# Chilled margin

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A **chilled margin** is a shallow [intrusive](/source/Igneous_intrusion) or [volcanic](/source/Extrusive_rock) [rock](/source/Rock_(geology)) texture characterised by a [glassy](/source/Volcanic_glass) or [fine-grained](/source/Granularity) zone along the margin where the [magma](/source/Magma) or [lava](/source/Lava) has contacted air, water, or particularly much cooler rock. This is caused by rapid solidification 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](/source/Heat_flux).

The feature is often seen in [dikes](/source/Dike_(geology)) or [sills](/source/Sill_(geology)), and especially in [sheeted dike complexes](/source/Sheeted_dike_complex), where multiple chilled margins are a distinctive feature.

[Pillow lavas](/source/Pillow_lava) 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.](https://dx.doi.org/10.1016/0012-821X(89)90063-0)

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Adapted from the Wikipedia article [Chilled margin](https://en.wikipedia.org/wiki/Chilled_margin) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Chilled_margin?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.