How do continental crust and oceanic crust differ?
Check all that apply.
A Continental crust is composed of granite; oceanic crust is composed of basalt.
B Continental crust is less dense than oceanic crust.
C Continental crust is thicker than oceanic crust.
D ceanic crust is composed of granite; continental crust is composed of basalt.
E ceanic crust is thicker than continental crust.
F ceanic crust is less dense than continental crust.
The correct answer and explanation is :
The correct answers are:
✅ A Continental crust is composed of granite; oceanic crust is composed of basalt.
✅ B Continental crust is less dense than oceanic crust.
✅ C 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 differ in composition, density, and thickness.
- Composition
- Continental crust is primarily composed of granite, which is rich in silica and aluminum (often referred to as “sial”).
- Oceanic crust is primarily composed of basalt, which is richer in iron and magnesium (called “sima”).
- This makes continental crust lighter in color and less dense compared to the darker, denser basaltic oceanic crust.
- Density
- Continental crust is less dense than oceanic crust.
- The density of continental crust averages 2.7 g/cm³, whereas oceanic crust is denser, averaging 3.0 g/cm³.
- Because of this difference, oceanic crust tends to sink below continental crust during subduction at tectonic plate boundaries.
- Thickness
- Continental crust is thicker, averaging 30–50 km, and in some mountainous regions, it can be over 70 km thick.
- Oceanic crust is thinner, typically around 5–10 km thick.
Incorrect Options:
❌ D Oceanic crust is composed of basalt, not granite.
❌ E Oceanic crust is thinner, not thicker than continental crust.
❌ F Oceanic crust is denser, not less dense than continental crust.
These differences are crucial in understanding plate tectonics, earthquakes, and the formation of geological features like mountains and ocean trenches.