1. Topography of the Ocean
H.M.S. Challenger

2. Topography refers to the shapes of the ocean floor.
In this session you will learn the different surface features of the ocean floor along with their names.
Describe the various physiological features associated with the ocean basins.
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3. Earth Beneath the Sea
The H.M.S. Challenger was one of the first ships to do extensive oceanic studies.
The echo sounder was an innovation that allowed for a lot of research to be able to be conducted about the ocean's floor.
Here is a problem:
Sound travels 5000 ft. per second through water.
It takes one second for the echo to go from the ship and then be bounced off the bottom and return to the ship.
The total distance is 5000 feet, so you know from the ship to the ocean floor it is half of that, or 2500 feet.
The formula 1/2(5000)(time traveled) can be used anytime.

4. The Earth’s crust can be divided into two parts:
Continental crust
Oceanic crust
Ocean basins can be divided into two regions:
continental margins
deep ocean basins

5. Continental Margin which is made up of:
Continental Slope
Continental Rise
Continental Shelf
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6. Features of the Deep Ocean Basin
Abyssal Plains
Ridges
Seamounts and Guyots
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8. Vocabulary
Continental Margin – the part of our continent that extends into the ocean.
Continental shelf – a slow drop in the ocean floor beginning at the coast line.
Continental Slope – starting at the outer edge of the continental shelf the continental slope drops off steeply toward the ocean floor.
Continental Rise – the area of the ocean floor that extends between the continental slope and the deep ocean floor.
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9. Continental Margins
Made up of three distinct regions, the Continental Shelf, Continental Slope, and Continental Rise.
Mostly made up of sediments that have been washed off of land.
Considered to be part of each continent’s land mass.
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10. Continental Shelf
A gently sloping surface (less than one tenth of a degree) that begins at the shore line and extends to the beginning of the Continental Slope.

11. Continental Shelf (continued)
It is primarily made up of sediments that have been carried down rivers.
Numerous hills, terraces, canyons
The width of the Continental Shelf varies. Scientists claim the average width is about 65 km.
Submerged part of the continent
Locally cut by canyons formed by currents and moving sediment

12. Submarine Canyons and Turbidity Currents
Submarine canyons, steep walled underwater valleys, are created by turbidity currents. Click on the links to learn more about them.

13. Continental Slope
A fairly steep drop that separates the Continental Shelf from the Continental Rise.
Between the shelf and the floor and deep ocean
Boundary between continental and oceanic crust
Slopes an average of 2-3 degrees
50 degrees off volcanic islands (much steeper!)
It is made up of the same sediments as the Continental Shelf.

14. Continental Rise Less steep than Continental Slopes.
Made of sediment deposited at the boundary between the continental slope and the abyssal plain.
The width of the Continental Rise ranges from a few kilometers to hundreds of kilometers.

15. The Ocean Basin Floor
30% of the Earth's surface are made up by these landforms:
Deep ocean trenches, where 2 converging plates meet, are the deepest regions of Earth. The Marianas trench can reach up to 36,000 ft. deep.
Abyssal plains are very flat regions made of the sediment carried by turbidity currents.
Seamounts are isolated volcanic peaks made by hotspots, like Hawaii. Others are near ocean ridges. Others emerge as land, like St. Helena.

16. A Deep Ocean Trench

17. Abyssal Plain Depth may be 3,000–6,000 m or more
Flat, deep ocean floor.
Depth may be 3,000–6,000 m or more
Thick accumulations of sediment

18. The Topography of an Abyssal Plain

19. Location of some Seamounts around the globe

20. Vocabulary (continued)
Ridges – the ocean floor has ocean basins in it. Each basin has mountain ranges just like the mountain ranges on land. Underwater mountain ranges form ridges that look like long peaks.
Seamounts – volcanic mountains that rise more than 1,000 meters above the ocean floor. Hawaii is a seamount.
Guyots – volcanic mountains that have been flattened by wave action and now are totally underwater.
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21. Mid Ocean Ridges
This is where sea floor spreading occurs, and new crust is formed.
These regions make up to 20% of the Earth's surface
They run a course of 40,000 miles around the Earth that looks like a baseball seam.
Click here to learn about the Mid-Atlantic Ridge (below, the MAR is on land in Iceland)

22. Island of Surtsey emerged near Iceland, 425 feet below the ocean
Undersea Volcanoes
Thick, black smoke billowed miles into the sky
Scorching, red lava oozed from a turbulent sea
Molten lava hardened into pumice and cinder
Island of Surtsey emerged near
Iceland, 425 feet below the ocean

24. Seamounts
Seamounts and Guyots are both individual volcanic mountains on the ocean floor
Distinct because seamounts tend to be circular or conical
The difference between seamounts and guyots  Guyots have been flattened and are below the ocean surface.
Some seamounts do not reach the ocean surface either.

25. Guyot
Flat-topped seamount rising from ocean floor like a volcano but planed off on top and covered by appreciable water depth.

26. Guyot Formation

27. Coral Reefs and Atolls
Coral reefs are made of skeletal remains from coral polyps and algaes.
They live in warm waters, above 75 degrees F anually.
The H.M.S. Beagle expedition did research on atolls and their locations.
Atolls are islands made out of coral.

28. Atolls
A coral reef that formed around an undersea volcano which has since been eroded by wind and waves.

29. Resources
Plate Tectonics