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Volcanic Pyroclastic flows: What are some good analogies to understand the full spectrum of causes? (self.askscience)

submitted 1 year ago by j4k3 to c/askscience

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I'm trying to wrap my head around something that appears far more complex than I first thought. I don't understand the explosive elements and chemistry that drives ash production and the heat to create the eruption column. I'm aware of how molten metal behaves in a foundry crucible with flux and degassing required. So I understand how magmas can have a tremendous amount of dissolved elements that can release like CO2 from a shaken soda bottle being opened. I can picture this kind of pyroclastic flow easily; the "shaken soda bottle" type.

I don't have a very good grasp of how the ash column can reach enormous heights and then collapse, or how composition impacts this kind of collapse. I just can't picture in my mind how this type of collapse results in a flow, like some kind of avalanche or pronounced river of material as opposed to more of a micro-regional rain like ash fall event that is very intense and superheated. What is the trigger and how does it overcome any hotter material lower in the column?

https://en.m.wikipedia.org/wiki/Pyroclastic_flow

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[–] weariedfae 2 points 1 year ago (1 children)

Here are some resources to clear up the difference between eruptions and flows and provide more context to answer your question.

Background on explosive eruptions: https://youtu.be/tQzaQd72DJI?si=wmhLU3TjlRuiKvJW

Part 2 (more interesting from my pov): https://youtu.be/umNWZOTHFXo?si=ZfmHJCEnQ_eil87I

Timestamp ~30:10 on the second video (Lesson 10) talks about the origin of pyroclastic flows.

[–] j4k3 2 points 1 year ago

Thanks. I watched both of them. That cleared up the missing pieces.