Prior knowledge check• Have you ever

walked out into the ocean water? If so, do you know the name of the part of the Earth you walked on?

• What happens as you walk further out to sea?

• What does topography mean?

Topography

• A detailed map of the physical features of a region.

The Seafloor

• Objective:

• Describe the seafloor features.

Continental Shelf and Slope

• The continental shelf starts at the coastline and connects to the continental slope with a slight decline.

• The continental slope connects the shelf to the seafloor and is typically very steep. It is carved out by currents.

The Continental Shelf

• The pink region below is the shelf. It can extend out over 200 miles. Most ocean life lives here.

Abyssal Plains

• Seafloor areas that are relatively flat because they have been filled in with sediment.

• There is very little life in these areas.

Mid-Ocean Ridge

• An underwater mountain chain• This is where new ocean floor is made by seafloor

spreading• Remember that seafloor spreading happens at divergent

plate boundaries. The plate move apart allowing magma to seep up.

An Ocean Trench

• Convergent plates form ocean trenches.• One plate slides under the other.• Trenches are the deepest places on Earth• The Marianas Trench is ~ 7 miles deep• The Grand Canyon, in comparison, is only ~ 1 mile deep

Islands

Seamounts

Wrap-up

• How deep is the Mariana’s Trench?

• What kind of boundary is at an ocean trench?

• What is the underwater mountain range where seafloor spreading occurs called?

Seafloor Mining

• Petroleum, natural gas and placer deposits are mined from continental shelves.

• Manganese nodules are deep-water deposits that may be mined in the future.

petroleum

• An oily flammable liquid obtained from the ground that can be made into gasoline

Manganese

• A metallic chemical resembling iron but not magnetic

Wrap-up

• How are placer deposits formed?

• What is the name of an underwater mountain range?