A melt, generally containing suspended crystals and other volatiles, formed by total or partial melting of solid mantle or crustal material.

The layer beneath the crust, but above the core in the interior of the Earth. It's composition is broadly that of ultrabasic rocks.

Area of dark basaltic lava on the Moon (pl. Maria).

A division of a formation, generally of distinct lithologic character and of only local extent.

Era comprising the Triassic, Jurassic and Cretaceous, spanning 245-65Ma.

Metamorphosis require heat, pressure and time and is an extension of lithification, but it can occur on any rocks type (including metamorphic rocks). There is a continuum of type from heat dominated (marble) to pressure dominated (blueschist). Metamorphism is ranked in terms of a grade. A high grade metamorphic rock is a gneiss, which has undergone intense heat and pressure. It is important to note metamorphism occurs in the solid state - there is no melting. If the rock starts to melt it is called a migmatite (Mixed IGneous and metamorphic rock).

Micro-crystalline carbonate mud.

A naturally occurring homogeneous solid with a highly ordered lattice and of a defined chemical composition.

See Mohorovičić discontinuity.

The Mohorovičić discontinuity, usually referred to as the Moho, is the boundary between the Earth's crust and the mantle. The Moho serves to separate both oceanic crust and continental crust from underlying mantle. The Mohorovičić discontinuity was first identified in 1909 by Andrija Mohorovičić, a Croatian seismologist, when he observed the abrupt increase in the velocity of earthquake waves (specifically P-waves) at this point.