Underwater Mountains & Trenches

Underwater Mountains & Trenches lesson plan

When you look out on the ocean, what do you see? Underneath those cool blue waves are mountains and canyons, just like on the Earth’s dry surface!

  • 1.

    Where is the Earth’s deepest trench? The Grand Canyon? Or the Copper Canyon? It’s under the sea. The Marianas Trench near Guam in the Western Pacific Ocean plummets almost 7 miles (11,033 m) below the sea. An amazing number of geographic features lie under the oceans’ surface. These underwater features were formed in much the same way as the Earth’s features above water.

  • 2.

    Mountain ranges are common in the world’s oceans. The Mid-Ocean Ridge is the largest single feature on Earth, covering nearly 40,000 miles (64,000 km) in the middle of the Atlantic. Mauna Kea, in Hawaii, rises the highest from the ocean floor. Isolated mountains under the sea are called seamounts. Some, called guyots, are extinct volcanoes with flat tops. Perhaps at one time these were islands whose tops were worn away by ocean currents and waves.

  • 3.

    A color-key map is one way to show what you are learning about the ocean’s geography. On paper, outline the Earth’s continents, major ocean mountains, and primary trenches with Crayola® Erasable Colored Pencils. Check each other’s accuracy. Erase to make any corrections.

  • 4.

    Fill in the continents with Crayola Markers. Mark locations of major ocean mountains in one color. Draw trenches in a different color. Add your color key to the map.

  • 5.

    On the back of your map, squeeze a thick line of Crayola School Glue along the mountain ridges. Air-dry. Press on the paper from the front. Apply another layer of glue if the ridges do not stand out.

  • 6.

    With Crayola Scissors, cut away inside the trench outlines. Glue a contrasting color of paper to the back of the map. Air-dry the glue.

  • 7.

    Label your map’s primary features. Compare your findings with other students’ maps. What different geographic features did you identify?


  • • Students identify the oceans’ geographic features. </P>
  • • Students locate significant oceanic features around the globe. </P>
  • • Students reproduce their findings using a relief map format. </P>


  • • Explore the technology that makes underwater information available to scientists. Chart how this technology developed over time from the earliest pods to the latest sonar instruments. </P>
  • • Study the different ages of Earth’s features. For example, the rock of the ocean mountains is younger (no more than 200 million years old) than some found on the Earth’s surface (4 billion years). Find out the reasons for this difference. Start by looki
  • • Assessment: Ask students to explain their maps and to identify their features. Listen for oceanic geographic terms. </P>