• One forms island arcs (Japanese Islands, Aleutian Islands, Philippine Islands)
• One forms continental arcs (Andes)

Collision Zones

• Continental crust less dense than oceanic crust
• Cannot return to mantle because too buoyant
• When two continents come together, they collide
• Collision creates doubly thick crust (Himalayas)

Transform Faults

• Lithospheric plates move around surface of the globe
• Cannot connect margins of plates on a sphere with just divergent (spreading) and convergent (subduction) zones
• Must have zones where plates move past each other (shear)
• Called transform faults
• Transform faults connect different kinds of plate boundaries together (i.e., transform one boundary to another)
• Provide clinching evidence for plate tectonic theory
• Cannot exist in the absence of plate tectonics
• Most famous transform fault is San Andreas Fault in California

Hot Spots

• Evidence exists that some regions in the mantle produce copious amounts of magma
• Called "hot spots"
• Appear to be stationary; do not move with convection cells
• Instead, lithospheric plates move over them
• Form linear chains of volcanic islands and/or seamounts (Hawaiian Islands)

The Rock Cycle Revisited

• Igneous rocks form at mid-ocean spreading centers and subduction zones
• Tectonic processes uplift rocks and expose them to weathering and erosion, forming sediment

Rock and sediment are subducted and metamorphosed under elevated temperatures and pressures

Earthquakes                            Back to top

• What causes earthquakes
• How are earthquakes measured
• Are some areas more prone to earthquakes than others
• What hazards are associated with earthquakes
• Can earthquakes be predicted

What Causes Earthquakes

• Sudden release of accumulated elastic strain when rock under stress ruptures
• Point of rupture is called the hypocenter or focus
• Point on map directly above hypocenter is called epicenter
• Elastic energy is released as seismic waves

Seismic Waves

• Seismic waves occur as body waves and surface waves
• Body waves travel through the Earth
• Primary waves
• Shear waves
• Surface waves travel along surface
• Love waves
• Rayleigh waves

Body Waves

• Primary, or P-waves, travel in push-pull fashion (compression - extension)
• Travel through solid or liquid
• Velocity dependent on bulk modulus, rigidity, and density of medium through which it travels
• Shear, or S-waves, move in an up-and-down or side-to-side manner that is transverse to propagation direction
• Travel through solids only
• Velocity is approximately 2/3 that of a P-wave travelling through the same medium

Surface Waves

• Love Waves
• Form when S-waves reach surface
• Cause horizontal motion only
• Rayleigh Waves
• Produce circular motion (like ocean waves)
• Exhibit considerable vertical motion

Detecting and Measuring Earthquakes

Detecting Earthquakes

• Seismic waves are measured using a seismograph
• Because P- and S-waves travel at different rates, can determine distance to the epicenter from a recording station by measuring difference in arrival times

Measuring Earthquakes

• Size of an earthquake can be stated in qualitative or quantitative terms
• Intensity is a qualitative expression of the amount of damage caused by an earthquake
• Intensity decreases with distance from epicenter
• Levels of intensity given by Modified Mercalli Scale

• Magnitude is a quantitative measure of the amplitude of the largest seismic wave produced by an earthquake
• Values of magnitude based on the Richter Scale
• Richter Scale is logarithmic with no theoretical upper limit
• Great EQs have M equal or greater than 8

Are Some Areas More Prone to Earthquakes than Others

• Most earthquakes occur at plate boundaries
• Great EQs especially associated with subduction zones
• Some transform boundaries produce great EQs because of "locking" of fault
• Some great EQs associated with weak areas within plates

Earthquake Hazards

• Aseismic creep moves blocks of crust slowly, realigning them
• Landslides
• Tsunamis: giant ocean waves caused by submarine earthquakes
• Coastal Flooding
• Liquefaction of saturated soils
• Fire

Earthquake Prediction

• "Only fools, charlatans, and liars claim to be able to predict earthquakes"
• All earthquakes start the same; difference between small and large EQs is where they stop
• Some EQs have been predicted successfully, but others have been missed
• China predicted several large earthquakes in 1975-1979 and saved untold number of lives
• Magnitude 8 EQ struck later, killing 250,000

Earthquake Prediction

Earthquake Control

• Can seismic stress be released in small increments rather than allowing it to build up to catastrophic levels
• Edward Teller (Father of the H-Bomb) advocated small nuclear explosions along San Andreas Fault
• Fluid injection wells at Rocky Mountain Arsenal caused increase in small earthquake activity
• Not seriously considered at present: too many unknown variables

Volcanoes                                 Back to top

Points to Consider

• How do volcanoes form
• Where do volcanoes form
• Are all volcanoes the same
• How often do volcanoes erupt
• What hazards are associated with volcanoes
• Can eruptions be predicted or prevented

How Do Volcanoes Form

• What is a volcano
  • Eruption of magma onto Earths surface
  • Magma consists of molten rock, some crystals, and dissolved gases (mainly H₂O, CO₂, & SO₂)
  • If magma density is low, will rise through Earth toward surface
  • Eruption may involve lava (liquid rock) or pyroclastic material (particles thrown from volcano)

Where Do Volcanoes Form

• Great heat is required to melt rock, therefore volcanoes can only occur above regions in Earths interior where such heat is generated
• Occurs primarily at plate boundaries, especially spreading centers and subduction zones, and over "hot spots"

Are All Volcanoes the Same

• Nature of a given volcano depends on
• composition of the magma being erupted
  • basalt - high temperature, low viscosity
  • andesite - slightly lower temperature, more viscous, contains abundant dissolved gases
  • rhyolite - lowest temperatures, very viscous, variable amounts of dissolved gases, from almost none to extremely large amounts
• Nature and frequency of eruptions different

• Magma viscosity
  • In general, low viscosity magmas erupt more frequently and with less violence than high viscosity
• Amount of dissolved gases is a major factor in nature of eruption
  • low gas amounts yield more passive eruptions
  • large gas amounts yield explosive eruptions

• flood basalts (fissure eruptions)
  • very low viscosity, large volume, long lived - Washington-Oregon, Siberia, ocean basins
• shield volcanoes
  • low viscosity, more localized source so form volcano instead of plateau - Hawaii
• cinder cones
  • low viscosity, low volume, moderate dissolved gas content, short lived - Paracutin
  •  
• Stratovolcanoes (composite volcanoes)
  • moderate to high viscosity (andesite)
  • moderate to high dissolved gas content
  • may form lava or pyroclastic material
  • long lived, with long repose times
  • form steep-sided volcanoes with alternating layers of lava and pyroclastic material
  • most dangerous type of volcano
  • Mt. Saint Helens, May 18, 1980

• Volcanic Domes
  • very high viscosity magma
  • low gas content
  • slow forming, relatively short lived
  • may become unstable and form "glowing avalanches"
  • Mt. Saint Helens after initial eruption of May 18, 1980

• Caldera-forming volcanoes
  • "Super-volcanoes"
  • High viscosity, large volume, high concentration of dissolved gases
  • Massive eruptions of pyroclastic material
  • Infrequent, but globally devastating when they occur
  • Yellowstone

How Often Do Volcanoes Erupt

• Frequency of eruption related to
  • rate of magma production
  • viscosity of magma
  • rate of crystallization and cooling
• Basaltic volcanoes (Hawaii, Etna) - every decade or so
• Composite volcanoes (Mt. Saint Helens) - decades to centuries

• Caldera-forming volcanoes - millenia
  • Mt. Mazama (Crater Lake, Oregon) erupted approximately 5,000 years ago
  • Long Valley Caldera (California) gave some indications of erupting a few years ago
  • Estimated that Yellowstone erupts approximately every 600,000 years; last eruption was approximately 600,000 years ago!

