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In an Explosive eruption, where does all the gas come from? Does it come from pockets in the ground, and if so, how does it get there? --The High Fin Sperm Whale (talk) 21:25, 1 June 2009 (UTC)[reply]

Usually it was already dissolved in the magma (see e.g. [1]), but evaporating groundwater is another possibility. -- Avenue (talk) 01:08, 2 June 2009 (UTC)[reply]

But how does it get dissolved in the magma? And also, where does it come from before it dissolves in the magma (because such chemicals as hydrogen fluoride and hydrogen sulfide never occour naturally except underground)? --The High Fin Sperm Whale (talk) 21:10, 17 June 2009 (UTC)[reply]

Many volcanoes are caused by the the movement of the continental plates leading to the subduction and burying of sea floor. The buried sea floor material will obviously contain quite a lot of water. Above 375deg water cannot exist as a liquid and it becomes a gas although at the pressures involved in the magma it still occupies only a smallish volume. That is until the pressure is relieved when it expands explosively. Similarly fluorine is one of the commoner elements in the earth's crust, 950ppm. Hope this helps.ping (talk) 22:25, 18 June 2009 (UTC)[reply]

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Normally, in a submarine context, this type of volcanic activity results from the collision between lithospheric, oceanic and continental plates, where the denser oceanic plate subducts, in which it takes water that lowers the melting point of the magma and increases its viscosity, due to the salinity present in it. The associated magma is acidic, rich in silica and viscous. 2001:818:E2C1:2700:D084:96BC:4543:B06A (talk) 09:29, 5 February 2023 (UTC)[reply]