Earthquakes and volcanoes are sudden events caused by the movement of material inside the Earth. Both are linked to the boundaries of tectonic plates. They are important topics in physical geography and disaster management sections of exams.
Earthquakes
- An earthquake is the shaking of the ground caused by the release of energy.
- The point inside the Earth where it starts is the focus.
- The point on the surface above it is the epicentre.
- Its strength is measured on the Richter scale.
Seismic Waves
- P-waves are the fastest and travel through solids and liquids.
- S-waves travel only through solids.
- Earthquakes are recorded by a seismograph.
Advertisement
Volcanoes
- A volcano is an opening in the crust through which magma erupts.
- Erupted magma on the surface is called lava.
- Volcanoes are of three types: active, dormant and extinct.
The Ring of Fire
- The Ring of Fire around the Pacific Ocean has the most volcanoes and earthquakes.
- Barren Island is India's only active volcano.
Quick Revision Points
- The focus is inside the Earth; the epicentre is on the surface.
- Earthquake strength is measured on the Richter scale.
- P-waves travel through solids and liquids.
- Erupted magma on the surface is called lava.
- Volcanoes are active, dormant or extinct.
- The Ring of Fire lies around the Pacific Ocean.
- Barren Island is India's only active volcano.