In geology, a dyke (or dike) is a sheet or layer of extraneous rock that runs through a pre-existing rock body. Dykes occur in both igneous and sedimentary rock bodies and usually come about by injection of magma into cracks, fractures or bedding planes in the older host rock. The example here shows a quarzitic dyke in a migmatitic host rock.

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Photo credit: © DIRK WIERSMA/SCIENCE PHOTO LIBRARY / Alamy / Afripics
License: Licensed
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Keywords: -, bedding, crack, cracks, dike, dyke, earth, extraneous, fracture, geological, geology, host, igneous, injection, metamorphic, migmatite, migmatitic, plane, pre-existing, quartz, quarzitic, rock, sciences