Rocks
Rocks
Mixture of two or more different
minerals that have been:
cemented together
squeezed and heated together
melted and cooled together
The Rock Cycle

The diagram of the rock cycle shows how
rocks change slowly over time.
Types of Rocks
1. Igneous
2. Metamorphic
3. Sedimentary
1. Igneous Rocks
“Igneous” comes from Latin for “fire”

Most igneous rocks are produced deep
underground by the cooling and hardening
of magma (melted rock).
Formation of Igneous Rocks
A. Intrusive Rocks- form from
magma that cools below the surface
of the earth. Ex. Granite
B. Extrusive Rocks- form as lava
cools on the surface of the earth.
Ex. Obsidian
Examples: Formation of Igneous
Rock

-Extrusive- Formed from lava; volcanic
Obsidian

Pumice
Intrusive- Formed deep within the earth
Granite
Textures of Igneous Rock
1. Glassy
2. Coarse-grained
Obsidian
Granite
3. Fine-grained
Basalt
2. Metamorphic Rocks

Formed from heat and pressure changing
the original or parent rock into a
completely new rock. The parent rock can
be either sedimentary, igneous, or even
another metamorphic rock.
Classifying Metamorphic Rocks
1. Foliated- when mineral grains
flatten and line up in parallel
layers.
2. Unfoliated-when mineral grains
grow and rearrange but do not
form layers.
Foliated
Gneiss
Unfoliated
Marble
3. Sedimentary Rocks
Form when sediments are pressed
and cemented together, or when
minerals form from solutions.
 Usually consist of layers

Classification of Sedimentary
Rocks
1. Detrital Sed. Rocks- (Clastic Rocks)Made of the broken fragments of other
rocks.
A. Weathering- the process of breaking
rocks into smaller pieces. Happens when
rock is exposed to air, water, or ice.
B. Erosion- the movement of weathered
material.
C. Compaction- when the sediments
stick together and form solid rock.
D. Cementation- when large sediments
are held together by natural cements that
are produced when water soaks through
rock and soil.
E. Shape & Size1. Conglomerate- when the
sediments are rounded
2. Breccia- when the sediments
have sharp angles.
Clastic Rocks

Conglomerate

1. Sandstone

2. Mudstone
2. Chemical Sed. Rocks- Formed
when dissolved material comes out of
solution by inorganic processes such as
evaporation.
Examples are
1. Limestone
and
2. Rock Salt
3.
Organic Sedimentary RocksRocks made from the remains of
once-living things
Coquina
Organic Sed. Rock Examples
Fact about the Mississippi River
Did You Know?


The Mississippi River carries an average of
436,000 tons of sediment each day
It moves an average of 159,000,000 tons
of sediment a year
Distribution of Rocks in the U.S.