Earth’s land, the hard rock shell on its surface, is called the crust. Any part of the Earth’s crust that rises above the oceans is called continental crust. Any part of the Earth’s crust that is covered by the oceans is called oceanic crust.  If you could drain the ocean water away you would be able to see the oceanic crust, the land, under the oceans.


Earth is sometimes called the “water planet” because so much of its crust covered with water. Most of that water is in Earth’s oceans. How much of the Earth’s crust is covered by the oceans? About 70% of the Earth's crust is oceanic crust.


In this investigation your students see how good they are at estimating the amount of oceanic crust under Earth’s oceans. Students can work alone, in teams or in groups. Younger students can use word descriptions (some, a little, most, etc.) or simple fractions for their estimates. Older students can use fractions or percentages for their estimates.


More math centered procedures for older students include:


What you need:

What to do: Student Procedure


The National Geographic Channel used computer models and drained the oceans. Want to see what some of that ocean crust looks like? View some video clips and more from Drain the Oceans.


What else do you want know about Earth’s ocean land? Make a list of your questions and see what you can find out. Here’s a place to start learning about Earth’s ocean land. You might even find out the answer to the question “How much of Earth’s crust is covered by ocean water?”