The Rock Cycle three Main Families
Igneous. Sedimentary & metamorphic rocks
Three families of rocks
The rock cycle consists of igneous rocks, sedimentary rocks and metamorphic rocks. These three families 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.
Metamorphic rock (left) Sedimentary rock (center) Igneous rock (right)
Igneous Rocks
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Basalt |
Andesite |
Dacite |
Rhyolite |
There are four broad categories of igneous rocks.
Basalt
is 45% to 54% quartz.
Andesite
is 54% to 62% quartz.
Dacite
is 62% to 69% quartz.
Rhyolite
is 69% to 80% quartz.
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
Where and how igneous rocks form
Igneous rocks
Igneous rocks that form during violent
volcanic eruptions are some of the most beautiful and deadliest natural events
on Earth. All igneous rocks were once molten rock that formed during volcanic
eruptions or cooled underground. The amount of quartz in the rock determines
the type of igneous rock that forms.
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Sedimentary Rocks
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Conglomerate |
Petrified wood |
Coquina |
Sedimentary rocks
Sedimentary rocks form when older rocks weather. The pieces of older rock are carried downstream 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.
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Gneiss |
Graphite schist |
Pink marble |
Serpentinite |
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 crystallize into metamorphic rocks form marble. Shale, a clastic rock, can recrystallize into gneiss a high-grade metamorphic rock.
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