Question: Why doesn't lava solidify inside a volcano?

Rebecca Williams answered on 25 Jun 2014:

Hi Alberteinstein,
You ask some really great questions!

It does! Lava does sometimes solidify in volcanoes. Magma chambers aren’t actually swirling vats of molten rock. They are more like hot areas where you have some molten rock and some solid rock. A bit like a wet sponge has some solid spongey areas and some liquid water areas.

Magma chambers remain active and able to continue to make volcanoes if there is always some molten rock in that sponge. So, it needs to be attached to a source for the molten rock. If you go back to Rhiana’s question about where magma comes from you can find out about those sources of moletn rock. (/praseodymiumj14-zone/2014/06/24/where-is-the-lava-coming-from/) This means that the magma chamber needs to continue to get melted mantle from a mantle plume, or from a subduction zone, or from a spreading centre. If this supply of fresh hot magma gets cut off, the magma will solidify in the magma chamber.

Sometimes, magma chambers just never make it to the surface as volcanoes because the Earth’s crust is too thick. So, they just cool down and solidify. This is where the granite rock that we have in the Malverns, Cornwall and the Lake District come from. They are like failed volcanoes.

Finally, sometimes the lava just doesn’t have enough oomph to erupt from the volcano so it will freeze in the vent of the volcano. This is called a volcanic plug. They make really cool landforms because the material around them gets eroded away so you get a plug of hard rock stood up out in the middle of nowhere. Take a look at the images of volcanic plugs here: https://www.google.co.uk/search?q=volcanic+plug&rlz=1C1OPRB_enGB524GB530&espv=2&source=lnms&tbm=isch&sa=X&ei=zM-qU-vhF67T7AbjwICgDw&ved=0CAYQ_AUoAQ&biw=1680&bih=949

Edinburgh Castle is built on top of a volcanic plug!