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					Types of Rocks

     Mrs. Negrito
  6th Grade Science
      Chapter 16
     Section 1 & 2
                      Rocks
Rock- is a solid mixture of
crystals of one or more
minerals.

Mineral- is naturally
formed solid matter with a
crystal structure.
Rocks are made up of
minerals.
Composition- is the rocks
make-up.
        Rock Classification
Igneous- form when            Granite
hard, liquid rock cools
and hardens.
Sedimentary- form
when rocks are
broken down into
                              Sandstone
smaller pieces that
harden.
Metamorphic- rocks
heated or squeezed.
                               Gneiss
                Texture
Fine-grained rocks made of small grains.

Coarse-grained rocks made of grains that are
larger than a pebble.

Medium- grained texture rocks-between fine and
coarse grained.
                Texture of Rocks




                           Coarse-grained rock
                           Granite




Fine-grained rock
Basalt                           Medium-textured rock
                                 Andesite
              Igneous Rocks
Composition of lava determines type
of rock.
Form when hot, liquid rock, or
magma, cools to form mineral
crystals. Form deep in the Earth or
at sites of volcanic activity.
Extrusive- magma that reaches the
surface and cools forming rocks such
as: pumice,basalt, rhyolite, scoria,
and obsidian,
      Igneous Rocks, cont.
Intrusive- Magma
that cools before
reaching the
surface. The
longer it cools,
the larger the
crystals.
Examples:
Granite,and
gabbro.
          Sedimentary Rock
Form when grains of rock or
sediment collect and harden into
new rock.
Composition of rock depends on the
sediment deposit.
Sediment is cemented together -
Lithification.
Examples: Sandstone, Coquina,
Shale, Rock Gypsum, Limestone,
Coal, Conglomerate, Rock Salt.
         Metamorphic Rocks
Form when rocks
metamorphose or change as
they are heated or squeezed.
The texture depends on how
the minerals are arranged.
Rocks made of different
minerals often are foliated or
banded.
Non- foliated if few different
minerals.
Examples:Marble and Gneiss.
Process that shape the Earth
Weathering- water, ice and heat break
down the rock into smaller pieces or
sediment.
Erosion- when grains of rock are moved
from their source.
Deposition- water, ice, wind or gravity drop
newly formed sediment.
Erosion

				
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posted:9/12/2012
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