Asked by rafa to Anna, Daniel, Denise, Jesse on 25 Jun 2014.
Keywords: chemistry, lava, magma
Hi rafa, this is really a technical question, and I have to admit I have no tools to answer. I’ll be learning this with you from the other scientists!
thanks for asking
To be honest, unfortunately, I have never researched this topic as such, so I am really sorry about it, but I would not know the answer to it! 🙂
Magma chemistry at a volcano can be similar through time and space or different. If the chemistry of the magma in a shallow magma chamber is pretty homogeneous (the same throughout) then you would expect the lava to be similar chemically. However, the lava that comes out of the volcano can have a different chemistry in various ways.
One way is that magma in the chamber will crystalize first the minerals that crystalize at higher temperatures. These minerals will be heavier that the melt and sink to the bottom of the magma chamber. This will change the chemistry of the magma because the composition of the crystallized minerals have been removed from the melt. So, when the magma erupts to the surface, the lava will have the different composition than the original magma. Also, when the magma in the chamber melts rocks (with another composition) at the walls of the chamber, it will incorporate the chemistry of those rocks to the chemistry of the magma. And when the lava comes out, it will have the chemistry of the wall rock incorporated in it.
So, in summary magma and lava can be different due to the processes in the magma chamber, but they can be similar if the magma chamber is shallow, there is no magma crystallization in the chamber and no wall rock incorporated in the the magma.
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