what is a volcano?

Question

just a basic overview thing...i cant think of one without incorporating all these complicated random stuff about subduction zones and collision boundaries..

Answer 1

Trying to explain this to a kid? :-)

A volcano is a weak spot in the earth's crust where the molten mantle pushes up to the surface. When the molten stuff reaches the surface and comes out of the weak spot, it's called an eruption. After several eruptions the weak spot becomes a hill or mountain called a volcano. Then there's the different kinds/shapes of volcano: shield, strato, and cinder cone.

Answer 2

There are sometimes
weak spots in the
Earth’s crust that may
crack and allow the
magma to flow to the
surface. When this
happens a volcano
forms. The pressure
inside the Earth pushes
the magma upwards.
Sometimes the molten
rock oozes out steadily.
At other times it blasts
out with incredible
force.
To understand this,
think of what happens
when you shake a can
of soft drink. Pressure
builds up inside the
can. When you open the can you release the
pressure, causing an eruption.
After a volcano has erupted and the pressure
has been released, the magma may harden to
form a plug that blocks the vent. When this
happens the eruption stops, and we say the
volcano is dormant, or sleeping. On the other
hand, if the pressure builds up, it may become
active again. If it doesn’t erupt again for a very
long time we say it is extinct, or dead.
There are about 500 active volcanoes around
the world. There are no active volcanoes in
Australia, but there are many extinct ones; for
example, Tower Hill in Victoria, Mt Warning in
New South Wales and Mount Gambier in South
Australia.
When magma reaches the surface it is called
lava. It is usually about 1000 °C, and red-hot.
As it cools, it turns to solid rock. This may take
weeks, or it may happen very quickly if the lava
flows into water. Some volcanoes erupt quietly,
with the lava spreading out to form a flat shieldshaped
volcano. The volcanoes on the Hawaiian
Islands are like this. Sometimes the lava is thin
and runny. At other times it is thick and lumpy,
like porridge, and hardly flows at all.
Volcanoes also produce gases, and some of
these are poisonous. When lava contains a lot
of gas it may froth violently. When this lava
cools, the rock formed is full of holes where the
gas bubbles used to be. Pumice rock is so full
of holes, it is very light and floats on water. You
often see it washed up on the beach.

Answer 3

Well to really explain a volcano you need to talk about subduction zones, at least for stratovolcanoes. But in general a volcano is an opening, or rupture, in the Earth's surface or crust, which allows hot, molten rock, ash and gases to escape from deep below the surface. Volcanic activity involving the extrusion of rock tends to form mountains or features like mountains over a period of time.
Hope this helps

Answer 4

What you need is how to do a summary.

Clearly you have taken the time unlike GRRR so many other posters here (and I mean Yahoo Answers in GENERAL not the responses to your question) to do your research so some hints.

Stuck for a summary?

Take a snack break for a few minutes or switch to another subject for a while then go back to your notes and the question. This should reset your mind so you can focus?
Look for the key words in your notes and the question.
Your summary should be a short definition.

Another thing to bear in mind is if your teacher has shown a preference for one sentence or whole paragraph definitions when marking your previous assignments?

Also you could try combining the best features of several different definitions?

Hope that helps you with a general method you can apply to other topics?

Answer 5

An opening in the earth's crust through which molten lava, ash, and gases are ejected.
A similar opening on the surface of another planet.
A mountain formed by the materials ejected from a volcano.
the definition


http://volcano.und.edu/

Answer 6

A big hole in the terrain, where the land broke, which pours lava, made from very hot rocks. Sometimes this lava forms huge mountains and sometimes explode. The volcano also throws away ashes and smoke. Sometimes they're calm, sometimes they erupt and some of they, eventually die.

Enough basic?
Just joking. :)

Answer 7

An opening on the Earth's surface which allows hot, molten rock or gases top escape from deep below the surface.

Answer 8

magma conduit leading to the earths surface