1. INTRODUCTION What is at the Sea floor?
Continental margins and ocean floors
Sediments

2. CONTINENTAL MARGINS Continental Shelf Continental Rise Shelf Break
EARTH: An Introduction to Physical Geology 7th ed / Tarbuck & Lutgens fig 18.4
Continental Shelf
Shelf Break
Continental Slope
Continental Rise
Submarine Canyons

3. CONTINENTAL MARGINS
Thurman Essentials of Oceanography 6/e

4. CONTINENTAL SHELVES Found at margins of continents Flat
Average km in width
Formed by erosion and transport or dams
Ends at change in slope (Shelf break)

5. CONTINENTAL SLOPE Extends from shelf break to rise
Submarine canyons are major features
Submarine canyons formed by:
River erosion
Turbidity currents

6. SUBMARINE CANYONS

7. GRADED BEDS
Each layer grades from coarse at its base to fine at the top.
EARTH: An Introduction to Physical Geology 7th ed / Tarbuck & Lutgens fig 6.21

8. CONTINENTAL RISE Located at base of slope
Located where have a change of slope

9. THE OCEAN BASIN FLOOR

10. THE OCEAN BASIN FLOOR http://ibis.grdl.noaa.gov/cgi-bin/bathy/bathD.pl
Smith & Sandwell (1997) global ocean bathymetry map, the most complete, high-resolution image of sea floor topography currently available.

11. THE OCEAN BASIN FLOOR
Covers 30% of earth’s surface, continents cover 29% of surface
Begins at base of continental rise
Known as the abyssal plain
Sedimentation: Passive and turbidity currents

12. FEATURES OF THE SEA FLOOR
Seamounts
Guyots
Ridges and rises
Trenches

13. SEAMOUNTS & GUYOTS
Thurman Essentials of Oceanography 6/e

14. NEAR-RIDGE SEAMOUNTS Many originate near mid-ocean ridges
Are especially common near fast spreading ridge segments
Preferentially located near bends or offsets in the ridge crest.

15. Taney Seamounts perspective view from the south-southeast

16. RIDGES AND RISES South West Indian Ridge
South West Indian Ridge

17. RIDGES AND RISES Underwater volcanic mountain chain
extends for 65,000 km
1000 km wide
m high
Ridges = steep slopes; Rises = gentle slopes
Contain central rift valley
15-50 km wide
m deep
Offset by fractures

18. THE MID-ATLANTIC RIDGE
Thurman Essentials of Oceanography 6/e
Figure A is a cross-sectional view of the fast-spreading Mid-Atlantic Ridge. Figure B is a cross-sectional view of the fast-spreading East Pacific Rise. On both cross sections, vertical exaggeration is 50 times normal. After Schmidt, V. A Planet Earth and the New Geoscience (Fig. V4), DuBuque, Iowa: Kendall/Hunt.

19. TRENCHES
EARTH: An Introduction to Physical Geology 7th ed / Tarbuck & Lutgens
Distribution of the world's oceanic trenches, ridge system, fracture zones, and transform faults. Where transform faults offset ridge segments, they permit the ridge to change direction (curve) as can be seen in the Atlantic Ocean.

20. TRENCHES Occur along some continents
Mariana trench the deepest (11,020 m)
Peru-Chile trench the longest ( 5900 km)

21. EARTH: An Introduction to Physical Geology 7th ed / Tarbuck & Lutgens