1. The Ocean EARTH: The only planet w/ Oceans (or liquid water)
Covers 71% of earth’s surface
“Divided” into 4 large basins
Pacific (largest, deepest)
Atlantic
Indian
Arctic (smallest, shallowest)
A fifth? The Antarctic…

2. Ocean basins
South pole view

3. Ocean Basin Depths

4. Interior of Earth

5. The Difference Between an Ocean and a Continent…ROCKS!
Continent: very thick, very old, less dense and made up of Granite
Ocean (floor): younger, more dense, not as thick and made up of Basalt
Thus, the “Ocean Floor” “sinks” below the continent(s) and provides the habitats of marine organisms

7. Continental Drift
If we know the Continental Crust and Oceanic Crust have different densities…how did they “separate” to become 7 continents and 4 oceans?
We start (Pangea) 210 mya!

8. PANGEA (the super continent)
180 million yrs. ago – all continents were attached together and have slowly moved apart over time
Discovered (S. F. Bacon, 1600’s) “Coasts of continents fit together like a puzzle.”
Lead to theory of continental drift and plate techtonics.

9. Pangea (reptile fossils)

10. So…WHERE DID WE START AND WHERE ARE WE NOW?

11. Figure 2.14a

12. Figure 2.14e

13. PLATE TECTONICS
Continental drift leads to the theory of Plate tectonics
Although Bacon discussed it in the 1600’s, it was not understood until the 1960’s.

14. The Ocean Floor (P. Tectonics)
Mid-Ocean Ridges
Underwater mountain ranges
Fault: Crack in earths crust
Rift: Ocean crust separates & creates “cracks”
Earthquakes are common
Trenches
Deep depressions in the seafloor
Mostly in Pacific, Volcanoes common

15. Major features of Sea Floor

16. CO 2
Mid-Atlantic Ridge (above sea surface in Iceland)

17. Sea-Floor Spreading (plate tectonics)
New sea-floor forms at mid-ocean ridges (where the edge of these “plates” meet)
Continental Drift: If the plate (as it spreads away from the ridge) contains continental crust (on top) the continents “drift” (move) apart.

18. How? Convection and Density!

19. Figure 2.08 Sea Floor Spreading: X-section of sea floor @
Mid ocean ridge

20. Figure 2.07 Paleomagnetism: Normal magnetism @ ridge crests (but
Reversed in other
locations)

21. We get: Plate boundaries
With geologic activity, such as earthquakes, that (may) correspond w/ these plate boundaries

22. Earthquake and Volcano distribution

23. Lithospheric plate boundaries

24. How does everything move? Plate Tectonics!
The earth’s upper layer, the lithosphere, is divided into plates
Plates may contain sea-floor, continents, or both
Plates are moving (few cm per year), floating on top of the earth’s molten mantle

25. Subduction (plate techtonics)
sea-floor is destroyed by plunging back into the earth’s interior at trenches
When 2 plates collide, 1 dips below the other (in to the mantle) and 1 is destroyed (causing, sometimes, earthquakes)
Ocean vs. Cont. plate: ocean plate destroyed, can get coastal mountain ranges
Ocean vs. Ocean plate: 1 dips = volcano or earthquake
Cont. vs. cont: none destroyed, mnt. Ranges fold
2 plates, no collision, lock/shear/earthquake (S. Andreas F)

26. Figure 2.10
Continental + Oceanic plate collision = trench, earthquake

27. Figure 2.11
2 oceanic plates collide = trench/earthquake

29. San
Andreas
Fault
(CA)
Figure 2.13

30. Sea Floor Regions
All of this “plate” movement and geologic activity that occurs under the water yields different sea floor regions
Each dependent upon depth, width, slope etc.

31. Regions of the sea-floor
Continental Margins contain continental shelf, slope and rise
Cont. shelf = shallow, most “rich” (diverse)
Deep Ocean Floor, “Abyssal Plain”
The Ocean “floor” (on average) is miles BELOW the oceans (water) surface!

32. Figure 2.17
Continental margin

33. Active vs. Passive Margins
An active margin
is a geologically
very “active” area;
whereas a
Passive margin is a
geologically
in-active
area.

34. (Passive Margin) Continental Shelf (19 mi. off of Atlantic City, NJ)
Figure 2.18
Tom’s Canyon
Shelf break

35. The California Coast
Monterey
Canyon

36. Active Coast (CA)

37. Margins
We know what it looks like at the top of the (Continental) margin but what does it look like AT the margin (at the ridge line, deep under the oceans surface)?

38. “Black
Smoker”
Hydro-
thermal
Vent
(at a
Mid
Ocean
Ridge)
Figure 2.24

39. Black Smoker, cross section

40. Who are we? Iceland, Azores = fault (mountain)
Andes (mts.) = subduction trench (o-c)
Aleutian/Mariana (Is.) = sub. trench (o-o)
Himalayas (mts.) = sub. Trench (c-c)
Hydrothermal vents: Deep Ocean
See Fig. 2.5 for locations and other “interesting” places to visit.

41. Major features of Sea Floor