Laccolith
Also called: Lacolith · Topic: Interior of the Earth: Earthquakes, Volcanoes and the Layered Earth · NCERT: Class 11, Ch 3 "Interior of the Earth"
Meaning
A laccolith is a large, dome-shaped mass of igneous rock that formed inside the crust. Its base is flat and its top is arched like a dome. A pipe-like channel feeds it with magma from below. The magma pushes the rock layers above it upwards into a dome. It is like a composite volcanic dome, but it formed underground. It shows at the surface only after erosion removes the rocks above it.
Example
Many of the exfoliated granite domal hills of the Karnataka plateau are laccoliths or batholiths. Exfoliated means the outer rock peels off in sheets, like the layers of an onion.
Don't confuse with
- Batholith: much larger and deeper. It is an old magma chamber and has no flat base.
- Lopolith: shaped like a saucer that dips down in the middle. A laccolith arches upwards.