1. The Water Planet
The oceans cover 71% of the planet and regulate its climate and atmosphere 1

2. The Geography of the Ocean Basins
There are four ocean basins
Pacific – the deepest and largest
Atlantic
Indian
Arctic – smallest and shallowest 2

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4. The Geography of the Ocean Basins
Connected to the main ocean basins are shallow seas
e.g. Mediterranean Sea, Gulf of Mexico, South China Sea
They all connect to form a world ocean where seawater, materials, and organisms can move about 4

5. The Structure of the Earth5

6. Internal Structure
In the early molten Earth, lighter materials floated toward the surface
They cooled to form the crust
The atmosphere and oceans then formed
Earth is the right distance from the sun for liquid water, and life, to exist 6

8. The dense core is mostly iron Solid inner core and liquid outer core
The swirling motions produce the Earth’s magnetic field 8

9. The mantle is outside the core and under the crust
Near molten rock slowly flows like a liquid
The crust is the outer layer, comparatively thin
Like a skin floating on the mantle 9

10. Continental and Oceanic Crusts
There are differences in the crust that make up sea floors and continents 10

11. Ocean crust Made of basalt – a dark mineral More dense Thinner
Younger rock; 200 mil years 11

12. Continental crust Made of granite – lighter color Less dense Thicker
Older rock; 3.8 bil years 12

13. That’s why ocean crust is covered by water
So continental crust floats high on the mantle and ocean crust floats lower
That’s why ocean crust is covered by water 13

14. Asthenosphere
The plates float on a fluid layer of the upper mantle called the asthenosphere.
At mid-ocean ridges the plates move apart
If the plate has continental crust it carries the continent with it
Spread 2-18 cm/year
This explains continental drift

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16. The plates colliding can be ocean ->continent
♦ Ocean plates always sinks below
♦ Produces earthquakes and volcanic mountain
ranges; e.g. Sierra Nevada

17. The plates colliding can be cont -> cont
♦ Neither plate sinks, instead they buckle
♦ Producing huge mountain ranges; e.g. Himalayas

18. The plates colliding can be ocean -> ocean
♦ Earthquakes and volcanic island arcs; e.g. Aleutian
Islands

19. The Origin and Structure of the Ocean Basins
The Earth is a world of constant transformation, where even the continents move 19

20. Early Evidence of Continental Drift
400 years ago Sir Francis Bacon noted the continental coasts of the Atlantic fit together like pieces of a puzzle
Later suggested the Americas might have been once joined to Europe and Africa
Geologic formations and fossils matched from opposing sides 20

22. Early Evidence of Continental Drift
Alfred Wegner gave hypothesis of Continental Drift in 1912
Suggested that all the continents had once been a supercontinent, named Pangea
Started breaking up ~180 mil years ago

23. The Theory of Continental Drift could not explain how the continents moved
The Theory of Plate Tectonics explains it all Continents do drift slowly around the world 23

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25. Bathymetry
Measures the vertical distance from the ocean surface to mountains, valleys, plains, and other sea floor features
© 2011 Pearson Education, Inc.

26. Bathymetry Overview
The study of bathymetry charts ocean depths and ocean floor topography. Echo sounding and satellites are efficient bathymetric tools. Most ocean floor features are generated by plate tectonic processes.
© 2011 Pearson Education, Inc.

27. Discovery of the Mid-Ocean Ridge
After WWII sonar allowed detailed maps of the sea floor. They discovered the mid-ocean ridge system
A chain of submarine volcanic mountains that encircle the globe, like seams on a baseball 27

28. Mid-Ocean Ridge The largest geological feature on Earth
Some of the mountains rise above sea level to form islands, e.g. Iceland
The mid-Atlantic ridge runs down the center of the Atlantic Ocean and follows the curve of the opposing coastlines
Sonar also discovered deep trenches

30. Significance of the Mid-Ocean Ridge
Why are they there? How were they formed?
Lots of seismic and volcanic activity around
the ridges and trenches
Rock near the ridge is young and gets older
moving away from the ridge
There is little sediment near the ridge, but it
gets thicker moving away 30

31. Creation of the Sea Floor
Huge pieces of oceanic crust are separating at the mid-ocean ridges
Creating cracks called rifts

32. Image: A diver swims between the Eurasian and North American plates in Thingvellir lake, Thingvellir National Park, Iceland. Iceland is one place where a mid-ocean ridge can be seen on land and in shallow waters.(credit: Wild Wonders of Europe/Lundgre)

34. Magma from the mantle rises through the rift forming the ridge
The sea floor moves away from the ridge
This continuous process is called sea-floor spreading
New sea floor is created

35. This explains why rocks are older and sediment is thicker as you move away from the ridge
This also explains the magnetic stripes found in the sea floor

38. The Mid-Ocean Ridge and Hydrothermal Vents
At the center of the ridge, where the plates pull apart, is a central rift valley
Water seeps down through cracks, gets heated by the mantle, then emerges through hydrothermal vents 350oC (660oF) 38

39. Dissolved minerals from the mantle, like sulfides, are brought up
Black smokers form when minerals solidify around a vent
Marine life, including chemosynthesizers, exist around hydrothermal vents

40. END

41. The Geological Provinces of the Ocean
Two main regions of the sea floor
Continental margins – the submerged edge of the continents
Deep-sea floor 41

42. Continental Margins Boundaries between the continental and ocean crust
Consists of shelf, slope and rise 42

43. The Continental Shelf The shallowest part
Only 8% of the sea floor, but biologically rich and diverse
Large submarine canyons can be found here
Ends at the shelf break, where it steeply slopes down 43

44. The Continental Slope The edge of the continent
Slopes down from the shelf break to the deep- sea floor 44

45. The Continental Rise
Sediment accumulates on the sea floor at the base of the slope 45

46. Deep-Ocean Basins
10,000-16,000 ft
Abyssal plain - flat region of the sea floor
Seamounts – submarine volcanoes
Guyots – flat-topped seamounts
Both were once islands, but now covered with water
Trenches – the deepest part of the ocean 46

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