Answers

2015-11-27T17:47:45+08:00
Because of density and pressure. the lower density of the magma relative to the sorrounding rocks causes it to rise (like air bubbles in syrup). it will rise to the surface or to a depth that is determined by the density of the magma and the weight of the rocks above it.
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2015-11-27T18:50:19+08:00
Because of the density and pressure happens under the crust. If there's too much pressure, the lava will come up then an eruption will occur.
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