GeologyRocks

Aa

A solidified lava flow with a blocky surface, formed from a viscous lava. The name is of Hawaiian origin.

Agpaitic

Alkaline rocks having the alkalis over Al ratio in excess of 1, and containing a suite of complex alkali titano-, niobo- and zirconosilicates (e.g. eudialyte).

Alkaline

When applied to igneous rocks, this word implies the presence of Sodium (Na) and/or Potassium (K).

Columnar jointing

Vertical columnar jointing forms as a result of cooling, particularly of lava. The joint systems associated with cooling are typically polygonal in nature due to the cooling introducing stresses that are isotropic in the plane of the layer. A good example of columnar jointing can be see at Giant's Causeway in Ireland.

Cumulate Rocks

Formed from the settling of crystals within a magma chamber, may be layered if dense minerals are allowed to sink preferentially.

Fissure Eruption

An eruption occurring through long, open crack in the ground. They commonly form flood basalts which are repeated flows on low viscosity lava and can cover large areas.

Gardar Province

Geological area of south-west Greenland famous for its alkali intrusions especially Ilimaussaq which has over 200 minerals associated.

Definition provided by: Tim Ivanic (University of Edinburgh)

Incompatible Elements

Incompatible relative to mantle minerals; those elements with large ionic radii such as Nb, Zr, U, Th, K, Na, Li, Be, REE, that preferentially go into the melt rather than remain in residual minerals.

Intrusion Magma

Magma that has crystallised beneath the surface.

Definition provided by: Tim Ivanic (University of Edinburgh)

Lahar

A mudflow associated with volcanic eruptions when volcanic ash mixes with water.