Question

Explain in a few sentences why earthquakes and volcanoes occur together at location 1, but not together at location 2, based on plate tectonic theory.

Identify two different areas anywhere on Earth:

(1) a location where earthquakes and volcanoes occur together in the same location, and (2) a location where either earthquakes or volcanoes occur alone, but not together.

Compare your two locations. Think about the three different types of plate tectonic boundaries, and what causes earthquakes and volcanoes.

Answer 1

The volcanoes and earthquakes occur together many a time. These occuring together depends on the tonic setting. In most cases the two phenomena occur together at Convergent plate boundaries where oceanic plate is subducting under a Continental plate. The undergoing plate melts and creates pressure, which is released instantly when volcanic eruptions take place, followed by earthquake tremors. The Pacific ring of fire is the best example of such location. That's why most of the volcanic eruptions take place along with Earthquake in Philippines, Indonesia etc. The earthquake zones above Subduction zones where earthquakes and volcanoes occur in high frequency are known as Wadati Benioff zones.

On the other hand volcanoes occur alone on divergent plate boundaries, where explosive eruptions don't take place and only effusive eruptions occur. For instance Iceland which sits astride the mid Atlantic ridge very often experience volcanic eruptions but not Earthquake.

The earthquake most often occur alone at Transform plate Boundaries, where plates move along one another. The friction created by such movement and pressure release in sudden jerks causes the Earthquake to occur. For example at the San Andreas Fault in California and the Anatolian Fault in Turkey.

So we see these three kind of plate tectonic settings determine to a great extent where earthquakes and volcanic eruptions occur together and where in isolation.