A new study finds that volcanoes are not fed by molten magma formed in large chambers, overturning previous ideas about volcanic eruptions.
Instead, the study finds that volcanoes are fed by so-called ‘mush reservoirs’ – areas of mostly solid crystals with magma in the small spaces between the crystals.
Our understanding of volcanic processes has been based on magma being stored in liquid filled ‘magma’ chambers – large underground caves full of liquid magma. Although, these have never been observed.
Recent studies of magma chemistry have challenged this view, leading to the suggestion of the mush reservoir model, where smaller pools of magma sit in the small spaces between solid crystals. However, the mush reservoir model can not explain how magmas containing relatively few crystals arise and are delivered to volcanoes in order for them to erupt at the surface.
Now, with the new model of mush reservoirs, the research team has come up with a solution. With the mush reservoir scenario, the magma is less dense than the crystals, causing it to rise up through the spaces between them.
As the magma rises, it reacts with the crystals, melting them and leading to local areas containing magma with relatively few crystals. It is these short-lived areas of increased magma which can lead to eruptions.
https://phys.org/news/2018-12-volcanoes-fed-mush-reservoirs-molten.html