The two main types of crust are continental crust and oceanic crust.
These two types differ significantly in their composition, thickness, and density:
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Continental Crust: This type of crust forms the landmasses of Earth. It's generally thicker, ranging from about 30 to 70 kilometers (19 to 43 miles) thick, and is composed primarily of granitic rocks, which are less dense. The average density is about 2.7 g/cm³. Continental crust is also significantly older than oceanic crust, with some rocks dating back billions of years.
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Oceanic Crust: Oceanic crust underlies the ocean basins. It is much thinner, typically around 5 to 10 kilometers (3 to 6 miles) thick. It's primarily composed of basalt and gabbro, which are denser than the rocks that make up continental crust. The average density is about 3.0 g/cm³. Oceanic crust is also much younger, generally less than 200 million years old, as it is constantly being created at mid-ocean ridges and destroyed at subduction zones.
| Feature | Continental Crust | Oceanic Crust |
|---|---|---|
| Thickness | 30-70 km (19-43 miles) | 5-10 km (3-6 miles) |
| Composition | Primarily granitic rocks | Primarily basalt and gabbro |
| Density | ~2.7 g/cm³ | ~3.0 g/cm³ |
| Age | Generally much older | Generally much younger ( < 200 million years) |
| Location | Forms landmasses | Underlies ocean basins |
In summary, continental crust is thick, less dense, and older, forming the continents, while oceanic crust is thin, dense, and relatively young, forming the ocean floors.
