Glossary :: I

Ice Age

An extended period of time where there is extensive glaciation covering the Earth

Inbreeding coefficient (F)

The probability that an individual taken at random from the population will be autozygous.

Inbreeding depression

Reduction, in inbred individuals, of the mean value of a character (usually one correlated with fitness).

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

That has crystallised beneath the surface.

Isolating mechanism

A genetic difference between populations that prevents or restricts gene flow between them. See reproductive isolation.

Isostacy

The study of the responses of the Earth to loads (mountain belts, glaciers) placed on it. Isostatic theory states that at the depth of compensation all pressures exerted by rocks above are equal. Northern Europe is currently re-bounding from glaciers that...More

Isostatic sea level change

Sea level change on a local scale. Can be caused by glaciers making continents sink or melting glaciers making the continents rise again (isostatic rebound) or local tectonic activity. Combined with the eustatic changes make a relative sea level change....More

Isotropic

A mineral that is isotropic is one that appears black in thin section in both plane and polarised light.

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