What hazards are associated with volcanoes

• Lava
  • molten rock that incinerates organic matter in its path
• Pyroclastics
  • ash - fine particles
  • lapilli - granular particles
  • bombs - larger particles of various shapes

• Lahars (mudflows)
  • mixture of fine volcanic rock and water (from rain, melted snow, melted glacier)
  • pose a threat long after the eruption has stopped
• Pyroclastic flows (Nuées Ardentes)
  • very hot cloud of volcanic ash and expanding gases flowing rapidly down the slope of the volcano

• Toxic Gases
  • sulfurous gases
  • carbon monoxide
  • hydrochloric acid
  • carbon dioxide (Lake Nyos, Cameroon)
  • steam (Krakatoa)

• Large volcanic eruptions capable of altering global climate
  • 1816 - Year Without A Summer
  • 1991 - Eruption of Mount Pinatubo lowered global temperature by approximately 0.5 °C
  • Chemistry of volcanic gases may have negative impact on ozone layer

Volcanic Prediction

• Volcanoes categorized as
  • Active - have erupted in historic times and considered capable of additional eruptions
  • Dormant - has not erupted in historic times, but looks relative fresh and assumed capable of erupting again
  • Extinct - old, eroded volcano believed incapable of erupting again

• This categorization is not very precise, and often wrong
  • "extinct" volcanoes may simply be dormant
  • frequency of eruptions varies over wide time span; difficult (impossible) to know for certainty average recurrence interval for every volcano
  • probability may increase, not decrease, with lack of eruption over a given time span

• Long term prediction based on
  • careful geological mapping of volcanic deposits
  • age determinations of pre-historic eruptions
  • detailed monitoring of a given volcano
• Short term prediction based on monitoring
  • precursor activity (earthquakes, change in hot springs or geysers, composition of gases)
  • ground deformation (tilt meters)

Prevention

• Can volcanoes be prevented
  • No, but people have tried ingenious ways to minimize damage of volcanic eruptions
    • Icelanders sprayed water on a lava flow to divert it from a town
    • Such measures generally met with limited success
    • One person suggested plugging the vent of Mt. Saint Helens with concrete to stop if from erupting!

Streams                                    Back to top

Hydrologic Cycle

• Constant recycling process of all water in, around, and on Earth
• Cycle starts: evaporation -> atmosphere -> rain/snow
  • Infiltration -> groundwater
  • Evaporation/transpiration -> atmosphere
  • Surface runoff -> to ocean
• Cycle starts over
• 100 billion gallons/year cycle through system
• 100,000s years for transit

Streams

• Water flowing in a channel
• Drainage Basin - Area drained by a stream

Stream Discharge

• Flow volume during a time period (gal/min; ft³/sec; meter³/hour)
• D = Area X Velocity
• Factors affecting discharge
  • Rain/overland flow
    • Water coming from tributaries
    • Water running directly into stream from land
  • Base flow - from groundwater

Floodplain

• Flat area adjacent to channel
• Formation - overflow of channel during flooding
• Characteristics
  • Slopes upward from channel to valley walls
  • Uppermost part flooded only during unusually severe floods ("100 year" flood)
  • Area near channel flooded most often
• Building homes, businesses, etc. on floodplains not recommended
• Midcontinent USA flood of 1993!

Natural Levees

• Ridge parallel to channel on floodplain along both sides of channel
• Formation - sediment carried out of channel during floods
  • coarsest material deposited closest to channel - produces ridge
• Value to people: helps prevent flooding
• Artificial levees - built along channel

Erosion by Streams

• Three major types
  • Downcutting - deepening the channel
  • Headward erosion - lengthening channel at its beginning (head)
  • Lateral erosion - eroding on the sides of a stream channel
    • Meander formation and evolution
    • Plains streams: Low gradient, large floodplains -> channel migration

Sediment Transport

• Sediment transported as
  • Bed load - pushed or rolled along stream bottom
  • Suspended load - particles transported within the water column
  • Dissolved load - material in solution
• Stream Capacity
  • Total load a stream can carry

Velocity, Gradient, Base Level

• Velocity related to discharge and gradient (steepness) of stream channel
• Velocity varies along the length and width of a stream
• For same discharge, steeper gradient yields higher velocity
• Low-gradient streams may have high velocity if discharge is high
• Gradient normally decreases downstream
• Longitudinal profile of typical stream is concave-upward
• Level below which stream cannot erode is called base level
• Stream may have many intermediate base levels; sea level is ultimate BL

Meandering Streams

• Streams with highly curved paths
• Produced by lateral migration of channel
• Natural path for low-gradient stream
• Artificial straightening - expensive for large streams

Velocity and Sediment Sorting

• Higher the discharge, the greater the capacity of a stream
• Higher velocity, the larger the particle that can be moved (competency)
• Variations in velocity cause sorting of sediment load
• May lead to well-sorted sediment

Deposition By Streams

• Sediment may be deposited in many locations
  • In meandering channels
  • On floodplain during waning stages of flood
  • At mouth (end) of stream. May produce delta or alluvial fan

Deltas and Alluvial Fans

• Sediment load is deposited when stream velocity decreases rapidly
• If stream empties into a body of water (ocean, lake), sediment forms a delta
• If stream flows from mountains into dry plain or dessert, sediment forms an alluvial fan

Deltas

• Fan-shaped mass of sediment deposited where a stream flows into lake or stream
• Types of deltas
  • "Bird foot"
    • Irregular coastline, weak lake/ocean currents
    • Mississippi River Delta
• Types of Deltas
  • "Classic" delta
    • Ideally, has "delta" shape
    • Smooth, arcuate coastline
    • Strong lake/ocean currents
    • Nile River Delta
      • Aswan High Dam built in 1970 to prevent flood damage

Has caused other environmental problems

Coastal Hazards                        Back to top

Why Worry About Coastal Hazards

   30 of 50 states border an ocean, Gulf of Mexico, or one of the Great Lakes

  Approximately 85% of U.S. population lives in these states

   More people live in coastal counties than inland counties

  About half of population in states with a coastline live near the coast

Types of Margins

   Coasts may be on edge of continent at a convergent plate boundary

  Known as an active margin

   May be on edge of continent far away from the plate boundary

  Known as a passive margin

   Coastal features are different for the two kinds of margins

Differences in Coastal Margins

   Passive Margins

  Typically form wide beaches, barrier islands, deltas

   Active Margins

  Seismic activity causes land to rise or sink faster than wave action can modify it

  Forms features such as arches, stacks, sea cliffs, terraces and wave-cut platforms

Processes That Shape Coasts

   Major processes affecting coasts are tides and waves

   Tides

  Caused by gravitational effects of the Moon

  Two high tides and two low tides in period just over 24 hours

  Larger than average tides (Spring Tides) and smaller than average tides (Neap Tides) occur monthly as Moon revolves around Earth

    Waves

   Caused by wind

   Key measurements of waves are wavelength and wave height (amplitude)

   Energy is transmitted as wave, but water only moves in circular fashion

   Circular motion of water decreases with depth

   Depth below which no motion occurs is called wave base

   Wave base approximately equal to  wavelength

Processes that Shape Coasts

   Surf

  Surf forms when waves encounter sea floor at a depth less than the wave base

  Waves begin to slow down as they reach shallower water

  Water piles up as wavelength shortens

  When water reaches a certain height, it breaks, forming surf

Coastal Erosion: Sediment Transport

   Waves rarely arrive perfectly parallel to a beach

   Approach of waves at an angle to beach face means one end of wave will encounter shallow water before other end

   Leads to wave refraction, or the bending of waves

   Creates the longshore current

   Longshore Current

  Moves sediment in a zig-zag pattern that, on average, is parallel to the beach

  Movement of sediment is known as longshore drift or littoral drift

  A beach is therefore just a moving river of sand

  Must replenish sediment or starve beach

Coastal Erosion: Sediment Deprivation

   Beaches can be deprived of sediment by several causes

  Dams on rivers

  Structures built to hold sand in place

  Groins

  Breakwaters

  Jetties

   Often create greater problem than existed originally

Coastal Erosion: Headlands

   Areas that protrude into sea more subject to erosion than areas farther back

   Wave refraction concentrates energy on headland areas

   Effect is to straighten out shoreline

Coastal Erosion: Storms

   Waves are the product of wind

   Storms produce strong winds, therefore produce very large waves

   Coastal erosion more severe during storms than at other times

   Normal seasonal storms shift sediment from beach to off-shore storage, then back again onto beach

Coastal Erosion: Storms

   Major storms (hurricanes) produce far more erosion

   Storm surge

  Water is lifted up by low pressure in the eye of the storm

  Strong winds push large waves

  Barrier islands particularly susceptible because of overwash

Landslides                                 Back to top


 

Mass Movements

Mass Movement

 Downslope movements of earth materials under influence of gravity

 Slope Failure

l   Slow movement

l   Fast movement

Environmental Effects

 Relatively little loss of life

l   1970-1974, estimated 600 lives lost worldwide

l   In USA, approx. 25-50 lives lost/yr

 Extensive property damage

l   In USA, approx. $1-2 billion property damage/yr

l   Most losses are avoidable

Types of Earth Material

 Sediments

l   Unconsolidated materials - not solid rock

    Sand, gravels, clays, mixtures; other types

    In streams, on ocean/lake floors, soils, etc.

