What Happens to All That Volcanic Ash?

 All that magma (well, most of it) that is erupting from the volcano is being fragmented into tiny glass shards that we call “ash” and all that ash is being shot into the air at astounding rates – for very large eruptions, it could be as high as 9,500 kg/s for a VEI 7 eruption. In the end, your average eruption is releasing millions to trillions cubic meters of ash into the atmosphere. 

Most of it falls near the volcano (within tens of km), but a significant portion can travel far away, drifting in the atmosphere for hundreds, thousands, tens of thousands of kilometers around the globe. That ash becomes the telltale signs of an eruption that may have much of its record erased by future eruptions or by the relentless powers of weathering, erosion and transport.

Volcanic ash is really just amix of shattered rock, minerals and glass. The shattered rocks are from the physical breaking of the pre-existing material like solidified lava in the conduit (accidental material), while glass is quickly quenched magma from the eruption (juvenile material). 

The minerals could come from either the accidental or juvenile material of the eruption. When you’re trying to identify a layer of volcanic ash, you can look at the shape of the glass shards, the mineralogy of the ash or the composition of the glass
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