Question: .does lava / magma turn into crystal or something like that ?? .is the gas / smoke around a volcano hot ??

James Hickey answered on 12 Nov 2013:

Hi miffyjam! A double question – nice!

You’re right, yes. When lava or magma cools down, some of the stuff that makes it solidifies into crystals. Magma is the word we use for molten rock that stays beneath the Earths surface – this cools down slowly and big crystals can form. Lava is what magma becomes when it pours out onto the Earths surface – here the lava cools down quicker and only small crystals can develop. You can see an example of green olivine crystals in a lava here: http://chemistry.about.com/od/geochemistry/ig/Green-Sand-Beach/Olivine-in-Lava.htm

On an active volcano (one that is erupting) gases escape in various ways. The most obvious are the big eruption columns that you see going into the sky. These are definitely hot as they are escaping from magma that is around 1000 degrees! The heat is also what helps drive the columns so high up into the sky. In other types of eruptions you can get very, very fast flows of mixtures of gas and rock called pyroclastic flows. These are also extremely hot! It was a pyroclastic flow that destroyed the ancient city of Pompeii in Italy.

On non-active volcanoes, gases can also escape very peacefully. This may just look like a wispy cloud when viewed from a distance but it is in fact a mixture of carbon dioxide (CO2), water vapour, sulphur dioxide (SO2) and other such things. These gases are not very hot, just a little bit smelly…