Why does a volcano erupt?

Answer 1

A volcano erupts when the pressure within the molten magma below the surface becomes stronger than the strength of the rocks on the surfacethat make up the volcano. The magma then finds the path of least resistance to the surface and erupts. That pressure comes both from the buoyancy of the magma and from gas bubbles inside the magma that want to expand.
The magma pressure comes from the expansion of gas bubbles that are within the magma.
The heat source for all erupted materials comes from natural radioactive decay within the Earth. The concentration of radioactive elements in the Earth is not really very high, but the volume of the Earth is great enough so that there is enough of a contribution of heat from the decay to produce melting. The material that melts (magma) has a lower density and it migrates to the surface to erupt.

Answer 2

A volcano will erupt when the pressure from the magma inside is greater than the strength of the sides of the volcano. The pressure inside can increase if there is a lot of magma coming up into the volcano from down in the Earth's mantle. The pressure can also increase because as magma sits in the volcano, gas bubbles escape and try to expand (just like in a soda). Eventually the pressure gets to be so great that the combination of the strength of the rocks making up the volcano and their weight is not enough to hold the magma in and you get an eruption. If the volcano lets the pressure build up really high before an eruption then the eruption is probably going to be explosive. If the volcano is weak and only a little pressure causes an eruption then the eruption will be not very explosive.

Answer 3

A volcano is a geological landform on the surface of the earth (and other planets) where magma from the planet's interior erupts (or once erupted) to the surface. Roughly defined, a volcano consists of a magma chamber, pipes and vents. The magma chamber is where magma from deep within the planet accumulates, while pipes are channels that lead to surface vents, openings in the volcano's surface through which lava is ejected during an eruption. Some volcanoes produce material which builds up into a large mountain-like structure, other types of volcano form different landforms.

Answer 4

Volcanoes erupt when the pressure of the magma inside the chamber gets too high and this energy is vented in a volcanic eruption. Sometimes lava explodes out the top of the volcanoe but it also reaches the surface through side channels in the volcanoe. Predicting volcanic eruptions is definatly not an exact science but it is thought that the disruption caused by an earthquake can prompt a volcanoe to erupt

Answer 5

The best way to describe what happens when a volcano erupts is to shake a bottle of fizzy pop. This shaking builds pressure caused by a chemical reaction. When you open the bottle, the pop squirts out. This is what happens when a volcano erupts. The magma builds up in its chimney and mixes with gas formed from melted rock. This mixture is light and rises to the top. When it reaches the top, it explodes from the cone of the volcano. The pressure of the gases in the magma causes the volcano to erupt.

Answer 6

Usually a build up of pressure below the Earths surface. Hot gases build up as a result of the rock which makes up the Earths crust melting beneath the surface, creating pressure in the crust. If a volcano already exists, it will burst through the old gap, usually, otherwise a new volcano will form. Hawaii is slightly different, in that it is a weakness in the earths crust on a hotspot for geological activity. So it spills out magma because the crust isnt strong enough to keep it in.

Answer 7

The earth surface temparature is cooler than that below!
So often, the magma/lava that reaches the surface cools and solidfies, thus blocking the very orifice from which it oozed out.
This leads to a pressure cooker situation and the volcano erupts or blows its top, so that the molten lava inside can escape!

Answer 8

when ACTIVE, volcano's erupt (pressure) to vent out lava materials aka built up gases and other materials

Answer 9

Simply, as pressure in the subduction zone increases, the pressure intenses which causes the magma to increase in scale and intensity. As pressure continues to increase, it forces itself upwards, causing the the releasement of the magma - simply its all down to "INCREASING INTERNAL PRESSURE!!!!"

Answer 10

Pressure, laddie. Pressure.