Volcano
Topic: Interior of the Earth: Earthquakes, Volcanoes and the Layered Earth · NCERT: Class 9, Ch 2 "Shaping of the Earth's Surface"; Class 11, Ch 3 "Interior of the Earth"
Meaning
A volcano is an opening in the earth's crust through which gases, ash and molten rock escape to the surface. Underground the molten rock is called magma. Once it moves towards or reaches the surface it is called lava. Volcanoes are classed by how they erupt (calm or explosive) and the shape they build (for example shield, composite, caldera).
- Active: erupting now or has erupted recently.
- Dormant: quiet, but may erupt again.
- Extinct: not expected to erupt again.
Most volcanoes lie along plate edges, especially around the Pacific "Ring of Fire".
Example
Barren Island in the Andaman Sea, about 140 km north-east of Port Blair, is India's only confirmed active volcano. Narcondam, to its north, is generally classed as dormant.
Don't confuse with
- Mud volcano: pushes out mud, water and gases (mainly methane), not molten rock. India's best known is on Baratang Island in the Andamans.
Related concepts
- Magma
- Lava
- Pyroclastic material
- Active volcano
- Shield volcano
- Cinder cone
- Composite volcano
- Caldera
- Supervolcano
- Flood basalt province