A vocabulary of landscape — a landscape of words
1467 entries
xenolith
A xenolith is a fragment of one rock caught inside another: a piece torn from the wall of a magma chamber or a conduit, engulfed, and frozen in place when the magma cooled. It sits in the host rock as a dark angular inclusion with a sharp margin, sometimes partly melted around the edge, and it’s older than everything around it.
Etymology
The word is Greek for foreign stone. It belongs to a small family built the same way, including xenocryst for a single foreign crystal and xenon, the element, named for being a stranger among gases.
Notes
Xenoliths are how the deep earth is sampled. Some volcanic pipes rise fast enough to carry pieces of the mantle to the surface intact, and those fragments are the only direct samples of rock from tens of miles down.