    Homogeneous throughout (ideally)

    No weak zones (ideally)

 Rocks

l   Consolidated Materials - more or less solid

l   Three major types

    igneous

    sedimentary

    metamorphic

l   Have weak zones

    fractures

    boundaries between rock types

l   Once buried deeply

    100s to 1000s of feet deep

l   Now at Earths surface

    Uplift

   slow - <<1 mm -1 cm/year

   large scale

    Erosion of overlying material

 Igneous Rocks

l   Once molten

l   Cooled and solidified beneath surface

    lava is an exception

l   Fractures

    Divides mass into large blocks

    Cooling yields volume loss

    Load reduction yields volume increase

   Uplife/erosion reduces confining pressure

 Sedimentary Rocks

l   Form from unconsolidated sediments

l   Sediments become deeply buried - slowly solidify into rock

    Pores filled with cement (new minerals)

    Pressure squeezes mineral grains together

l   Bedding Planes

    Boundary between sed. rock types

    Separate rocks into layers (beds/strata)

    Originally horizontal - may later be tilted

l   Fractures across layers

l   Weak zones: fractures/bedding planes

 Metamorphic Rocks

l   Rocks changed by heat and pressure

l   Formed deep in Earth

l   Never molten - changes occur in solid state

l   Resemble igneous rocks in hardness (usually)

l   May have parallel planes of weakness

    Often highly contorted

l   May be fractured into large blocks

Types of Mass Movement

 Slow Mass Movement

l   Creep

    Chiefly in unconsolidated, clay-rich soil & shale

    Rarely, if ever, causes loss of life

    Very slow (cm/yr) but acts over long period of time

    Uppermost surface layers involved

   Tilting of telephone poles, fenceposts, and trees

   Damage to weakly anchored constructions

    Cause: wetting -> expansion, drying -> shrinking

 Rapid Mass Movement

l   Rockfall

l   Rocks fall down very steep slopes

l   Slide

l   Cohesive mass of rock material slides down slope, often along bedding planes

    Especially where sandstone layer (porous/permeable) overlies shale layer (low permeability)

    Water moves along shale; acts as a lubricant

    Sandstone mass slides downslope

l   Slump

    Short distance movement down slope

    Curved fracture surface separates slump block from stable mass

    Backward rotation of slump block

    Common in unconsolidated or homogeneous materials

l   Flows

    Down slope movement of earth materials +/- water

    Mudflows - much water

    Earthflows - little water

    Debris flows - little water; mixture of rock, soil, etc.

    Chaotic particle movement - like water molecules in stream

l   Subsidence

    Vertical downward movement along steeply inclined fractures

    Caused by collapse into underground void space created by

   dissolution of soluble rock - caves

   mining activities

   groundwater withdrawal

Causes of Mass Movements

 Factors Preventing Mass Movement

l   Friction - decreases with increase in slope angle

    Angle of repose

   size, shape, and uniformity of particles

   water

    Cohesion

   forces holding particles together

   cohesion reduced -> mass movement downslope

Prevention of Damage by
Mass Movement

 Avoid areas with signs of potential movement

l   especially areas with cracks in the earth

 Reduce slopes

 Reduce loads

 Anchor rocks

 Remove water from potential movement zone

END

Global Climate Change             Back to Top

Climate vs. Weather

• Weather: physical description of the atmosphere
  • Temperature
  • Humidity
  • Wind speed and direction
  • Barometric pressure
• Climate: A description of the long-term pattern of weather for a region
  • Arid
  • Tropical
  • Monsoon
  • Temperate
• Polar

What Controls Climate

• Regional climate is the product of many factors
  • Latitude
  • Arrangement of land masses relative to oceans
  • Location of mountains
• Global climate controlled mainly by insolation (incoming solar radiation)

Effect of Latitude

• Solar radiation greatest in tropics
  • Air at low latitudes warmed, causing it to rise
  • Displaces air that has cooled, causing it to sink
  • Air at poles cooled, causing it to sink
  • Displaces air that has warmed, causing it to rise
  • Establishes a series of convection cells

Effects of distribution of land masses vs. oceans

Is the climate changing

• What is evidence of current climatic changes
• Can we evaluate the effect of different forcing agents on climate change
• Can we separate natural climate change form human-induced climate change
• Does it really matter what causes climate to change

Atmospheric Gases: The Greenhouse Effect

Modern Records of CO₂

Atmospheric CO₂

• Modern records show a persistent rise in atmospheric CO₂
• Is this rise the result of natural causes or human activity
• What climate proxy can be used to evaluate natural fluctuations

Glacial ice in Greenland and Antarctica contain trapped air

which can be analyzed in the lab

Anthropogenic heavy metals

Effects of volcanic eruptions

• Large pyroclastic eruptions inject ash and droplets of sulfuric acid into stratosphere
• Block sunlight, therefore reduce insolation
• Can remain in stratosphere for several years

Evidence of Past Climate Change

• What natural processes are affected by climate
• Which of these can be preserved in geological record
• What principles can be used to interpret these records
• Dendrochronology (tree rings)
  • Trees grow new material each year
  • Rate of annual growth dependent on physical conditions and amount of nutrition
  • Rapid growth yields thick annual ring, slow growth yields thin annual ring
  • Slow growth records environmental stress (fire, drought, insect invasion, temperature change, etc.)

Dendrochronology

• Trees produce annual growth rings

• Rings in this tree indicate it was over 1600 years old when it died

• Cores from different trees that overlap in age can be cross-correlated to expand the record

• Environmental catastrophes can be dated with tree rings

Pollen

• Different plants grow in different climatic zones. Pollen from these plants is dispersed and deposited as sediment in the local area

• Pollen from different plants is distinctive; can determine type of vegetation that grew in an area by identifying pollen in sediment

El Niño

Effects of El Niño

Are there records of past El Niño events

Coral Reefs

• Coral grows in warm, shallow water.

Coral appears to be a single living thing

but is really a colony of many individuals, called polyps.

