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....