What causes earthquakes what causes volcanoes?

Answer 1

When big slabs of rock underground called, tectonic plates, move this causes molten rock to rise to the surface. Earthquakes are made by the plates

scraping against each other.

Volcanoes and earthquakes are most probably caused by pressure of water vapour. So intitially, when the earth was too hot the water was in the form of vapour in the atmosphere. When the earth cooled down, the water covered the entire earth's surface. Due to gravity, water percolated inside the earth's surface. Due to to gravitational force it tried to go to the centre of the earth. But due to the heat inside the earth, water also became hot. As you know that under high pressure the boiling point of the water rises. It may go as high as two to five thousands degree celsius. So this very hot water percolated inside the earth. When the pressure of the water increased to the extent than the surface of the earth can hold, the earth's surface was broken and the molten earth and gases came out. This process took place repeatedly, giving rise to present state of the shape of the earth. The movement of the tectonic plates are also, most probably, due to pressure of pocket of water vapour only. Depending on the depth of the blast and the upper coat of the earth you have volcanoes or earthquakes of different intensity. This indicates that when you see volcanoes on the surface of the planets, it means that they have water inside them.

Answer 2

Earthquakes are caused due to the deformation of the Earth's crust which occurs die to the movement of the lithospheric tectonic plates. Where these plates collide with each other or slide past each other (at convergent and transform boundaries), stress builds up within the crust. When this stress exceeds the strength of the crust or the fault zone, a rupture occurs where the fault zone suddenly moves, releasing all the stored energy as seismic waves, causing an earthquake.

Volcanoes occur where mantle material melts. This tends to happen at a number of places. These include above convergent boundaries where subduction occurs, at spreading or divergent boundaries and above mantle hotspots.

Subduction zones create volcanic activity because the slab of lithosphere which is being subducted transports volatiles including water down into the mantle. Water and other volatiles exsolve from hydrated minerals and escape into the mantle material where they drive down the melting temperature of the mantle rocks. This causes melting to occur and the resultant melt or magma migrates upwards towards the surface causing volcanism.

Spreading or convergent boundaries cause volcanism due to a process known as decompression melting. This occurs because the lithosphere over a spreading centre is thinner than normal and so there is less material pushing down on the mantle material below (there is a lower vertical in-situ stress). This acts to lower the melting temperature of the underlying mantle material causing melting and the formation of magma leading to volcanic activity.

Finally hotspots are points within the Earth's upper mantle that are at a much higher temperature than normal. This is thought to be caused by an upwelling of high temperature material from deep within the mantle (possibly from near the boundary with the Earth's core)* which causes melting of the shallow mantle material and the crust again leading to volcanism.

* There is currently a debate within the geophyscis community about the importance of mantle plumes in hot spot volcanism, the exact nature of mantle plumes and whether or not they even exist!

Answer 3

Volcanoes are caused by the movement of vast slabs of rock called plates. When the rock comes together it forces molten rock from deep underground to the surface.

Answer 4

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