page_title: Intrusive rock
hierarchical_section_title: Intrusive rock
caption_attribution_description: Devils Tower National Monument, Wyoming, USA. Taken by Andrew Yool on the 4 September 2003 from a position slightly east of the Monument. Cropped (2400x1800 to 2400x1600 pixels) to 6:4 in Paint Shop Pro 9.01.
context_page_description: Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form intrusions, for example plutons, batholiths, dikes, sills, laccoliths, and volcanic necks. 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 and medium-grained subvolcanic or hypabyssal rock.
context_section_description: Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form intrusions, for example plutons, batholiths, dikes, sills, laccoliths, and volcanic necks. 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 and other plutons) and medium-grained subvolcanic or hypabyssal rock (typically formed higher in the crust in dikes and sills).
caption: Devils Tower, an igneous intrusion exposed when the surrounding softer rock eroded away
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