Salangen is a municipality in Troms county, Norway. The administrative centre of the municipality is the village of Sjøvegan, where most of the people in the municipality live. Other villages include Elvenes, Laberget, Salangsverket, and Seljeskogen.
The municipality is situated along the Sagfjorden in south central Troms county. The municipality is mostly coastal areas around the fjord as well as some inland valleys. Salangen is home to the world's northernmost bat population.
Metamorphism is the transformation of existing rock (the protolith) 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.
Various forms of metamorphism exist, including regional, contact, hydrothermal, shock, and dynamic metamorphism. These differ in the characteristic temperatures, pressures, and rate at which they take place and in the extent to which reactive fluids are involved. Metamorphism occurring at increasing pressure and temperature conditions is known as prograde metamorphism, while decreasing temperature and pressure characterize retrograde metamorphism.