Q.17. Discuss the causes of volcanic eruption and describe the land-forms formed by deposition of its lava.

Volcanic eruptions are primarily caused by the movement and interaction of tectonic plates and the buoyancy of magma. Here are the main causes:

1. Tectonic Plate Movement: Most volcanoes are located at tectonic plate boundaries where plates diverge or converge, leading to the formation of magma.
2. Buoyancy of Magma: Magma is less dense than the surrounding solid rock, which causes it to rise towards the Earth’s surface.
3. Pressure from Gases: Magma contains dissolved gases that exert pressure. As magma rises, pressure decreases, allowing the gases to expand and push the magma out.

The deposition of lava from volcanic eruptions leads to the formation of various landforms:

1. Volcanoes: The most obvious landforms, including cinder cones, stratovolcanoes, and shield volcanoes.
2. Lava Domes: Formed by viscous lava that doesn’t travel far from the vent, creating rounded “blob”-like structures.
3. Lava Plateaus: Large, flat areas formed by the flow of less viscous lava over extensive areas.
4. Calderas: Large depressions formed when a volcano erupts and collapses upon itself.

These landforms are testament to the dynamic processes of Earth’s geology and contribute to the planet’s diverse landscapes.