Science Olympiad Dynamic Planet Practice Test

What is the average density of continental crust compared to oceanic crust?

1. Continental crust is denser than oceanic crust

2. Continental crust is less dense than oceanic crust

3. Both have the same average density

4. Continental crust is significantly less dense

The correct answer is: Continental crust is less dense than oceanic crust

The correct answer highlights that continental crust is generally less dense than oceanic crust due to the differing compositions and characteristics of each type of crust. Continental crust is primarily composed of lighter, granitic rocks, which have a lower density compared to the basaltic rocks that make up oceanic crust. This difference in composition results in continental crust having an average density of about 2.7 grams per cubic centimeter, while oceanic crust has an average density of approximately 3.0 grams per cubic centimeter. The less dense nature of continental crust enables it to "float" higher on the mantle compared to oceanic crust, contributing to the continental shapes and geological features we observe today. Understanding these density differences is crucial for comprehending tectonic processes, such as subduction and mountain building, which are integral components of plate tectonics and Earth’s geological activity.