Science Olympiad Dynamic Planet Practice Test

What defines oceanic crust in comparison to continental crust?

1. It is older than continental crust

2. It is composed mainly of limestone

3. It is denser and formed from erupted mantle material

4. It has a higher elevation above sea level

The correct answer is: It is denser and formed from erupted mantle material

Oceanic crust is primarily defined by its density and composition compared to continental crust. Oceanic crust is denser because it is composed largely of basalt, which originates from mantle material that has erupted at mid-ocean ridges. This basaltic rock has a higher density than the granitic composition of continental crust, which includes a larger percentage of lighter materials. As a result, oceanic crust generally sits lower in elevation compared to continental crust, which contributes to the formation of ocean basins. The process of formation for oceanic crust differs significantly from that of continental crust, as the latter can experience complex geological processes over time, resulting in its variety of rock types and older age compared to most oceanic crust. The younger formation of oceanic crust occurs through volcanic activity along mid-ocean ridges, leading to its distinctive features and density characteristics. Understanding these differences is important in the study of plate tectonics and the geologic processes that shape the Earth's surface and structure.