How do earthquakes vary between oceanic and continental crust?

Earthquakes vary between oceanic and continental crust in terms of their location, intensity, depth, and frequency.

Oceanic crust and continental crust are the two types of tectonic plates that make up the Earth's lithosphere. These plates interact with each other at their boundaries, causing seismic activities known as earthquakes. The nature of these earthquakes can differ significantly depending on whether they occur in the oceanic crust or the continental crust.

Oceanic crust is thinner and denser than continental crust. It is primarily composed of basalt, a type of rock that forms from rapidly cooling lava. Because of its density, when oceanic crust collides with continental crust, it is forced underneath in a process known as subduction. This can lead to deep-focus earthquakes, which occur at depths greater than 70 kilometres below the Earth's surface. These earthquakes are often associated with volcanic activity, as the subducting oceanic crust melts and rises to form magma. The Pacific Ring of Fire, a major area of seismic activity surrounding the Pacific Ocean, is a prime example of this type of tectonic activity.

On the other hand, continental crust is thicker and less dense than oceanic crust. It is primarily composed of granite, a type of rock that forms from slowly cooling magma. When two continental plates collide, neither is dense enough to subduct beneath the other. Instead, they crumple and fold, forming mountain ranges. This process can lead to shallow-focus earthquakes, which occur at depths less than 70 kilometres below the Earth's surface. These earthquakes can be particularly destructive, as their epicentres are closer to the surface and therefore more likely to affect populated areas. The Himalayan range, resulting from the collision of the Indian and Eurasian plates, is a key example of this type of tectonic activity.

In terms of frequency, earthquakes are more common in the oceanic crust due to the higher rate of tectonic activity. However, earthquakes in the continental crust, while less frequent, tend to be more destructive due to their shallower depth and proximity to populated areas. The intensity of earthquakes can vary greatly in both types of crust, depending largely on the specific conditions at the plate boundary.