A’KF diagram Quick reference
A three-component triangular graph that is used to show how metamorphic *mineral assemblages vary as a function of rock composition within one ...
A-layer Quick reference
The seismic layer corresponding to the *crust of the Earth. It varies in thickness from a few kilometres to 70–90 km. The base lies on the ...
A-subduction Quick reference
The movement of one continental lithospheric *plate under another (*subduction) in a *collision zone, with the separation of part or all of the upper ...
A-tents Quick reference
Raised rock slabs or plates of varying thickness, mostly resulting from the buckling of laminae, plates, and slabs. These forms are generally cracked by tectonic activity, although decreases in lithostatic pressure through unloading, or, more rarely, from surficial expansion of plates caused by intense heat. Smaller plates and slabs may be changed in part through freeze-thaw. A-tents are also known as pop-ups, but ...
A-train Quick reference
A series of Earth-observing satellites operated by NASA and other national space agencies. All the satellites are in *polar orbit...
aa Quick reference
Volcanic **lava rock that is thick and porous and has a rough, jagged surface when it cools. It
Aalenian Quick reference
A *stage in the European Middle *Jurassic (175.6–171.6 Ma, Int. Commission on Stratigraphy, 2004). See also
abandoned channel Quick reference
A former stream channel through which water no longer flows (e.g. a *cut-off).
abandoned well Quick reference
Any *well that has not been used for a long time and/or is not properly sealed, and is so
abandonment facies association Quick reference
A *facies association formed under conditions of rising sea level, when *clastic deposition has ceased and sediment is deposited very slowly....
abapical Quick reference
A directional term meaning away from the shell *apex.
abaptation Quick reference
The process by which an organism is fitted to its environment as a consequence of the characters it inherits, which have been filtered by ...
abatement Quick reference
The elimination or reduction of emissions that create *pollution. Examples include smoke abatement and noise abatement.
abatement debris Quick reference
Waste materials produced by *remediation activities.
Abbey, Edward (1927–89) Quick reference
who wrote the book *Desert Solitaire and is remembered for his strong criticism of public land policies and his
abiogenesis Quick reference
Development of living organisms from non-living matter; as in the supposed origin of life on Earth, or in the concept of spontaneous generation, which was once held to account for the origin of life but which modern understanding of evolutionary processes (...
abiotic Quick reference
Devoid of life, not *biotic, non‐biological. That part of a natural environment that comprises only chemical or physical
abiotic Quick reference
Non-living; devoid of life. Compare
ablation Quick reference
1. The process by which *snow or *ice is lost from a *glacier or *ice cap