* Oceanic Crust: Thinner, denser, and composed primarily of basalt. It's constantly being generated at mid-ocean ridges and ages as it moves away from the ridge.
* Continental Crust: Thicker, less dense, and composed mainly of granite.
The Subduction Process:
1. Collision: When oceanic and continental plates collide, the denser oceanic plate bends and slides under the continental plate.
2. Subduction Zone: The area where the oceanic plate descends beneath the continental plate is called a subduction zone.
3. Melting: As the oceanic plate plunges deeper into the mantle, it experiences intense heat and pressure. This causes some of the rock to melt.
4. Magma Formation: The molten rock, called magma, rises through the overlying continental crust.
5. Volcanoes and Earthquakes: The rising magma often erupts to the surface, forming volcanoes. The movement and interaction of the plates also generate earthquakes.
Why is oceanic crust denser?
* Composition: Oceanic crust is primarily made of basalt, a dense igneous rock. Continental crust is mostly made of granite, which is less dense.
* Age: As oceanic crust ages, it cools and becomes denser. The older oceanic crust at subduction zones is denser than the relatively young continental crust.
In summary, the density difference between oceanic and continental crust drives the subduction process. The denser oceanic plate sinks beneath the less dense continental plate, leading to a chain of events that shape our planet's surface.
