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Metamorphic rocks are formed by subjecting any rock type—sedimentary rock, igneous rock or another older metamorphic rock—to different temperature and pressure conditions than those in which the original rock was formed. This process is called metamorphism, meaning to "change in form". The result is a profound change in physical properties ...
A facies encompasses all the characteristics of a rock including its chemical, physical, and biological features that distinguish it from adjacent rock. [ 2 ] The term "facies" was introduced by the Swiss geologist Amanz Gressly in 1838 and was part of his significant contribution to the foundations of modern stratigraphy , [ 3 ] which replaced ...
Slate – Metamorphic rock - A low grade metamorphic rock formed from shale or silts; Suevite – Rock consisting partly of melted material formed during an impact event – A rock formed by partial melting during a meteorite impact; Talc carbonate – A metamorphosed ultramafic rock with talc as an essential constituent; similar to a serpentinite
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.
This process is known as lithification. Igneous rocks have crystallised from a melt or magma. The melt is made up of various components of pre-existing rocks which have been subjected to melting either at subduction zones or within the Earth's mantle. The melt is hot and so passes upward through cooler country rock. As it moves, it cools and ...
Solidified lava flow in Hawaii Sedimentary layers in Badlands National Park, South Dakota Metamorphic rock, Nunavut, Canada. Geology (from Ancient Greek γῆ (gê) 'earth' and λoγία () 'study of, discourse') [1] [2] is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. [3]
Micas (/ ˈ m aɪ k ə z / MY-kəz) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates. This characteristic is described as perfect basal cleavage. Mica is common in igneous and metamorphic rock and is occasionally found as small flakes in ...
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. [ 1 ] [ 2 ] Rock that contains greater than 75% ash is considered tuff, while rock containing 25% to 75% ash is described as tuffaceous (for example, tuffaceous sandstone ). [ 3 ]