04 Earthquakes and their types
An earthquake is huge stored energy released suddenly from inside the Earth as elastic waves and vibrations that travel through the rocks and cause destruction in the crust.
Focus and epicentre
- The focus is the point inside the Earth from which the energy is released.
- The epicentre is the point on the surface lying vertically above the focus, where the effect is usually most severe.
Types of earthquakes
- Volcanic earthquakes: local tremors that accompany volcanic activity and do not extend far.
- Tectonic earthquakes: the most common and most destructive type; they occur in zones of rock fracturing and plate sliding along faults.
- Plutonic (deep-focus) earthquakes: their focus lies at great depth, sometimes more than 500 km below the surface.
Comparison
- Cause — volcanic: volcanic activity · tectonic: plate and fault movement · plutonic: great depth in the mantle.
- Spread — volcanic: local · tectonic: widespread · plutonic: deep focus.
- Frequency and damage — volcanic: limited · tectonic: most common and most destructive · plutonic: less surface effect because the focus is far away.