1. The Sea Floor

2. A: Right! The Southern Hemisphere contains nearly 80% water by volume.
Brain Warmers:
Q: Of the Norhern and Southern Hemisphere, which one contains the most water??
A: Right! The Southern Hemisphere contains nearly 80% water by volume.
Q: Which ocean is the largest? The deepest?
a. Arctic b. Pacific c. Atlantic d. Indian
A: Pacific
A: Pacific again!

3. Figure 2.02

5. How did it all get this way?
Big bang leftovers!
Density played a major role.
How’s that work??
Density = mass/volume
Lighter stuff stays on the top!

6. Figure 2.03

7. Ocean Floor Facts
Ocean crust is composed of basalt. Basalt is common to the sea floor also.
Much of the crust which forms land masses is composed of granite.
Much of the ocean floor and crust differs in age too! (200 myo compared to 3.8 byo!!)
Why??

8. Ocean Floor Structure
Sir Francis Bacon (1620) considered contents puzzle pieces.
Geological features (coal deposits) matched on opposite coasts.

9. Ocean Floor Structure
Sir Francis Bacon (1620) considered contents puzzle pieces.
Geological features (coal deposits) matched on opposite coasts.
Alfred Wegner (1912) hypothesized continental drift.

10. 180 mya
Pangea Bound…
Continents may have been one piece which later broke apart, moved, and formed present day conditions.
How??
Plate tectonics ocean floor movement.
Consists of faults (cracks) which form the mid ocean ridges (mountains).
150 mya
95 mya
45 mya
15 mya

11. Current Mid-ocean ridges & trenches
Figure 2.05
Current Mid-ocean ridges & trenches

12. These locations are a significant source of geological activity!
Figure 2.06
These locations are a significant source of geological activity!

13. Figure 2.07

14. Magnetic anomalies occur here too!
Figure 2.08
Sea floor spreading occurs at
mid-ocean ridges.
Magnetic anomalies occur here too!

15. Sea-floor spreading
where the ocean floor
moves away from
the mid-ocean ridge
records the magnetic
fields of the earth.

16. Locations and direction of seafloor spreading.
Figure 2.10
Locations and direction of seafloor spreading.

17. Crust and mantle come together to form the lithosphere.
Figure 2.11
Crust and mantle come together to form the lithosphere.
Subduction and resulting subduction zones where ocean floor
plates flow beneath the mantle of the crust are places of tectonic activity.

18. Trenches and island arcs can be formed when two sections of ocean
Figure 2.12
Trenches and island arcs can be formed when two sections of ocean
plates come together.

19. Some areas can be quite acitve!!
Figure 2.13
Mt. Veniaminof, Alaska
Some areas can be quite acitve!!

20. Shear (transform) boundary.
Figure 2.14
When plates move
sideways then a new
formation called a
Shear (transform) boundary.
San Andreas Fault, CA

21. Figure 2.15
Swirlling vs. Pulling
Convection suggests that continents move on a “soup” of rock,
Whereas slab pulling indicates that as rock cools, it sink beneath
the surface and “pulls” lithosphere into the depths (This is the
currently accepted explanation.)

22. CONTINENTAL MARGIN (boundary between oceanic crust & continental crust)
Continental Shelf – shallow, flat, most life
Shelf Break - shelf abruptly deepens
Continental Slope - edge of continent
Continental Rise - sediment build up at slope base

23. Figure 2.20

24. Figure 2.21

25. Figure 2.22

26. ABYSSAL PLAIN (DEEP SEA FLOOR)
10,000 – 16, 500 ft deep

27. Generally flat except for: Seamounts – submarine volcanoes

28. Text Art 2.02

29. Guyots – flat-topped seamounts (inactive)

30. Heated water emerges through rift cracks Water 68F – 660F
HYDROTHERMAL VENTS (DEEP SEA HOT SPRINGS)
Found in mid-ocean ridge depression called “Central Rift Valley”
Heated water emerges through rift cracks Water 68F – 660F
Water dissolves toxic minerals (sulfides) which solidify

31. Black Smoker

33. The first organisms to populate the vents are bacteria, then other microorganisms, including amphipods and copepods appear.
These are followed by limpets (snails), shrimp, crabs, tube worms, fish, and octopi. Sometime later acorn worms, dandelion-like animals, and other species of shrimp and tube worms add to the expanding community. In their most advanced stages vents are home to mussels, a variety of worms, anemones, and a large population of crabs, as well as many of the earlier colonists.