1. The Deep Oceans

2. Take-Away Points The earth has two kinds of crust
Continents have thick, light, granitic crust, Oceans have thin, dense, basaltic crust
How we probe the sea floor
Features on the sea floor and edges of continents are products of plate tectonics
Submarine landslides are important on continental margins
Deep ocean sediment comes from the continents and marine organisms

3. 1. The earth has two kinds of crust
The Two-Story Planet
1. The earth has two kinds of crust

4. Earth Has Two Kinds of Crust
2. Continents have thick, light, granitic crust, Oceans have thin, dense, basaltic crust

5. Continental and Oceanic Crust
Continental Crust (Granitic)
Residue of Long-Continued Partial Melting
Thick and Light
Ancient: > 2.5 b.y.
Oceanic Crust (Basaltic)
Derived Directly From Mantle
Thin and Dense
Young: < 200 m.y.
2. Continents have thick, light, granitic crust, Oceans have thin, dense, basaltic crust

6. Investigating the Sea Floor
Coring
Deep-Sea Drilling
Sonar
Seismic Refraction
Gravity Surveys
Magnetic Surveys
3. How we probe the sea floor

7. 3. How we probe the sea floor
Piston Coring
3. How we probe the sea floor

8. 3. How we probe the sea floor
Deep Ocean Drilling
Project Mohole
Original Intent: Drill to Earth’s Mantle
Drill in Oceans where Crust is Thinnest
Hidden Agenda: Complete History of Oceans
Challenge: Replacing Drill Bits in 5 km of Water
Plate Tectonics Showed that Mantle is Exposed in a Number of Places
3. How we probe the sea floor

9. 3. How we probe the sea floor
Deep Ocean Drilling
Original Objective Abandoned
Renamed Deep Sea Drilling Program
Now Called Ocean Drilling Program
3. How we probe the sea floor

10. 3. How we probe the sea floor
Sonar
3. How we probe the sea floor

11. 3. How we probe the sea floor
Seismic Refraction
3. How we probe the sea floor

12. Makeup of Ocean Crust
4. Features on the sea floor and edges of continents are products of plate tectonics

13. Anatomy of a Mid-Ocean Ridge

14. Continental Margins Shelf Slope Rise
Active: Subduction Zones. Sometimes Called Leading Edge
Passive: No Subduction. Sometimes Called Rifted or Trailing Edge
4. Features on the sea floor and edges of continents are products of plate tectonics

15. A Continental Margin
4. Features on the sea floor and edges of continents are products of plate tectonics

16. Evolution of a Passive Margin
4. Features on the sea floor and edges of continents are products of plate tectonics

17. Anatomy of a Passive Margin
4. Features on the sea floor and edges of continents are products of plate tectonics

18. Features of the Deep Ocean
Mid-Ocean Ridges
Abyssal Plains
Fracture Zones
Oceanic Trenches
Seamounts
Submarine Canyons
Submarine Fans
4. Features on the sea floor and edges of continents are products of plate tectonics

19. Crest of the Mid-Atlantic Ridge
4. Features on the sea floor and edges of continents are products of plate tectonics

20. Sea-Floor Spreading, Mid-Atlantic Ridge
Features on the sea floor and edges of continents are products of plate tectonics

21. Turbidity Flows – Grand Banks, 1929
5. Submarine landslides are important on continental margins

22. Where Sediment Comes From
6. Deep ocean sediment comes from the continents and marine organisms

23. Atlantic Sediments

24. 6. Deep ocean sediment comes from the continents and marine organisms
Deep Ocean Sediments
6. Deep ocean sediment comes from the continents and marine organisms

25. Take-Away Points The earth has two kinds of crust
Continents have thick, light, granitic crust, Oceans have thin, dense, basaltic crust
How we probe the sea floor
Features on the sea floor and edges of continents are products of plate tectonics
Submarine landslides are important on continental margins
Deep ocean sediment comes from the continents and marine organisms