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Chapter 4 - Chapter Notes
Rock is a solid mixture of crystals of
one or more minerals. Some rocks,
such as coal, are made from organic materials.
The rock cycle is a process by which
one rock type changes to another.
Rocks are classified into sedimentary
rocks, metamorphic rocks, and igneous rocks.
Rocks can be further categorized by
composition. For example,
limestone’s composition is 95% calcite and 5% aragonite.
Deeper in the earth’s crust, it is so
hot that rocks can melt to form magma.
Cooled magma turns back into a solid rock that we call igneous rock.
The igneous rock inside the earth is
intrusive. The igneous rock on the
surface is extrusive. Volcanic
rocks are made from extrusive rocks.
Lava does not always come from
volcanoes. Sometimes it erupts
from long cracks in the Earth’s surface called fissures.
Sedimentary rock is naturally
compacted in layers called strata.
The Grand Canyon contains strata.
Sedimentary rock can come from living
things. Limestone in the sea is
made of the remains of tiny organisms called coral.
Metamorphic rocks are those that have
undergone change from pressure, heat, or both. Foliated metamorphic rock consists of minerals aligned to
look like pages in a book.
Nonfoliated metamorphic rock has no regular pattern.