Coral

• Coral reefs grow by individual polyps raising themselves through deposition of calcium carbonate at their bases
• Composition of growth rings is a function of sea surface temperature
• Compositional variation in major element chemistry, i.e., substitution of different elements for Ca in CaCO₃
• Compositional variation in isotopic composition of oxygen in CaCO₃ (¹⁶O vs. ¹⁸O)
• Cores are taken from a living reef
• Growth rings are marked to be analyzed for isotopic and elemental compositions

Isotopic composition of coral vs. sea surface temperature

Cd/Ca and Ba/Ca vs. SST

350-year record from coral

Ice Ages

Possible causes of Ice Ages:

The Milankovich Theory

Seasons are caused by revolution of inclined Earth around Sun

Orientation of spin axis, axial tilt, and shape of orbit change over time

Periods for these changes vary from 22,000 years to 400,000 years

Precession: Change in orientation of axis with period of 22,000 years

Eccentricity

• Shape of Earths orbit changes with time, from nearly circular to more elliptical, with one at a period of 100,000 years and another at 400,000 years

Variations in axial tilt with period of 41,000 years

Combination of oribital effects causes major variations in insolation

Potential effects of global climate change

• Greater variability in weather
  • severe droughts in some areas, extensive flooding in others
• Reduction in ocean productivity
• Melting of ice caps
  • rise in sea level
  • flooding of low-lying regions

Effect of melting existing glaciers on sea level

Regions of U.S. that would be flooded by 10-meter rise in mean sea level

Some localities would be totally flooded

END

Resources                                Back to top

n    All things necessary or important to human life and civilization

n    Resources change with time:

   Mercury - resource today, but not in primitive societies

n    Two major types of resources: renewable and non-renewable

   Renewable: food, water (within historic time)

   Non-renewable: petroleum, metals (mill. yrs. to renew)

Resources and Reserves

n   Reserves

  Amount found and economically usable with existing technology

n   Resources

  Total amount on and in the Earth

  Includes both already found and still undiscovered

Resources and Reserves

n   Conditional (Subeconomic) Resource

   Amount that has been found but too expensive to utilize with existing technology

n   Petroleum in oil fields

   50-60% in old depleted fields is still in ground

   Too expensive today, but OK at higher prices

n   Undiscovered (Hypothetical) Resource

   Amount expected to be found but not yet discovered

Water as a Resource

n   Hydrosphere

  All water in, on, and around Earth

  Includes water in atmosphere, underground, and above ground

n  Water vapor, ice in glaciers/snow, and surface/subsurface water in lakes and streams

Ground Water
(Subsurface Water)

n   Sources

  Infiltration of water into Earth

n  rain, streams, ocean

  From Earths interior - some may be original

n   Character

  Fresh, saline with variable amounts of dissolved materials

Runoff and Infiltration

n   Runoff

  Water flowing over land surface and in streams

n   Infiltration

  Water moving through rock material

n  Dependent on porosity (percent of void space in earth material) and permeability (speed that water flows through earth materials)

Representative Porosities/Permeabilities

Terminology

n   Zone of Aeration (also called the Vadose Zone)

  Zone near Earths surface where pores and openings in rocks are unfilled or partly filled with water

n  Subsurface water, but not groundwater

n  Also called soil moisture

Terminology

n   Zone of Saturation (Phreatic Zone)

  Zone below the aerated zone in which all pores and openings are water-filled

n   Groundwater

  Water in the zone of saturation

n   Water Table

  Boundary between zones of saturation and aeration

Water Table

n   Occurs only in unconfined aquifers

n   Surface usually not flat

  usually undulates with the surface topography and with other factors

n   Distance below ground surface changes with rainfall amount

Recharge

n   Processes that replace and increase water in the zone of saturation

n   Sources

  Infiltration from ground surface

  Water movement within the ground from other locations

n   Slow underground movement, esp. in deep systems

  10s to 100s years to migrate a few miles

Aquifer

n   Rock or sediment with high porosity and permeability Water withdrawal possible in large amount, quickly

n   Chiefly sandstones, unconsolidated sands and gravels

n   Limestones with interconnected solution channels and fractures

Aquiclude

n   Material with low permeability and very slow water movements

n   Unweathered, unfractured igneous rock

n   Limestone without fractures, caves, or connected voids

n   Shales

Aquitard

n   Earth material with relatively low permeability and relatively slow water movement

n   Between aquifer and aquiclude in permeability

n   Example: sandstone with pores partly filled with clay

Aquifer Geometry

n   Unconfined Aquifer

  An aquifer overlain by permeable earth materials

  In well, water rises to top of water table

  Recharge from

n  ground surface directly above water table

n  other locations by lateral flow

  Water flows out without pumping only where WT intersects Earths surface

n   Confined Aquifer

  Aquifer bounded above and below by aquicludes/aquitards

  Recharge only from lateral inflow of groundwater from other areas (recharge areas)

Artesian Well

n   Recharge area at higher elevation than top of confined aquifer water surface

n   Water will flow upward in well without pumping

n   Artesian system - entire groundwater system associated with artesian conditions

n   If recharge area is higher than ground elevation where well is drilled, water may flow onto the ground without pumping

n   Potentiometric Surface: elevation up to which water will move in artesian system well

Aquifer Geometry

n   Perched Aquifer/Water Table

  Localized layer of impermeable material within an otherwise permeable material

  Water temporarily trapped above this layer

  Perched aquifers cannot usually sustain high well yields because of their limited extent

Terminology

n   Effluent Stream

  Stream which gains water from groundwater

  Zone of saturation intersects stream channel

n   Influent Stream

  Stream which loses water into ground

  Zone of saturation beneath stream channel

Effects of People on Groundwater Resources

n   Reduction in Recharge Rate

  Urbanization - reduces permeability of recharge areas

  Destruction of vegetative cover - reduces infiltration

n   Loss of producing water wells by pumping

  Cones of depression

  Magnitude of effect - recharge rate/withdrawal rate

n  Withdrawal rate>recharge rate - cones become deeper, may overlap with other cones, may lower groundwater table over large area

n  If zone of saturation is lowered enough, aquifer may be essentially depleted in water

n  Permanent destruction of aquifer possible - subsidence

  Major problem in Nebraska, western Kansas, west Texas, and adjacent states (The Ogallala Aquifer System, p. 242 of textbook)

n  Water loss may destroy irrigation farming in these areas

n   Land Subsidence

  Lowering of water table removes water from pores in sandstones and other aquifers

  Loss of support of sand grains by water causes collapse into voids - sand becomes closer packed -> land subsidence

  Pores permanently lost - aquifer destroyed forever

n   Salt Water Intrusion

  In coastal areas

  Freshwater zone of saturation replaced by seawater

  Produces unusable water

Alleviation of Groundwater Supply Problems

n   Conservation

  Fairly minor effects except in localized crises of extremely dry weather for long time

n   Changing farming practices

  Irrigation farming - major user of groundwater supplies

  Perhaps long-term solution - relocate irrigation farming into wetter areas of USA

n   Transfer of water from one area to another - pipelines

  Directly on land in place of groundwater

  Recharge groundwater reservoirs

  Example: California - 150 mil. Gallons from E. slopes of Sierra Nevada to Los Angeles

  Economic/political problems, expensive

n   Artificial Recharge Basins

  Hold surface water

n  Minimizes runoff

n  Allows water to infiltrate into groundwater supply

n   Desalinization

  Removal of salt from seawater and/or brines

  Expensive

  Economical on relatively small scale - not appropriate for national supply

END

Soil as a Resource                Back to Top

What is soil

      Geologists:

     A zone of weathered rock preserved in the geological column

      Engineers:

     Any unconsolidated material that overlies bedrock

      Soil Scientists:

     Materials currently (or formerly) at the earths surface that are capable of supporting plant growth

Why is soil
an important resource

     Do you eat

     Do you like clean water in rivers, lakes, and the ocean

     Do you drive on highways

The Spatial Scales of Soils

What are soils composed of

     Minerals

     Organic Matter

     Water

     Air

Three Morphological Properties of Soils

     Color

     Texture

     Structure

Color

     Color often good indicator of composition

       Black soils tend to be rich in organic material

       Red soils are likely to be rich in insoluble iron oxides (hematite)

      Light-colored soils may be rich in sand


 

Texture

     Texture refers to the size of soil particles

    Classified on percentages of sand, silt, and clay

    Loam is a mixture of all three particle sizes

    Use modifiers to describe combinations (e.g., silt loam, sandy clay loam)

Soil textural classes

Clay Minerals

Structure

     Refers to soils tendency to form peds, i.e., natural aggregates of particles

     Soils with very large peds separated by large cracks have low water-holding capacity

     Organic material tends to cause aggregation of soil particles into crumb-like peds

     Soils with no peds are more easily eroded

Fecal pellets: earthworms

Clay Coating in Pore

Porosity and Permeability

Roots get nutrients and water
from the soil

Humification of plant tissue

Soil Horizons

     Topmost layer: A Horizon

    consists of minerals plus added organic material from decaying plant tissue

     Next layer: B Horizon

    enriched in clays washed down from horizon above

     Below this is the C Horizon

    Weathered but otherwise undisturbed material above bedrock

How can soils be distinguished from one another

     Morphological Properties

   Color

   Texture

   Structure

     Sequence of Horizons

Why do soils differ from one another

     Parent material

     Topography

     Vegetation

     Climate

     Time

Horizon Development: Climate and Vegetation

World Climate

World Biomes

Native Prairie in North America

Top Four Processes of Soil Degradation in U.S.

