Rock,
such as the
Manx Group is intruded
by the magma
Fissures form ahead of the rising magma.
These may cool and form dykes
Magma is molten rock
sourced from tens of kilometres below the Earth's surface.
It may cool and solidfy at lesser depths within the crust to form
granite or gabbro,
depending on its composition.
Granite originates tens of kilometres beneath
the earth’s surface. Under the high temperature and pressures
deep within the earth’s crust, rock can melt to form magma. Once
this occurs, the magma may begin to rise up through the crust in a
large body called a batholith. As the batholith rises it begins to
cool causing minerals to crystallise out from the liquid magma. If
the magma cools sufficiently, it eventually solidify completely and
cease to rise. If the magma was originally rich in silica it will
form a granite or if it was poor in silica it will cool to form a
rock called gabbro. Over tens of millions of years, the rock above
the solidified batholith may be eroded away leaving the granite or
gabbro exposed at the surface, such as the Foxdale granite or the
Poortown gabbro.
