Question: Hello, my question is...What occurs when ash is emanated from a large volcanic eruption?

Matthew Pankhurst answered on 17 Jun 2013:

The same thing happens no matter how big the eruption is, which is very useful to know. Ash is actually tiny bits of volcanic glass, that form when magma freezes, and explodes. The glass in your windows are made from something called silica – and this is basically what somes out of volcanoes, expect this glass has other things in it, like aluminium atoms and iron atoms and magnesium atoms. It also has crystals that have grown inside the magma, and bubbles too. Think about when you shake up a bottle of fizzy drink, and let the cap off – suddenly there are heaps of bubbles and a big mess. It’s because there is gas inside the liquid, and when you shake it you put energy into the drink. This energy helps the gas find other tiny bits of gas and team up into bigger and bigger gas pockets – these are the bubbles. When you let the cap off the liquid can’t keep the gas inside it, so it rushes together and because it is lighter than the liquid it bursts out the top! When it bursts out it carries liquid attached the the outside of the bubbles (that’s what makes them bubbles, like the skin of a balloon makes a ballon). The liquid which bursts out of the volcano shatters into tiny shards of glass – this is the ash. Cool huh?! Also, don’t get too close when this is happening!