The World’s Oceans and Their Features Part 1 Clinton Todd 10/19/05 Copyright 2005. Clinton Todd. All rights reserved.

What Do You Think? Is all land on Earth’s surface flat? What does the bottom of the ocean look like? If some parts of the ocean are deep, can we still tell what they look like?

The Oceans About 71% of the Earth’s surface is covered by ocean

The Oceans The oceans are divided into four main basins Pacific Atlantic Indian Arctic The largest ocean and deepest at 3940 Half the size of the Pacific and more narrow Slightly smaller than the Atlantic but with the same depth Only about 7% the size of the Pacific and ¼ as deep as the rest

The Ocean Floor The topography of the ocean’s floor is just as varied as that of the land area Note the relief on the following map…

The Ocean Floor http://www.staff.amu.edu.pl/~zbzw/glob/seafloor.jpg

Studying the Seafloor Sonar, developed in the 1920’s transmits sound waves to the ocean floor and plots points on the ocean floor based on the length of time it takes the waves to be reflected back. Sonar is an acronym for SOund NAvigation and Ranging

Studying the Seafloor Satellites measure sea surface height using the same principle as sonar, except they use radio waves (RADAR), instead of sound Submersibles small crafts that may be manned or unmanned that use various sensors and instruments to explore the ocean at depth.

Ocean Floor Features There are three major regions of topography that divide the ocean floor They are the continental margins, the ocean basin floor, and the mid ocean ridge

Continental Margins The area in which continent and ocean floor begin to merge is called the continental margin The three parts of the continental margin are called the continental shelf, continental slope, and continental rise

Continental Margins http://www.utdallas.edu/~pujana/oceans/image017.gif

Continental Margins The continental shelf is a gently sloping, shallow area of the ocean floor that extends outward from the edge of a continent   They contain important mineral, oil and natural gas deposits     

Continental Margins The continental slope is a rather steep incline leading down from the seaward edge of the continent shelf Deep valley called submarine canyons are cut into the slope. These canyons were probably eroded by dense, muddy turbidity currents created by some disturbance, like an earthquake

Continental Margins The continental rise is on the seaward side of the slope and has a much smaller incline There are no canyons in this region

Ocean Basin Floor The ocean basin floor is between the continental margin and mid-ocean ridge The region includes deep ocean trenches, abyssal plains, and seamounts and guyots

Ocean Basin Floor Deep-ocean trenches are long and narrow creases that are the deepest parts of the ocean They form at sites where a moving tectonic plate descends beneath another and goes back into the mantle The Mariana Trench is the deepest place on Earth at 11022 m below sea level!

Ocean Basin Floor Abyssal plains are extremely deep and flat The sediments of the plains come from either turbidity currents that have carried them or from the settling of suspended sediments

Ocean Basin Floor Seamounts are submerged volcano peaks After reaching the water’s surface the volcanoes form islands like the Hawaiian chain Over millions of years these islands may subside back into the water, where they are then referred to as guyots

Mid-Ocean Ridges Mid-ocean ridges are found near the center of an ocean basin They are a system of underwater mountains and sites of oceanic crust development These are places were oceanic plates are diverging and new magma rises from the center

Mid-Ocean Ridges

Resources: Ford, Brent A., Project Earth Science:  Geology. Arlington:  National Science Teachers Association, 1996. Tarbuck, Edward J. and Frederick K. Lutgens. North Carolina Environmental/Earth Science. Prentice Hall. New Jersey. 2006. “Mid-Ocean Ridge Spreading.” Windows to the Universe. Jan 5 1998. Oct 16 2005. http://www.windows.ucar.edu/tour/link=/earth/interior/mid_ocean_ridge.html&edu=elem

The World’s Oceans and Their Features Part 2 QUICK QUIZ

Instructions Navigate through the presentation and answer the questions accordingly on a separate sheet of paper The numbers for each question are located in the title bar Note: The picture used for number one may be helpful when answering other questions!

1.) Label the letter in the diagram with the corresponding feature.

2.) New seafloor is formed at mid-ocean ridges as plates Converge Diverge Collide Sink

3.) The oceans make up what percentage of the Earth’s surface? 50 29 93 71

4.) The ______ is a gently sloping, shallow area of the ocean floor that extends outward from the edge of a continent Guyot Continental slope Continental shelf Abyssal plain

5. )Click the link provided and view the animation 5.)Click the link provided and view the animation. Where does the crust (in yellow) go after being pushed away at the mid-ocean ridge? http://www.windows.ucar.edu/tour/link=/earth/interior/mid_ocean_ridge.html&edu=elem

6.) Briefly explain different methods by which scientists may map the seafloor.