Deep underground the rocks
are pressed together and become so hot they melt. This melted rock
is called magma.
Sometimes the magma rises and collects
in large pocket in the crust and mixes with
gas. The heat causes pressure and the magma is pushed through cracks in
the crust. This is called an eruption and the crack it comes from
is called a volcano.
When the magma erupts out of the top
of the volcano and is on top of the Earth's crust it is called lava.
When an eruption happens, hot rocks, sparks, dust and steam are thrown
into the air.
There are different types of volcanoes.
Some of these are:
Shield volcanoes: These form when thin,
runny lava oozes out and spreads widely over a period of time.
Cinder cone: This is a small, steep
volcano made up of harderned ash, cinders and small lava lumps.
Caldera : This forms when a violent
eruption blows off the top of an existing volcano.
An active volacno is one that erupts
regularly. A dormant volcano is one that has not erupted for a long
time but it might erupt again sometime. An extinct volcano is one
that is dead and it will not erupt again.
Volcanoes usually occur on fault lines
which are moving apart. They make new land. When this happens
under the ocean, islands are formed. Other things that show there
are active volcanoes are geysers and hot springs. There are no active volcanoes
in Australia, but in New Zealand in the Rotorua area there are many volcanic
craters, geysers and hot springs.
Click HERE
to see our model volcano.