     Water and Wind Erosion of Cropland

     Salinization of Irrigated Soils

     Pollution

  Organic chemicals and metals

     Urbanization

Additional Processes of Soil Degradation Worldwide

     Deforestation

     Overgrazing

     Desertification (Climate Change)

Erosion

     Physical removal of material from one place to another

     Caused by movement of soil and rock particles by water, wind, and ice

     Water most effective erosive agent

     Rainfall loosens soil particles; runoff and wind carry away loosened soil

Erosion Basics

      Size of particle that can be moved is dependent on velocity of transporting medium (water or wind)

      Greater the velocity, the larger the particle that can be transported

      Much water erosion occurs during floods or high-intensity rainfall

      Steep, unvegetated slopes are especially susceptible to water erosion

      Flat, unobstructed land is more susceptible to wind erosion

Wind Erosion

Strategies For
Reducing Erosion

     Main strategies

    reduce velocity of water and wind over ground surface

    protect soil from the effects of water and wind

     Reduction of wind velocities

    Wind breaks

    Strip cropping

Natural Desertification

Deforestation and Overgrazing

Combating Desertification

      Building barriers (fences) to prevent advance of sand dunes in Africa

Salinization

      Accumulation of salts in soil.

      Salinization occurs in warm and dry locations where soluble salts precipitate from water and accumulate in the soil. Saline soils are common in desert and steppe climate. Salt may also accumulate in soils from sea spray. The rapid evaporation of salt-rich irrigation water has devastated thousands of acres of land.

Pollutants in Soils

     Where are they held in the soil

     How easily can they be released to soil water

     How easily can they be degraded by microorganisms

END

Mineral Resources                Back to Top

     Resource: Total amount of a mineral on Earth.

  Only a small fraction of resources are economic

  Metals need to be concentrated

  C.F. = concentration of metal in ore/concentration of metal in average crust

     Reserves: Amount of resources that are economic

  Reserves are taxed in U.S., so estimates are low

Types of Mineral Resources

     Metals

  Precious metals: gold, silver, platinum

  Base metals: iron, aluminum, lead, copper

     Non-metals

  Industrial minerals: kyanite, clays, talc, sulfur, quartz, feldspar

  Construction & ag minerals: limestone, sand & gravel, gypsum

Mineral Deposits

     Metals require concentrating by natural processes

  Rare metals (gold, platinum) require high concentration factors

  May be economical at low absolute concentrations

  Common metals (Fe) require less concentration

  Nature of the deposit is important (oxide, sulfide, silicate, carbonate, etc.)

     Most material removed during mining is non-economic waste (gangue)

     Separation of ore from gangue is expensive

     Disposition of gangue is serious environmental problem

     Environmental regulations raise costs

  Cost of reclamation may exceed value of ore

     Unregulated foreign deposits cheaper to mine

Distribution of Mineral Deposits

     Concentration of metals means that some places will have much more than others

     Distribution of ore will not be uniform

     Very rare metals may occur in economic deposits in only a few places in the world

     Every country dependent on others to provide at least some of its mineral needs

     Greater the needs, more dependent a country is on foreign trade

Formation of Ore Deposits

     Magmatic Deposits

   Pegmatites: very coarse-grained rocks

    Contain large crystals - easy to mine

    Typically concentrate select rare elements (B, Be, Li, Ta)

    Often contain gem-quality minerals (emerald, aquamarine, tourmaline, topaz)

   Settling of dense minerals (chromite, magnetite)

   Transport of minerals from great depth (diamond)

   Sublimation of sulfur from hot volcanic gases

Formation of Ore Deposits

     Hydrothermal deposits

   Form by solution of metal in hot water, then precipitation when water cools or reacts with surrounding rock

   Mo, Cu, Pb, Zn

     Black Smokers

  Hydrothermal emanations from mid-ocean spreading centers

  Sulfides deposited when hit cold sea water

Formation of Ore Deposits

     Sedimentary Processes

  Placer Deposits

    Settling of dense minerals in gravel deposits (gold, diamond)

  Banded Iron Formation:

    Oxidation of soluble Fe²⁺ in Precambrian oceans to insoluble Fe³⁺ by oxygen given off by marine organisms

    Form worlds largest iron deposits (ex: Mesabi Range in Minnesota)

  Limestone, clays, sands and gravels

  Evaporites

    Gypsum, halite, other salts

  Weathered deposits

    Bauxite (aluminum ore), laterites (iron ore)

  Marine deposits

    Submerged placer deposits

    Manganese nodules on sea floor (Mn, Cu, Pt, Co, Ni)

Mineral Consumption

     How has mineral consumption in U.S. changed since 1776

     (In-class exercise)

The Future

     U.S. totally dependent on other countries for much of its mineral needs

  Imports 100% of several important metals

  Many mineral commodities imported even though we have reserves in U.S. because of costs

  Requires diplomacy to maintain trade with many nations supplying our needs

     Historical Trends

  Conservation

  Recycling

     Cost of mineral resources

  Price will increase with time

  Inflation

  Large deposits worked first

  Smaller deposits much more expensive to mine

  Increased environmental regulations

  Only improvements in methods of processing ore from gangue causes price decrease

     Plate tectonics provides a model for searching for new deposits

  Old plate reconstructions

  Understanding the types of deposits that form from igneous, sedimentary, and metamorphic processes

     New methods being employed in search for mineral deposits

  Remote sensing

     Environmental impact of mining activities

  Underground mines

    Collapse of surface may occur many years after mining has ceased (and mining company has disappeared)

  Strip mines

    Reclamation efforts expensive

    May not produce desired effects

  Tailings often source of pollutants

END

Energy Resources                Back to Top

Global Energy Requirements

n   Dramatically increased since 1850s

   Mostly since 1945

n   Major changes in sources

   Pre-1850s - wood

   Today - 70% petroleum

Changes in Energy Sources in USA, 1850-1980*

Energy Requirements and Demographic Changes

n   Factors increasing energy use

   Increasing populations

   Increasing technologies

n  Energy needs increase

n  Fuel type changes

n   Future energy requirements of world

   World pop. effects->energy needs increase

   Development of lesser developed countries:

