Intrusive Rocks

Introduction
Intrusive rocks crystallize and harden beneath the Earth's surface. Some of the rock formations that form are plutons, batholiths, dikes, sills, laccoliths, and volcanic necks.

Mount Rushmore, South Dakota, NPS

Mount Rushmore, South Dakota, NPS

Batholiths
Batholiths are the largest bodies of igneous rocks that form within the Earth. They cover more than 40 square miles on their upper surface. Most batholiths contain several plutons that are solidified magma chambers.

Sierra Nevada Mountains
The Sierra Nevada Mountains are an examples of a large exposed batholith in California. El Capitan and Half Dome in Yosemite National Park are part of the Sierra Nevada Batholith.

Mount Rushmore
Mount Rushmore National Memorial is located in the Harney Peak Granite Batholith in the Black Hills of South Dakota.

Sills
Sills form when molten rock forces its way between layers of older rocks. Sills range from a few centimeters to over a kilometer thick. Dikes form when molten rock cracks through older layers of rock.

Dikes
The molten rock  moves upward toward the Earth's surface because it is lighter than the surrounding rocks. The rocks that form in these cracks are often visible in road cuts as vertical layers of a different colored rock.

More Rock Cycle Links

Clastic Rocks Find out how bits and pieces of older rocks form shale, sandstone and conglomerate rocks.

Pyroclastic Material This page gives all kinds of information about volcanic material that forms during volcanic eruptions.

Organic Rocks Learn how animals extract calcite out of ocean water to form shells that are organic rocks.

Limestone Caverns Learn how limestone caverns form and where you can visit some of them.


Basalt Rocks Basalt rocks cover the floors of all the oceans, create cinder cones and form the largest volcanic mountains on Earth.

Intrusive Rocks Learn more about intrusive rocks that cool underground forming batholiths like the Sierra Nevada Mountains in California.

Rock Cycle Learn more about igneous, sedimentary and metamorphic rocks and how they form.

Kids Fun Science The links on our home page include information about volcanoes, science activities, plate tectonics, the rock cycle and much more.

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