Science Olympiad Dynamic Planet Practice Test

What type of crust is thicker and less dense, primarily found above ocean levels?

1. Oceanic crust

2. Continental crust

3. Transitional crust

4. Primitive crust

The correct answer is: Continental crust

The thicker and less dense type of crust primarily found above ocean levels is the continental crust. This crust is composed predominantly of granitic rocks which are lighter and thicker compared to oceanic crust. Continental crust typically ranges in thickness from about 30 to 50 kilometers, while oceanic crust is generally only about 5 to 10 kilometers thick. The differences in density play a crucial role in the formation of the Earth's surface features. Because the continental crust is less dense, it "floats" higher on the mantle compared to the denser oceanic crust, which is why continents are elevated compared to ocean basins. This property leads to the formation of mountains and highland regions on land. In contrast, oceanic crust consists mainly of basaltic rocks, which are denser and thus contribute to the lower elevation of ocean floors. Other types of crust such as transitional and primitive crust do not have a recognized status in standard geological classification in the same way as oceanic and continental crust do, making them less relevant for this specific question.