In geography, the crust refers to the outermost solid shell of a terrestrial planet, like Earth.
The Earth's crust is not a single, uniform layer. Instead, it's divided into two primary types:
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Continental Crust: This is the thicker, older, and less dense part of the crust that underlies the continents. It's primarily composed of granitic rocks.
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Oceanic Crust: This is the thinner, younger, and denser part of the crust that underlies the ocean basins. It is primarily composed of basaltic rocks.
Here's a table summarizing the key differences:
| Feature | Continental Crust | Oceanic Crust |
|---|---|---|
| Thickness | Typically 30-70 km | Typically 5-10 km |
| Age | Older (up to 4 billion years) | Younger (typically less than 200 million years) |
| Density | Less dense | More dense |
| Composition | Primarily granitic | Primarily basaltic |
The dynamics of Earth's crust are driven by plate tectonics. The crust is broken into several large and small plates that move and interact with each other. These interactions are responsible for various geological phenomena, including:
- Earthquakes: Occur when plates slip past each other along faults.
- Volcanoes: Form when magma from the mantle erupts onto the surface, often at plate boundaries.
- Mountain Building: Occurs when plates collide and buckle the crust.
- Sea Floor Spreading: Occurs at mid-ocean ridges, where new oceanic crust is formed.
In summary, the crust is the Earth's outermost layer, characterized by distinct continental and oceanic components, and is constantly reshaped by plate tectonic processes.
