Which of these statements is correct?
A. Continental crust is thinner than oceanic crust.
B. Continental and oceanic crusts have the same thickness.
C. Oceanic crust is thicker than continental crust.
D. Continental crust is thicker than oceanic crust.
The correct answer and explanation is:
The correct answer is: D. Continental crust is thicker than oceanic crust.
Explanation:
The Earth’s crust is divided into two main types: continental crust and oceanic crust. These two types differ significantly in thickness, composition, and density.
- Thickness: Continental crust is much thicker than oceanic crust. On average, continental crust is around 30 to 50 kilometers thick, although it can be even thicker in some areas like mountain ranges (up to 70 kilometers). In contrast, oceanic crust is much thinner, typically ranging from 5 to 10 kilometers in thickness.
- Density: Oceanic crust is denser than continental crust. It is primarily composed of basalt, which is a denser rock compared to the granite that makes up the majority of continental crust. This difference in density contributes to the continental crust floating higher on the Earth’s mantle, while oceanic crust lies lower, forming the ocean basins.
- Composition: Continental crust consists mainly of lighter rocks like granite, while oceanic crust is primarily made up of basalt. The composition further contributes to the differences in their properties and behavior during geological processes like subduction, where oceanic crust is often forced beneath continental crust due to its higher density.
In summary, continental crust is thicker than oceanic crust by a significant margin. This distinction is one of the key factors that influences the structure of the Earth’s surface, including the formation of mountain ranges, ocean basins, and the behavior of tectonic plates.