Why volcanic eruption occur?

Answer 1

Volcanic eruptions occur due to partial melting of the rock in the earth's mantle. This melted portion is of a lower density than the rest of the mantle material and so rises towards the surface. This causes a build up of pressure which ultimately leads to the melt (or magma) forcing its way to the surface where it erupts as lava forming a volcano.

Answer 2

a volcano occurs on a plate boundary between tectonic plates, and when these two or more plates push together the land rises up forming either a volcano or a mountain, depending on the situation. Volcanoes erupt when the pressure of the magma beneath them becomes too great, and is forced out of the volcano. the force of the volcano depends on how much pressure builds up. for example, so volcanoes slowly release lava continuously, so they never explode. others, like Krakatoa, build up pressure for a long time until it becomes too great and the explosion blows most of the volcano away and sends shockwaves around the earth, and ,like Krakatoa, can disrupt global weather systems for up to a year or more. A greater example of pressure is the Yellowstone Caldera. This Super-Volcano, whose underground crater covers the whole of the Yellowstone Park, is building up immensely great pressure. as the pressure to make it erupt will have to be so great, chances are that when it erupts it will be a global apocalyptic event.

Answer 3

Volcanic eruptions occur because of 3 main reasons:

1.Techtonic Plates' Divergence(pulling apart) and Convergence(coming together).
Divergence E.g. Mid-Atlantic Ridge.
Convergence E.g. Pacific Ring of Fire.

2.Stretching and thinning of the Earth's crust (called "non-hotspot intraplate volcanism").E.g. the African Rift Valley, the Wells Gray-Clearwater volcanic field and the Rio Grande Rift in North America and the European Rhine Graben with its Eifel volcanoes.

3. Mantle Plumes(called"hotspots").E.g. the Hawaii volcanoes.

Answer 4

The interior of the Earth is hot. The heat comes from the decay of radioactive materials mixed into the rocks. This doesn't produce much heat, but in the interior of the Earth there is no way for the heat that is produced to escape, except slowly to the surface. Therefore the heat builds up over time to the point where most of the interior of the Earth is at least semi-molten.

This heat is enough to melt rock in some areas. It comes to the surface in at least three ways:

Beneath the oceans, along what is known as a mid-ocean ridge, the Earth's crust is pulling apart and slowly spreading. Molten rock rises into the cracks this forms as volcanic lava flows. This kind of volcano shows up in some mid-ocean islands and, notably, in Iceland. The lava here is basaltic; basalt is a dark, heavy rock typically making up the crust beneath oceans.

In some places it appears that slow rising columns or currents of especially hot material are coming to the surface from deep inside the Earth. These melt whatever is in their way, causing isolated volcanic hot spots such as the Hawaiian Islands or the volcanic area currently centered around the Yellowstone Park area in the United States.

In some areas, notably along some coasts of continents, there is a "subduction zone" where older oceanic crust is sinking down under the edge of another crustal plate. Often this will be oceanic crust, which is made of denser rock, going beneath continental crust, which is made of less dense rock. Naturally, if one or the other of these is going to get pushed underneath, it tends to be the denser one. When this happens the minerals in the sinking crust heat up and start to melt. The first minerals to melt are, of course, the ones with the lowest melting temperature, and these also tend to be the lightest and least dense. As they melt, the liquified rock is lighter than what's around it and tends to ooze upward toward the surface, eventually bursting out at the surface as volcanic eruptions. This is where the classic "cone type" volcanoes form, such as Mount Fuji, Mount Ranier, Krakatoa, Mount Saint Helens, Vesuvias, Mount Atlas, and a myriad of others.

The volcanoes at the center of an ocean tend to be well behaved because basaltic lava, when it comes out of the ground, tends to be nicely liquid. It makes low, broad volcanoes. The lava that forms when one plate sinks under another and starts to melt is not so well behaved. This kind of volcano can erupt unexpectedly and violently-- or even explode; look up what happened to Krakatoa if you'd like to know how bad this can be. And keep in mind that we have geological evidence of worse cases than that.

Answer 5

pressure in the earths core obeys einstines e=m theory

Answer 6

Because The earths plate tectonics form subduction and magma rises