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-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.