n  More technology->further energy need increase

n  Most of growth of world energy use over last decade

Cost of Future Energy

n   Costs will increase unless new fuel sources found

   Hardships, especially in lesser-developed countries

   After 1970s oil price increase - increased debt in less-developed countries

Fossil Fuels

n   Fossil

   Remains of past life

n   Fossil Fuels

   Fuel from plants and animals of geologic past

n   Era of Fossil Fuels started in 1880s

n   Will probably end in 2100-2200

n   What then

Types of Fossil Fuels

n   Coal

n   Petroleum/natural gas

n   Oil shales

n   Tar sands

n   Peat

General Comments

n   Formation takes long time - millions of years

n   Occurs in rocks several million years old

n   Organic material must accumulate in large amouts

n   Must be buried quickly

   Unstable in presence of air and bacteria

   Requires subsidence of Earths surface

   Long-continued sediment deposition

n   Types of organic material forming fossil fuels

   Oil/gas - chiefly microscopic animals that lived in ancient seas

   Coal - chiefly plants living on land

n   All major fossil fuels formed deep within the Earth

   High burial pressures and temperatures altered original organic material

Oil and Natural Gas

Requirements for Formation

n   Accumulation of large numbers of micro-organisms

   Chiefly in shallow oceans adjacent to land - high biotic activity

n   Subsidence of ocean floor - rapid burial

   Accumulation of thick mass of sediments

n  Dark-colored from organic carbon

n  Clays, silts, sands

n  Called SOURCE BEDS for petroleum/natural gas

n   Deep burial

   Chemical reactions at high temperature and pressure

n  Petroleum begins forming

Changes in Petroleum During Burial

n   Earliest petroleum is very thick - like asphalt

n   Deeper burial: higher temperatures -> less viscous oil

n   At still higher temperatures: petroleum -> natural gas

   Reason why petroleum and natural gas often occur together

n   Even higher temperatures: destruction of petroleum and natural gas

Migration into Reservoir Rocks

n   Source rocks (black shales chiefly) are impermeable

   Petroleum cant be pumped out of ground

   Luckily migration occurs into porous/permeable rocks

n  RESERVOIR ROCKS

n  Chiefly sandstones/limestones with high porosity

n   Migration continues to impermeable rock barrier

    Called CAPROCK

    Shales, impermeable limestone, buried lava, etc

    Petroleum/gas accumulates at barrier

n   Petroleum traps - location where further migration prevented by barrier

    Many traps caused by faulting and folding

n  Folds - chiefly anticlines & domes in sed. Rock

n  Faults - breaks with movement along break

n  Other types - often hard (=expensive) to find

Oil and Gas Separation

n   Natural gas migrates faster and easier than liquid petroleum

n   Often gas separated from petroleum

   Results in gas fields with little oil

Global Distribution of Oil & Gas

n   Uneven distribution

   Some countries (e.g., Japan) have none

   Other countries (e.g., Saudi Arabia) have much

   Ten countries have > 80% of world reserves

n   Most oil-wealthy countries produce much more petroleum than they use

n   Other countries (e.g., USA) use much more than they produce

n   USA Reserves = 22 billion barrels as of 1998 (1 barrel = 42 gallons)

n   USA uses 6.5 billion barrels/year (1998)

n   Total reserves completely gone in 3.3 years if constant use and USA used only it own oil

Proven World Reserves of Petroleum

Age of Petroleum Resources

n   Two ages to consider

   Age of source rocks (= age of oil/gas)

   Age of reservoir rocks where oil/gas accumulate

   Reservoir rocks usually younger than oil/gas

n   Most oil/gas formed and occurs in rocks between about 1 million and 200 million years old.

   Oil > 200 million years old:

n  Destroyed by high temperatures

n  Lost by migration to Earths surface

   Oil < 1 million years old:

n  Hasnt had time to form completely - incomplete chemical reactions

Future World Oil Production

n   Shortages and depletion

   Shortages - lack of oil caused by political/economic decisions

n  1973, 1978 shortages - largely produced by OPEC countries

n  August 1990 - Iraq invades Kuwait

   Oil price goes from $18/barrel in July to $35/barrel in October

   Price dropped back again soon

n   Depletion

   Lack caused by using up oil/gas reserves

   No oil/gas unless substitutes found (e.g., liquification of coal)

   Time of major depletion - hard to tell exactly

n  Discovery of new oil/gas fields - increases resource base

n  New recovery methods - change resources into reserves

n  Price increases - change resources into reserves

n  Conservation

n  Substitution of other fuels

n  Increased technology in underdeveloped countries - increases use

   25 years (50 years max)

Coal

Formation of Coal

n   From plant remains accumulated in vast swamps

   Swamps persisted for many (thousands) of years

   Many along ancient coast lines

n   Climate

   Cool temperate, much rain

   Not tropical

n  Modern tropical forests: high temp., heavy rain

n  Decomposition too rapid; little organic material accumulates

n   Rate of accumulation

   Today, peat (source of coal) accumulates at 1 mm/year (variable)

   Layer of peat 10 meters (30 feet) thick takes 10,000 years to accumulate

   Peat -> coal: much volume loss

   10 meters of coal takes >> 10,000 years to form

   Subsidence of swamp land

n  Necessary for thick accumulation of plant remains

   Burial by more plant remains, later by sediment

n  Plant remains -> peat

   At or near ground surface

   Cellulose decomposes, water lost, and carbon concentrated (residual concentration)

   Takes a few hundred years

n  Peat -> coal (coalification)

   Requires high temperatures and pressures

   Progressive changes occur (increase in rank)

    Sequence: peat -> lignite (brown) coal (low rank) -> bituminous (hard) coal -> anthracite coal (high rank)

   Water, oxygen, hydrogen, nitrogen and other plant substances lost

   Carbon enriched - high rank, more carbon, higher heat content

Characteristics of Coal

n   No migration, unlike oil/gas

n   Energy content varies with degree of coalification

   Peat: least heat/unit wt. & least carbon

   Anthracite: most heat/unit wt. & most carbon

n   Many coal deposits contain sulfur

   Low S coal: <0.6% S; high sulfur coal >1.7% S

   Most USA coals relatively low in S; interior USA coals often high in S

   Sulfur sources

n  Inherited from original vegetation

n  Derived from seawater in coastal swamps

   Environmental problems

n  Acid rain

n  Acid mine drainage

n  Acid soils

   Mining methods

n  Deep buried - underground mines

n  Shallow depths - stripping methods

   Stripping: sediments/rocks over coal is removed

   Coal mined from pit

   Usually < 70 feet burial depth

   Destructive of land surface

   Expensive reclamation

   USA - 60% strip-mined

Distribution of World Coal

n   Unevenly distributed

    Mid-East and most of Africa lack deposits

    North/South America, Europe, former USSR has much

n   United States coal: four major areas

    Appalachian Mountain area (PA, WV, OH)

    Midwest area (IA, IL, MO, KS, OK)

    Northern Rocky Mtns area (MT, WY)

    Southern Rocky Mtns & desert area (CO, NM, UT, AZ)

    20 states have significant coal deposits

World Recoverable Coal Reserves

Future of Coal as Energy Source

n   Much more coal than oil/gas

   Known reserves: about 1,000 billion tons

   Total reserves (most probably mineable): 10,000 billion tons

n   USA has enough (200 years) coal reserves for all our energy needs

   But, coal cant currently be used for all energy needs - automobiles, etc.

n   Numerous Problems

   Acid production

n  If sulfur is present, burning creates SO₂ and SO₃ gas

n  SO₂ - SO₃ + H₂O = H₂SO₄ (sulfuric acid)

   Acid rain

    All rain is acidic, but sulfuric acid produces much more acids

    Clean coal before burning - not always effective

    Some sulfur hard to remove - increases costs

    Remove sulfur gases in smokestakes (precipitators, scrubbers) - increases costs

   Acid produced during coal mining when rain infiltrates into coal mines and waste piles

    Bacteria and air produce sulfuric acid

    May affect rivers, lakes, groundwater, and soils

    Reduced by covering spoil piles with soil (excludes air)

   Ash waste material

n  Ash solid matter left after burning coal

   Chiefly mineral matter - sand, clay deposited with plant remains

   May contain toxic heavy metals. Disposal problem

n  Some goes into air: widely dispersed. Dangerous

Unconventional Fossil Fuels

n   Oil Shales

   Not necessarily shale

   Doesnt necessarily contain oil

   Keragon

n  remains of plants, algae, bacteria

   Not easily utilized resource

n  keragon widely dispersed

n  huge volume of rock needed for small amount of keragon

   Most near surface in arid parts of USA

n  Requires strip mining to extract

n  Difficult to reclaim land

   not much water

   soil not very fertile

   In situ methods

n  Retorting

n  Expensive

n  Causes volume increase

n   Tar Sands

   Thick, semisolid, tarlike petroleum

n  May be immature petroleum

n  May be residue after lighter (more volatile) compounds have migrated away

n  Too thick to flow out of rock

n  Must be mined from crushed rock, like oil shales

n  Same environmental problems as oil shale

n  Most tar-sand deposits are in Canada

n   Gas Hydrate

   Solid compound formed from methane (gas) and water (liquid or gas)

