A chilled margin is a shallow intrusive or

volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates ...

rock texture characterised by a

glassy Glassy is an adjective meaning, of or resembling glass. Glassy may also mean: * Glassy, amorphous metal * ''Glassy'', a 2021 single album, or the title song by Jo Yu-ri * Glassy phase, amorphous solid * Glassy water, amorphous ice * Glassy carbo ...

fine-grained Granularity (also called graininess), the condition of existing in granules or grains, refers to the extent to which a material or system is composed of distinguishable pieces. It can either refer to the extent to which a larger entity is su ...

zone along the margin where the

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natura ...

lava Lava is molten or partially molten rock ( magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or ...

has contacted air, water, or particularly much cooler rock. This is caused by rapid

crystallization Crystallization is the process by which solid forms, where the atoms or molecules are highly organized into a structure known as a crystal. Some ways by which crystals form are precipitating from a solution, freezing, or more rarely de ...

of the melt near the contact with the surrounding low temperature environment. In an intrusive case, the crystallized chilled margin may decrease in size or disappear by later remelting during magma flow, depending on magma

heat flux Heat flux or thermal flux, sometimes also referred to as ''heat flux density'', heat-flow density or ''heat flow rate intensity'' is a flow of energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity ...

. The feature is often seen in dikes or sills, and especially in sheeted dike complexes, where multiple chilled margins are a distinctive feature.

Pillow lava Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava underwater, or ''subaqueous extrusion''. Pillow lavas in volcanic rock are characterized by thick sequences of disconti ...

s often show such chilled margins which are glassy and prove the sudden cooling undergone due to contact with water.

External links

H.E. Huppert and R.S.J. Sparks (1989): Chilled margins in igneous rocks. Earth and Planetary Science Letters, volume 92, issues 3–4, pages 397-405.
Igneous petrology {{petrology-stub