This is a text version of the notes presented in class.  Some figures of interest in your textbook are indicated here, as well.

Feel free to email the instructor (alisonjs@kent.edu) with any
comments about the format and ease of use of these online notes.

First- A Little Review from Tuesday-- Latitude, Longitude, Maps

Example Map Projection: Mercator
The Mercator projection is frequently used by mariners
Mercator projections distort distance and area near the poles
Graphic: Garrison, App. IV, Fig. 2, pg 471.

 Example Map Projection: Equal Area
Equal area projections retain relative sizes of land masses
Linear paths between points are distorted (particularly near the edges of the map)
 

 Latitude and Longitude
Latitude: North-South,  Range=90°N to 90°S, North Pole=90°N, South Pole=90°S
Longitude: East-West, Range=0°E-360°E or or 180°W-180°E, 0°=Greenwich England
Latitude and longitude uniquely specify the location of each place on Earth
Kent, Ohio=41.15°N, 278.64°E
Graphic: see Garrison, App. III, Fig. 4

The Ocean Floor
In this lecture, we will cover information about the following aspects of the ocean floor:

I.  Distinctive features of the ocean floor
• Continental shelves, slopes and rises
• Abyssal plains
• Mid-ocean ridge
• Trenches
• Guyots and Seamounts

and

II.Sediments on the ocean floor
• Terrigenous – Terrestrial sources
• Biogenic- Biological sources
• Authigenic-Precipitated out of the water
• Cosmogenic-dust and debris from space

I.  The Ocean Floor
1.  Ocean basins - large expanses of open ocean
Marginal seas - smaller saltwater regions connected to ocean basins by narrow passages
There are many marginal seas (e.g., Mediterranean, Norwegian, Caribbean)

Graphic-Look at Garrison, Fig 1.2, pg. 3, see App. IV, Fig. 4 for a more detailed view.
 

2.  Bathymetry - Measuring Ocean Depths
Bathymetry can be measured using:
- weighted lines
- sound (acoustics)
- Earth-orbiting satellites (new!)
Acoustic bathymetry:
- a sound pulse is sent to the seafloor
- measure time needed for the echo to be received
- this time is related to the distance to the seafloor
Graphic: After Garrison, Fig. 4.2, pg 100

3. Features of an Ocean Basin
 continental margins:  shelves, slopes, rises
 abyssal plains
 mid ocean ridges
 trenches
 submarine canyons and deep sea fans
 guyots and seamounts

Look at Graphic: Garrison, Fig. 4.22, pg 115

4. Parts of a Continental Margin
Shelf - submerged area adjacent to continent
Slope - transition between continental shelf and deep sea floor
Rise - area at the base of the continental shelf covered by sediment deposited from the shelf
Graphic: Garrison, Fig. 4.11, pg 108

5. Continental Shelves
- Seaward extension of continental material
- Contain much of the sea's mineral and oil deposits and home to most economically important sea life
 
In general, continental shelves are more biologically active than ocean basins

6. A Real Continental Margin
Continental margins are not the same everywhere:
  - shelf width varies from place to place
  - slope angle varies from place to place
  - large-features are found on some margins

7. Submarine Canyons and Deep Sea Fans
Submarine canyons cut through the continental shelf and slope
- Carved by catastrophic events (turbidity currents) that carry sediment from the continental slope to
the deep sea and deposits it in a deep sea fan
Graphic: Garrison, Fig. 4.16, pg 111

8. Mid-Ocean Ridges
- Submerged mountain chains circle the Earth
- Most rise about 2 kilometers above the ocean floor
- Seismically active regions (sites of many earthquakes)
Graphic: Garrison, Fig. 4.21, pg 114

9. Abyssal Plains
Are expansive, flat areas of the deep oceans
These are some of the flattest features on the planet
Graphic: Garrison, Fig. 4.22, pg 115

10. Ocean Trenches
Are 3-6 km deeper than surrounding ocean
Geologically active (sites of  very large earthquakes and tsunami)
Graphics: Garrison, Fig. 4.30, pg 122, and Garrison, Fig. 4.31, pg 123.

11.  Guyots and Seamounts
Guyots – flat topped, submerged, inactive volcanos
Seamounts – isolated volcanic peaks that rise at least 1,000 feet above the sea floor

For a good figure showing Global Seafloor Topography
See Graphic: See Garrison, Fig. 4.32, pgs 124-125.

II.  Sediments on the sea floor:  Different kinds of sediment are found in different parts of the ocean.  These types can be grouped into
 Terrigenous-sediment coming from the continents & islands
 Biogenic-organically produced material, like shell material, made by organisms
 Authigenic-minerals precipitating out of the water column and settling out
 Cosmogenic-dust and small particles, like tektites, reaching Earth from space

1. Terrigenous Sediments
Origin = continents and islands
- erosion of land
- volcanic ash
- wind-blown dust
Transport = rivers and wind

2. Biogenic Sediments
Origin = biology (shells and skeletons of marine organisms)
- abundant where biological productivity is high
- organic molecules in these materials can form oil and natural gas deposits

3. Authigenic and Cosmogenic Sediments
Authigenic - dissolved minerals present  in seawater chemically react to form solids
Example:  Manganese nodules
Cosmogenic - material from outer space
Example: Interplanetary dust
Authigenic and cosmogenic sediments are rare

4. Influence of Water Depth on Sedimentation
Shallow continental margins are terrigenous
Mid-depth waters far from coasts are biogenic
Deep ocean basins have red clays and authigenic nodules
- Calcium-based biogenic sediments dissolve in the deep ocean, leaving the small terrigenous
  clay particles that have traveled far from land
Graphic: Garrison, Fig. 5.15, p. 141

5. Sediment Thickness
Thick sediments near continental shelves - terrigenous and biogenic input
Thin sediments in deep regions - little terrigenous input, little biogenic accumulation
Very thin sediments near mid-ocean ridges - young seafloor

6. Global Distribution of Sedimentary Deposits
See Garrison, Fig 5.10, pg 137.
 

8. Preview of Next Lecture – Plate Tectonics & the Dynamic Earth
Readings:  Chapter 3, pgs 59-69
Focus Question:  What is the significance of ocean trenches and mid-ocean ridges?