The Rock Cycle
Igneous-Sedimentary-Metamorphic

Introduction
The rock cycle consists of igneous rocks, sedimentary rocks and metamorphic rocks. These groups of rocks are constantly changing from one group into another. The rocks in each of these families are changing due to tectonic plate movement as crustal plates collide, move apart or slip past each other.

Basalt, Photo by Myrna Martin

Basalt rock that formed in the upper mantle, Myrna Martin

Igneous rocks
Igneous Rocks are a major group of rocks. All igneous rocks develop when molten rock cools and hardens. Find out about these igneous rocks in the links below that form when a volcano erupts: pyroclastic rocks, aa lava, welded tuff, ignimbrite, pyroclastic material, pahoehoe lava and basalt rocks.

Seashells, Photo by Myrna Martin

Seashell collection from shells collected
on Pacific Ocean beaches,
Myrna Martin

Sedimentary rocks
Sedimentary rocks form when older rocks weather. The pieces of older rock are carried down stream to form clastic rocks which include shale, mudstone and siltstone.  Sedimentary rocks found in the rock cycle are varied and include three major groups: clastic rocks, organic rocks and chemical rocks. You will find more information on clastic rocks, organic rocks, limestone caverns, salt domes and coal formation in the links below.

Gneiss, Photo by Myrna Martin

Gneiss rocks are high-grade
metamorphic rocks
, Myrna Martin

Metamorphic rocks
Metamorphic rocks are the third group of rocks. Metamorphic rocks form when igneous, sedimentary and metamorphic rocks recrystallize without melting within the Earth. These rocks form intrusive rocks or plutonic rocks. Limestone rocks that recrystallize into metamorphic rocks form marble. Shale, a clastic rock, can recrystallize into gneiss a high-grade metamorphic rock.

More Rock Cycle Links

Pyroclastic Rocks Find out how pyroclastic rocks form during volcanic eruptions.

Aa Lava Learn more about aa lava flows that occur on the Hawaiian Islands and the lava balls that often form on their surface.

Welded Tuff Find out how welded tuff is produced during violent eruptions and by supervolcanoes.

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


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.

Salt Domes Learn more about how salt domes form, what they are used for and how they are sometimes a key to find oil.

Lava Caves Find out how pahoehoe lava flows form lava caves.

Ignimbrite Learn more about ignimbrite that forms during large volcanic eruptions that produce pyroclastic flows.


Coal Formation Find out how leaves falling into a swamp can turn into coal.

Pahoehoe Lava Find out how pahoehoe lava forms in the Hawaiian Islands.

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.