<p>I understand that volcanic ash plumes can only rise to great heights (e.g. 50km) with the help of some other processes, as the velocity of the material ejected isn't great enough to send it high into the atmosphere. </p>

<p>I don't understand how exactly these processes take place. I think that cooler, atmospheric gases are entrained towards the hotter, denser volcanic plume, then become heated and incorporated into the ash plume, causing it to become buoyant and to expand. </p>

<p>What causes the cool, atmospheric gas to move towards the plume? Is it due to the temperature differences between the plume and the atmosphere, or some kind of pressure difference? </p>

CC BY-SA 3.0
2015-03-02T19:18:19.217Z
I am thinking it is just conservation of mass? As the volcanic ash rises the "missing" mass has to be replaced by neighboring atmospheric gases.
Isopycnal Oscillation
<geophysics><atmosphere><volcanology><volcanic-hazard>
What causes the entrainment of atmospheric gases towards a volcanic ash/tephra plume?
nolisgol
# What causes the entrainment of atmospheric gases towards a volcanic ash/tephra plume?

(Asked by: username_0 on 2015-03-01)

I understand that volcanic ash plumes can only rise to great heights (e.g. 50km) with the help of some other processes, as the velocity of the material ejected isn't great enough to send it high into the atmosphere.

I don't understand how exactly these processes take place. I think that cooler, atmospheric gases are entrained towards the hotter, denser volcanic plume, then become heated and incorporated into the ash plume, causing it to become buoyant and to expand.

What causes the cool, atmospheric gas to move towards the plume? Is it due to the temperature differences between the plume and the atmosphere, or some kind of pressure difference?

**Tags:** geophysics, atmosphere, volcanology, volcanic-hazard

> **Comments:**
> **username_1**: I am thinking it is just conservation of mass? As the volcanic ash rises the "missing" mass has to be replaced by neighboring atmospheric gases.  

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## 0 answers

