Why is there glass in the volcanic ash?

[flobadob]

It says that the ash coming from the volcano in Iceland contains glass. Is this the result of some sort of chemical combination or how does it come to be in it?

[Clanad]

Strictly speaking, it's only the heat generated within the Earth that melts various silicate minerals and forms the molten magma... When the magma is cooled very quickly, as during the eruption of a volcano, it doesn't form crystals, but rather obsidian type rocks, which fracture easily in the violent eruption, into smaller, glass particles from the size of dust up to much larger rocks. We've found (here in the western U.S.) boulders of obsidian the size of a small car. These weather and break into much smaller pieces quickly (relatively speaking) unless buried in the intial pyroclastic outflow...

[lardhelmet]

I asked OH the same question this morning and he gave me kind of the same answer as clanad. I just thought someone had been chucking their empties down the hole & the volcano was now spitting them all out again!

[lardhelmet]

That's also what OH said Eddie - he used to be a pilot

[flobadob]

Good enough. Who is OH, out of interest?