Getting Geographic

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Earth’s continental landscapes—mountains, valleys, canyons—are familiar to students everywhere. But many students do not realize that ocean floor landscapes are equally dramatic and varied.

In the map to the right, which uses a technique called "choropleth mapping" to show depth, areas of darkest blue are the deepest parts of the oceans, while areas of light blue are relatively shallow.

Oceans cover approximately 71% of Earth’s surface. Their average depth is 16,000 feet (4,880 meters). But the ocean floor is marked by mountain chains called "mid-ocean ridges" and deep valleys called "trenches."

Mapping the Ocean Floor Landscape

Provide students with blank world maps.

Download a World Outline Map

Have students use National Geographic ocean floor maps to locate and label the following ocean floor features on their outline maps.

Features on the Ocean Floor

Pacific Ocean – Mariana Trench (-35, 827 ft/ -10,920 m.) Japan Trench (-34,318 ft/-10,375 m.); East Pacific Rise (under water ridge)

Atlantic Ocean – Puerto Rico Trench (-28,231 ft./-8,605 m.); Brazil Basin (-20,898 ft./-6,310 m.); Mid-Atlantic Ridge

Indian Ocean – Java Trench (-23,812 ft./-7,258 m.); Mid-Indian Ocean Ridge

Arctic Ocean – Fram Basin (-15,305 ft./-4,665 m.); Lomonosov Ridge

Extension Activity

In 2000, the International Hydrographic Organization identified a fifth division in Earth’s oceans—sometimes called the Southern Ocean. This ocean area, which extends from the shores of Antarctica to 60º South latitude, is not universally recognized as a separate ocean. Have students research the so-called Southern Ocean and identify its unique characteristics.