Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form intrusions, such as batholiths, dikes, sills, laccoliths, and volcanic necks.[1][2][3]
Intrusion is one of the two ways igneous rock can form. The other is extrusion, such as a volcanic eruption or similar event. An intrusion is any body of intrusive igneous rock, formed from magma that cools and solidifies within the crust of the planet. In contrast, an extrusion consists of extrusive rock, formed above the surface of the crust.
Some geologists use the term plutonic rock synonymously with intrusive rock, but other geologists subdivide intrusive rock, by crystal size, into coarse-grained plutonic rock (typically formed deeper in the Earth's crust in batholiths or stocks) and medium-grained subvolcanic or hypabyssal rock (typically formed higher in the crust in dikes and sills).[4]
- ^ Intrusive Rocks: Intrusive rocks, accessdate: March 27, 2017.
- ^ Igneous intrusive rocks: Igneous intrusive rocks Archived 2018-05-12 at the Wayback Machine, accessdate: March 27, 2017.
- ^ Britannica.com: intrusive rock | geology | Britannica.com, accessdate: March 27, 2017.
- ^ Philpotts, Anthony R.; Ague, Jay J. (2009). Principles of igneous and metamorphic petrology (2nd ed.). Cambridge, UK: Cambridge University Press. p. 52. ISBN 9780521880060.