GeologyRocks

Ecologite

A metamorphic rock of mantle origin. It is usually composed of garnet and omphacite (a pyroxene).

Enthalpy

A measure of internal energy of a system. For a gas:

H=E+pV

Where H is the enthalpy, E is the internal energy, p is the pressure and V is the volume.

Entropy

In thermodynamics entropy is the amount of energy not available to do work.

Eustatic Sea Level Change

Sea level change on a global scale. Causes include the switching between ice age and interglacial periods and changes in the global ocean volume due to plate tectonic movement. Combined with the isostatic changes make a relative sea level change.

Evaporite

A chemical sediment or sedimentary rock that forms by precipitation from evaporating waters. Gypsum, halite, nitrates and borates are examples of evaporite minerals. The minerals precipitate out in reverse order of their solubility. For sea water this is:

1. Calcite (CaCO₃) and dolomite (CaMg(CO₃)₂)
2. Gypsum (CaSO₄-2H₂O) and anhydrite (CaSO₄).
3. Halite (i.e. common salt, NaCl)
4. Potassium and magnesium salts (sometimes referred to as Bittern Salts)