Lava
Topic: Interior of the Earth: Earthquakes, Volcanoes and the Layered Earth · NCERT: Class 11, Ch 3 "Interior of the Earth"
Meaning
Lava is molten rock that moves towards or reaches the earth's surface. Underground, the same molten rock is called magma. How lava behaves depends on how runny it is:
- Fluid basaltic lava flows a long way and builds gentle slopes. Eruptions are mostly calm.
- Cooler, viscous lava (thick and sticky) traps gas. It causes explosive eruptions and builds steep cones.
When lava cools at the surface, it forms volcanic rocks such as basalt.
Example
Kilauea in Hawaii pours out fluid basaltic lava that flows for kilometres. This has built a broad shield volcano with gentle slopes. Mount Fuji in Japan, in contrast, erupted thicker lava and built a steep cone.
Don't confuse with
- Magma: molten rock that is still underground in the mantle or crust. It is called lava once it moves towards or reaches the surface.
- Pyroclastic material: solid pieces of rock, ash and bombs thrown out by explosions, not flowing molten rock.
Related concepts
- Volcano
- Magma
- Pyroclastic material
- Active volcano
- Shield volcano
- Cinder cone
- Composite volcano
- Caldera
- Supervolcano
- Flood basalt province