The Ocean Floor

The ocean floor is covered with mountains, valleys, plains, and other features similar to the land surfaces of earth.  The ocean’s features, like land features, are a result of tectonic processes from deep inside the earth.

This is a generic diagram of the types of features that can be found on the ocean floor. Image from Wikimedia, public domain.

The earth is made up of a hot inside and big plates of crust covering the outside.  These plates spread apart and squish together and grind past one another.  These actions cause the crust to buckle, fold, and split, which makes mountains and valleys.

The red areas on this image show the newest ocean crust and the dark blue shows the oldest ocean crust. The red areas are where the sea floor is spreading at the edge of tectonic plates. At these seams in the crust there are underwater mountain ranges or ridges.  Image from the NOAA, public domain.

There are volcanoes under the oceans just like there are on land.  These volcanoes can build up into mountains, sometimes breaking the surface as islands.  The Hawaiian islands began as undersea mountains.

This is lava spilling into the sea from Mauna Loa, the volcano that has formed the island of Hawaii. Image by Brocken Inaglory, Wikimedia, CC license.

Trenches are formed in places where one ocean plate is being pulled under, or subducted, beneath another ocean plate.

This is a cross section diagram of the Mariana trench, the deepest place on earth. The seam where one plate is pulled under another leaves a deep valley. US government supplied image, redrawn into SVG by Vanessa Ezekowitz, CC license, Wikimedia.

Here is an Ocean Floor Map.  It shows some of the major mountain ranges and trenches that can be found under the sea.

A free printable map of the ocean floor to label and color.

Use a student atlas to label the ridges, ranges, and trenches that are shown on the map.  You can label other features that you find as well.  The trenches are shown as Vs. Color the trenches dark blue or dark purple.  The mountains are shown as upside down Vs.  Color the mountains brown.  Color the sea blue.

A free printable map of the ocean floor to label and color.

Additional Layers

  • The mapping of the sea floor only began in WWII with the large-scale submarine warfare it introduced.  Learn more about Harry Hess and his discoveries.
  • Find out what a guyot is and how they are formed.
  • The oceans are still mostly unexplored.  Scientists are finding new mountains, new species of animals and plants, and new principles of physics and geology on a  regular basis.  Search online to find the most recent news about ocean discoveries.  Here is a news article about some newly discovered sea creatures.



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