| The Rock Cycle
is a group of changes. Igneous rock can change into sedimentary rock
or into metamorphic rock. Sedimentary rock can change into metamorphic
rock or into igneous rock. Metamorphic rock can change into igneous
or sedimentary rock.
rock forms when magma cools and makes crystals. Magma is a hot liquid
made of melted minerals. The minerals can form crystals when they
cool. Igneous rock can form underground, where the magma cools slowly.
Or, igneous rock can form above ground, where the magma cools quickly.
pours out on Earth's surface, magma is called lava. Yes, the same
liquid rock matter that you see coming out of volcanoes.
surface, wind and water can break rock into pieces. They can also
carry rock pieces to another place. Usually, the rock pieces, called
sediments, drop from the wind or water to make a layer. The layer
can be buried under other layers of sediments. After a long time
the sediments can be cemented together to make sedimentary rock.
In this way, igneous rock can become sedimentary rock.
can be heated. But where does the heat come from? Inside Earth there
is heat from pressure (push your hands together very hard and feel
the heat). There is heat from friction (rub your hands together
and feel the heat). There is also heat from radioactive decay (the
process that gives us nuclear power plants that make electricity).
does the heat do to the rock? It bakes the rock.
does not melt, but it does change. It forms crystals. If it has
crystals already, it forms larger crystals. Because this rock changes,
it is called metamorphic. Remember that a caterpillar changes to
become a butterfly. That change is called metamorphosis. Metamorphosis
can occur in rock when they are heated to 300 to 700 degrees Celsius.
tectonic plates move around, they produce heat. When they collide,
they build mountains and metamorphose (met-ah-MORE-foes) the rock.
rock cycle continues. Mountains made of
metamorphic rocks can be broken up and
washed away by streams. New sediments
from these mountains can make new sedimentary
rock cycle never stops.