Three Types of Rocks
Environmental Science
Name: ___________________________________________________ Period: ____ Date: _________
Essential Question: How are rocks classified?
Igneous Rocks
Igneous rocks are crystalline solids which form directly from the cooling of lava ( extrusive) and magma
(intrusive). This is an exothermic process (it loses heat) and involves a phase change from the liquid to
the solid state. The earth is made of igneous rock - at least at the surface where our planet is exposed to
the coldness of space. Igneous rocks are given names based upon two things: composition (what they
are made of) and texture (how big the crystals are). There are two types of igneous rocks- extrusive
igneous rocks have small crystals and intrusive igneous rocks have big crystals because the crystals had
time to grow due to the slow cooling of the rock.
Sedimentary Rocks
In most places on the surface, the igneous rocks which make up the majority of the crust are covered by
a thin veneer of loose sediment, and the rock which is made as layers of this debris get compacted and
cemented together. Sedimentary rocks are called secondary, because they are often the result of the
accumulation of small pieces broken off of pre-existing rocks. There are three main types of sedimentary
rocks:
Clastic: your basic sedimentary rock. Clastic sedimentary rocks are accumulations of clasts: little pieces
of broken up rock which have piled up and been "lithified" by compaction and cementation.
Chemical: many of these form when standing water evaporates, leaving dissolved minerals behind.
These are very common in arid lands, where seasonal "playa lakes" occur in closed depressions. Thick
deposits of salt and gypsum can form due to repeated flooding and evaporation over long periods of
time.
Organic: any accumulation of sedimentary debris caused by organic processes. Many animals use
calcium for shells, bones, and teeth. These bits of calcium can pile up on the seafloor and accumulate
into a thick enough layer to form an "organic" sedimentary rock.
Metamorphic Rocks
Any type of Rock can become a metamorphic rock.
Metamorphic rocks form deep in the earth where
high temperature, great pressure, and chemical
reactions cause one type of rock to change into
another type of rock. Metamorphic rocks begin to
form at 12-16 kilometers beneath the earth's
surface. They begin changing at temperatures of
100 degrees Celsius to 800 degrees Celsius. If you
squeeze and heat a rock for a few million years, it
can turn into a new kind of rock.
http://jersey.uoregon.edu/~mstrick/AskGeoMan/geoQuerry13.html
Clarifying Questions:
1. What are the three basic types of rocks?
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2. How do igneous rocks form?
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3. What does it mean by exothermic process? Think!
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4. What is the surface of the Earth made of?
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5. How are igneous rock named?
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6. How do sedimentary rocks form?
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7. How are extrusive igneous rocks different from intrusive igneous rocks?
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8. Why are sedimentary rocks called secondary?
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9. What are the three types of sedimentary rocks?
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10. How do clastic rocks, a type of sedimentary rock, form?
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11. What kind of sedimentary rock is one with shell?
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12. What kind of rock can become a metamorphic rock?
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13. How do metamorphic rocks form?
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Metamorphism – rocks change due to extreme heat and pressure.
Sedimentary rock
sandstone
15.
limestone
Metamorphic rock
14.
slate
16.