   Found in Arctic regions and in marine sediments

   Require cold temperatures or high pressures

   May contain more carbon than all other fossil fuels combined

   How to get it out

n  Cant be pumped

n  Unstable at high temperatures/low pressures

   Environmental problems

n  Produces methane, a greenhouse gas

END
 

Alternative Energy Sources            Back to Top

Current Energy Usage

• Fossil fuels presently account for approximately 90% of world energy production
• Fossil fuels being extracted faster than they are being produced
• Cannot last indefinitely - replacements must be found
• Energy required for heating, cooling, transportation, manufacturing, agriculture
• Consumption varies considerably by location

 Future Energy Needs

• Demand for more energy will increase as population increases
• Energy efficiency will help, but still requires consumption:
  • material to build new cars, furnaces, etc.
  • energy to run plants that build cars, furnaces
• Increased standard of living puts more demands on energy resources

Comparative Fuel Efficiency in Transportation

Alternative Energy:
Nuclear Power

• Two kinds of nuclear reactions:
• fission - splitting of atomic nuclei into smaller ones, with release of energy
  • "dirty"
• fusion - combining smaller nuclei into larger ones, also releasing energy
  • "clean"
• Much work being done to develop fusion, but not currently feasible; only fission presently viable

Nuclear Fission

• Nuclei of U-235 will undergo fission when struck by high-energy neutron
• Fission produces lighter nuclei, energy, and additional neutrons
• Additional neutrons strike other U-235 nuclei, inducing them to fission
• Produces chain reaction
• Heat generated that ultimately produces electricity

 Nuclear Fission

• Only about 0.7% of natural uranium is U-235
• Requires refining and enrichment of natural uranium
• Fuel rods of enriched uranium have finite useful lives
• Remain radioactive, just cannot produce enough energy to produce electricity
• Spent fuel rods pose significant environmental problem

Limitations of Uranium

• Uranium reserves highly dependent on the market price of "yellowcake" (processed uranium oxide)
• Using present nuclear reactor technology, U.S. reserves can only be increased by about 4 times
• At best, could only supply about 15% of U.S. energy needs
• Would use up all domestic reserves within a few decades

Extending Nuclear Fuel Supply

• U-235 is rare isotope
• U-238 much more abundant, but not fissionable
• U-238 produces plutonium-239 when it absorbs a neutron; U-239 is fissionable
• Breeder reactors maximize production of plutonium-239, then reprocess spent fuel cells
• Technology is complex and expense
• Plutonium is extremely toxic substance!

 Hazards of Nuclear Energy

• Disposal of spent fuel cells
• Decommissioning of old reactors
• Nuclear accidents
• Core meltdown (The China Syndrome)
• Three Mile Island (1979)
  • Partial loss of coolant with 35-40% meltdown
• Chernobyl (1986)
  • Release of radioactive material into atmosphere
• Sabotage by terrorists

Nuclear Fusion

• Forming one helium nucleus from two hydrogen nuclei
• Process that occurs in Sun
• Much cleaner than fission
• Much research being done to test "cold fusion"
• temperatures required to make hydrogen nuclei fuse much greater than any vessel can withstand
• Some claims, but nothing yet proven

Solar Energy

• Energy directly from sunlight
• Two types of solar heating: passive-solar heating and active-solar heating
• Passive-solar heating
  • media (water, bricks, concrete, etc.) store heat when Sun is shining, release heat through conduction when Sun is not shining
  • requires no mechanical assistance

 Solar Energy

• Active-Solar Heating
  • Involves pumping solar-heated water from solar collectors to a storage tank or a heat exchanger
• Solar Electricity
• Uses photovoltaic cells to convert sunlight to electricity (about 20% efficient)
  • Clean but expensive - will only become common when economically feasible

 Geothermal Energy

• Temperature increases with depth, but not uniformly at every location
• Greater magmatic activity near plate boundaries, therefore more potential for geothermal power
• Areas with active geysers often utilized
  • Iceland, Italy, Japan, New Zealand, California
• Hot-dry rock program attempted to expand geothermal capability to areas without geysers

 Geothermal Energy

• Problems and limitations
  • geyser fields have limited life as hot water is used up and replaced by cold water
  • often in areas of active earthquakes; shifting faults can change flow of groundwater
  • dissolved material clogs pipes rapidly
  • can only be used in nearby vicinity - cant ship long distances

Geothermal/Heat Pumps

• Heat pumps are becoming more popular way of heating and cooling residential and commercial businesses
• Use near-constant temperature of Earth at shallow depths to cool in summer and heat in winter
• Clean and renewable source of energy
• High up-front costs, but reduced energy costs means long-term economy
• http://www.econar.com/econar.html

Hydropower

• Utilizes energy of falling or flowing water
• Primarily used to generate electricity
• Requires large volume of water moving rapidly
• In U.S., hydroelectric projects rely on large dams to impound water
• In Scandinavia, use tunnels under glaciers
• Clean, renewable power source, but has environmental consequences
• Tidal Power

 Wind Energy

• Utilizes moving air currents to drive machinery (e.g., pumps) or electrical generators
• Centuries-old concept, but not widely used today
• Wind not uniform:
  • in location (some places more windy than others)
  • in intensity (calm days vs. blustery days)
  • Presents storage problems

May be suitable for midwest U.S., including Iowa

END

Waste Disposal                    Back to Top

Classification of Wastes

     Degree of Toxicity

  Non-hazardous waste

  Hazardous waste

    Often non-hazardous waste contains some harmful substances

     Physical Nature

  Solid Wastes

  Liquid Wastes

Solid Wastes

     5 billion tons/year in USA alone

     Agriculture + mining and processing > 80%

     All other industries: 3% of total solid waste

     Much not toxic, but often some hazardous components present

     Very large volumes - where to put it

Liquid Wastes

     Smaller volume than solid wastes

     Many very toxic - chemical or nuclear wastes

Methods of Disposal

     Dilute and Disperse

    Major method during early days of industrial development

    Method: dump liquid/solid wastes where diluted and/or dispersed

    Liquid waste dumped into river, lake, ocean

   Water-soluble liquid wastes dissolve

   Water-insoluble: sink to bottom & decompose/become buried or float & disperse

    Solid wastes dumped on land at different locations or in water like liquid wastes

    Suitable for small amounts of wastes

    Still done today but now large amounts - problems

     Concentrate and contain

   Concentrate waste as much as possible (compacting, burning, chemical treatment)

   Seal concentrated waste into totally closed environment

    Example: toxic chemical in sealed metal drums, stored above ground or buried.

   Major problem: long-term containment without leaking

    Some wastes very toxic and long-lived (some nuclear wastes > 10,000 years; toxic metals last forever)

     Treat and Reuse

  Treating to obtain useful product

  Advantages

    Reduces resource depletion

    Solves waste disposal problems

  Disadvantages - costs

    Some wastes - easily and fairly cheaply processed

    Others - very expensive processes

     Export Waste Products

  Dump wastes in relatively unpopulated areas

    Western USA

    Foreign countries: industrialized countries pay undeveloped countries for right to dump waste

   Political fallout - exploitation of poor countries

   Not ethical for highly toxic substances

    Rocket transport to outer space

   Expensive

   Risky - rocket failure

Solid Waste Disposal

     Agriculture and mining activities

  Agricultural waste probably not major problem

    Decompose quickly - short life

    Low degree of toxicity (bacteria)

    Exceptions are high-density feedlots - odor, stress on environment

  Mining wastes (such as spoil piles) may be major problem

    Acid formation, toxic metals

     Municipal Solid Wastes

   Relatively small in quantity

   Disposal important - clearly associated with large numbers of people

   Hazardous, although not usually very toxic

   Disposal methods

    Open dumps

   Oldest method

   Common today in USA

   Usually now illegal and rarely used by large cities

     Sanitary Landfills

  Development of landfill

    Spread over suitable area - relatively flat or in excavation

    Compact with large machines

    Cover with about 1 foot of earth - layer is called a cell

    Repeat sequence => hill produced. Eventually closed

    Hill covered with about 2 feet of earth, vegetation planted

  Use for other purposes - sites for housing, business constructions, parking areas, sports

    Creative use: Mount Trashmore ski area

  Advantages of sanitary landfill

    Low initial cost

    Short start time

    Separation of waste material not necessary (cost)

    Completed sites usable for other purposes

  Disadvantages

    Lack of available locations, esp. in large cities

    Slow subsidence of landfill surface - problem for later buildings - common problem. Buyer beware!

