The importance of xenoliths

Xenoliths are one of the most important pieces of rock to come from volcanoes. They are fragments of material which are not part of an area of molten/solidified magma within a magma chamber or conduit. The area xenoliths come from is also known as the country rock. Xenoliths are important because of where they come from, they give us an insight into the rocks present deep into the Earth's interior and into those at shallower levels as well. Common xenoliths can include the rock basin underneath a volcano, to crystals sourced from the mantle - such as the green olivine and the black pyroxene.

The picture below gives an example of a sedimentary xenolith found in a 2001 lava flow on Mt. Etna. It is from the base of Mt. Etna and tells us something about where the magma came from and whether it was part of the central conduit system or not. In this case the magma is from an eccentric eruption which rose quickly, enabling xenoliths to be present.