Shock metamorphism or impact metamorphism describes the effects of shock-wave related deformation and heating during impact events.
Shocked quartz with two sets of ‘decorated’ planar deformation features in impact melt rock from the Suvasvesi South impact structure, Finland (thin section photomicrograph, plane polarized light).
Shatter cones developed in fine grained dolomite from the Wells Creek crater, USA.
Metamorphism is the transformation of existing rock to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of 150 °C (300 °F), and often also at elevated pressure or in the presence of chemically active fluids, but the rock remains mostly solid during the transformation. Metamorphism is distinct from weathering or diagenesis, which are changes that take place at or just beneath Earth's surface.
A cross-polarized thin section image of a garnet-mica-schist from Salangen, Norway showing the strong strain fabric of schists. The black crystal is garnet, the pink-orange-yellow colored strands are muscovite mica, and the brown crystals are biotite mica. The grey and white crystals are quartz and (limited) feldspar.
Amphibolite formed by metamorphism of basalt showing coarse texture
A mylonite (through a petrographic microscope)
A metamorphic rock, deformed during the Variscan orogeny, at Vall de Cardós, Lérida, Spain