    Leaking of hazardous materials

   Methane gas (from decomposition of paper and other organic materials) - flammable w. bad smell

   Other substances may contaminate groundwater

    Constant monitoring usually necessary - extra cost

    Future costs may be large - contamination, lawsuits

    Not suitable for toxic wastes

     Incineration

   Advantages

    Reduction of volume

    Energy generation

   Solid municipal waste: heat value = 1/2 good grade coal

   In Japan, much energy obtained; very little in USA

   Disadvantages

    Air pollution

   Smoke

   CO₂ - global warming

   Toxic organic vapors (unless very high temperatures)

    Must still dispose of unburnable wastes

     Composting

  Organic wastes spread out on ground to decompose

  Sewage, animal wastes, farming & vegetation wastes

  Micro-organisms (indigenous or introduced) partially decompose organic wastes

  Widely used in many European and Asian countries for farm wastes

  Advantages

    Resulting material is commercially valuable - high in plant nutrients

    Useful as fertilizers, soil conditioners - increase water retention of sandy soils

    Reduces waste product volume

  Disadvantages

    Must sort: remove glass, metals, non-compostables

    Crop residues - pesticide and herbicide contamination

    Municipal sewage - some hazardous substances

END

Water Pollution                Back to Top

Water Pollution

 When water is directly or indirectly modified by human activity so it is less suitable for purposes it could have served in its natural state.

l   Definition complex because subject is complex

l   Generally pollution results from human activity

Types of Water Pollution

 Water composition changed (compared to natural condition)

l   Hazardous pollutants - both to people and animals

    Organic (contains carbon)

   Dioxins, PCBs, benzene, etc.

    Inorganic - chiefly soluble forms of toxic metals

   Mercury, selenium, cadmium, etc.

l   Contaminants indirectly hazardous by changing ecology of site

    Organic

   Animal feedlot wastes

   increase algae in lakes

   indirectly leads to death of fish

   Inorganic

   Phosphates - increase algae in lakes

   Sulfates in rain - acid conditions in lakes

 Water temperature changed

l   Hot water from power plant cooling towers in lake

    May affect which organisms can live in the area

    May affect reproductive cycle of some organisms

Types of Sources

  Point Source

l    Well-defined source - single location

    Sewer outlet, steel mill discharge sites

    Some can be located easily but others difficult; factories hiding pollution

  Non-point Source

l    Source without readily identified location

    Numerous relatively small sources of pollution

    More difficult to deal with than point sources

    Agriculture-related pollution usually non-point source

Sources of Water Pollution

 Wide variety of sources

l   Leaking sanitary landfills

l   Chemical and other industries

l   Agriculture

l   Mining activities

l   Will emphasize agricultural (Iowa)

Agricultural Pollution

 Sediment pollution

l   > 3 billion tons of sediment supplied by erosion to waterways; 75% from agriculture

    Farming practices expose land surface to wind and water erosion

    Eroded sediments fill streams and small lakes

   Reduces capacity to carry or hold water

   Requires costly dredging

    Creates turbidity

   Decreases light -> affects underwater plants ->less food

Agricultural Chemicals

l   Types - pesticides/herbicides, fertilizers

    Soluble - leach into groundwater or pass into surface runoff

    Less soluble chemical often bonded to fine-grained sediment

   Carried by wind and runoff into surface water during erosion

l   Pesticides/herbicides

    Most are toxic to animal life

   DDT builds up in fatty tissues of animals

   Birds eat fish containing DDT

   Egg shells become calcium deficient; fragile and easily broken

l   Pesticides/herbicides

    Often hazards of pesticides/herbicides uncertain

   Farm family living where crops sprayed by airplane

   Dangerous

   Certainly chemicals spread beyond the targeted crop area

   Well-water contaminated by pesticides/herbicides

    Some persist for long times

    Decomposition products sometimes toxic

l   Fertilizers, including feedlots

    Contain organic matter and nutrients

   Phosphorous as phosphate

   Nitrogen as nitrate

   nutrients for aquatic plants as well as farm crops

   Create eutropic lakes - lakes with very abundant biologic activity, especially algae

   Early stage of eutrophication

   Lake may have increased fish and animal life

l   Fertilizers, including feed lots

    Phosphates/nitrates

   Later stage - algae/plants settle to lake floor

   Decay - use up oxygen

   Also produces methane and hydrogen sulfide in bottom sediments

   Advanced stage - bottom waters depleted in oxygen

   Fish die

   In Iowa, 100% of 107 lakes tested were eutropic as result of fertilizer/feedlot runoff

        Feedlot wastes

   Spills and leaks may contaminate groundwater

   Bacteria, nitrates

   Bad odor

   Effect on infants

   NO₃ in blood interferes with oxygen-carrying capacity of blood.

   Anemia (methemoglobinemia) may cause death

   >65 ppm in water very harmful to infants

   >45 ppm hazardous

   Safe level 10 ppm

BOD (Biological Oxygen Demand)

l   Measure of amount of oxygen required to break down organic matter

l   More organic matter -> higher BOD

l   Oxygen sag curve

    Plot of oxygen in stream water helps detect where organic material dumped into stream

Alleviation of Water Pollution

Stop further pollution

l   In time, environment will clean itself

    May take long time - years, decades, centuries,

    Harm may occur before natural cleaning is complete

l   Reduce existing pollution in groundwater and surface water

Groundwater Pollution

Reducing Groundwater Pollution

 Expensive

 Impossible if large-scale. Possible if relatively small and well-defined area of pollution

 Methods

l   Injection wells

    Inject chemicals down into polluted region

   Ex: Ba contamination; add sulfate, form BaSO₄

   Very insoluble

l   Injection wells

    Inject special microorganisms that feed on pollutant (bioremediation)

   Ex: for leaking underground storage tanks

    Inject oxygen

   Destroys organic pollutants by oxidation

l   Combined injection/withdrawal wells

    Two types of wells

   Injection well - inject water into contaminated area

   Withdrawal well - pump water from ground at nearby location

    Injected water flushes out polluted groundwater

    Contaminated water then cleaned above ground

    Prevents spread of contamination if started early

Surface Water Pollution

Reducing Surface Water Pollution

Methods

l   Dredging & removal of contaminated sediment

    After dredging, contaminated sediments cleaned, then replaced in lake or stream

   Much pollution in water becomes fixed to fine-grained sediments on stream/lake floors

   Hazardous chemicals slowly released from sediment into water

   Lake Laverne

l   Cleaning Water itself

    Difficult or impossible in large lakes and streams

    In smaller systems

   Method depends on type of contaminant

   Pesticides removed by passing contaminated water through carbon filters

   Other pollutants react with chemicals

   Acid lakes neutralized by adding powdered limestone CaCO₃: CO₃ ^2- + 2H⁺ => H₂CO₃

   Eutropic lakes - add calcium to precipitate calcium phosphate (insoluble)

Summary of Water Pollution

 Widespread in the USA and other countries

 Some serious problems but vast size of many water systems helps

l   Dilutes contaminants

l   But, low-level contaminants -> chronic exposure; health risks usually unknown

 Rate of pollutant addition to hydrosphere is large and growing

l   Eventually groundwater/surface water systems ability to dilute or destroy contamination will be overwhelmed

l   Then, perhaps, catastrophic situations

    abiotic oceans