Changes included in rocks and minerals when they are subjected to pressures from shock waves travelling at 10–13 km/s resulting from meteorite, cometary, or asteroidal impact. Pressures ranging to more than 5000 kb are experienced during such events. Materials subjected to less than 100 kb are severely disrupted and fractured; between 100 and 250 kb, framework silicates exhibit planar deformation features; maskelynite (vitrified plagioclase feldspar) forms between 250 and 400 kb; quartz and feldspar melt from 400 to 600 kb; while rocks subjected to pressures of more than 600 to 700 kb become molten. Peak pressures are sufficient to vaporize material.
Subjects: Earth Sciences and Geography — Astronomy and Astrophysics.