How do scientists know that lava and magma come from the earth's
mantle?
Aaron Catrett
Hi Aaron,
Well, in Hawai'i it is easy to tell that magma comes from the mantle
because we can record earthquakes associated with the rising magma that
are down in the upper mantle.
Another way to tell is by the chemical composition of the erupted
products. Through careful analyses it is possible to determine very
precisely the temperature and pressure at which a magma was generated, and
usually also the nature of the source rock that was partially melted to
form the magma. These temperatures and pressures correspond to mantle
depths.
However, it is common for a magma that was generated in the mantle to be
contaminated by material in the crust. When this happens things can get
a little more complicated.
Sincerely,
Scott Rowland
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