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Köppen system

A commonly used system of climate categorization developed by Russian climatologist Wladimir Köppen. It is based on the kinds of vegetation that areas sustain, and defines 12 climate types: rainforest, monsoon, tropical savanna, humid subtropical, humid continental, oceanic, Mediterranean, steppe, subarctic, tundra, polar ice cap, and desert. Updated by Rudolf Geiger, it has been refined to five groups each with two to four subgroups.


An irregularly shaped mound made up of sediment that accumulated in a depression on a retreating glacier. The mound-like deposits of sorted sediment are then deposited on the land after the glacier retreats.


A silicate clay mineral, also known as "china clay." Kaolinite is the main ingredient in fine china dishes such as Wedgwood.

karst topography

A kind of landscape defined by bedrock that has been weathered by dissolution in water, forming features like sinkholes, caves, and cliffs.
Karst topography primarily forms in limestone bedrock.


A depression formed where a large, isolated block of ice became separated from the retreating ice sheet. The ice becomes buried by sediment; when it melts, it leaves a shallow depression in the landscape that often persists as a small lake.

kinetic energy

The energy of a body in motion (e.g., via friction).


Mafic volcanic rocks richer in magnesium and erupted at a higher temperature than basalts. They are restricted to the Archean, when the mantle temperatures were higher at the depths where magma is generated. Komatiites often exhibit “spinifex texture,” an unusual crystallization-cooling texture that produces large, long crystals.


A silicate mineral, one of several phases in the aluminum silicate (Al2SiO5) system.


Pyrophyllite, kyanite, and sillimanite form a metamorphic progression of aluminum silicate minerals formed at increasingly higher temperature and pressure. Andalusite forms at high temperatures but low pressures. All of these minerals form mullite when heated to very high temperatures. Mullite is used in manufacturing glass and ceramics that can withstand very high temperatures.


See also metamorphism, mineral.


The kyanite family of minerals includes kyanite, sillimanite, pyrophyllite, and andalusite. All have the same chemical formula and are polymorphs (minerals with the same composition but different crystal structures). These different crystal structures form under different conditions of heat and pressure, and reflect the geologic history and degree of metamorphism of the rocks in which they are found.