Headings Igneous
Rocks Search Questions 
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Igneous Rocks - Basalt.
When molten magma cools quickly, it can crystallise to form basalt.
Molten magma from the
mantle
can reach the outside of the
Earth through a volcano.
When it gets to the Earth's surface it
cools rapidly
and can form a dark rock containing many small
randomly arranged
interlocking crystals.
Basalt is an example of this type of rock.
It is called an extrusive igneous
rock
because the molten magma has been forced
out of a volcano.
Extrusion means "squeezing" or "forcing
out", like toothpaste from a
tube.
In the right
conditions,
basalt may crystallize in the shape of hexagonal
columns.
There are famous examples of this
at
Fingal's Cave on Staffa Island, the Inner
Hebrides, Western
Scotland,
and the Giant's Causeway, County Antrim, Northern
Ireland.
Basalt can also form during sea floor
spreading,
where two
plates move
apart beneath an ocean
(see Plate Tectonics on the GCSE Physics site).
Headings Igneous
Rocks Search Questions
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