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ROCKS
Brian Madison: You remember that
spelling bee you won in the 1st grade?
Billy Madison: Oh no, you didn't.
Brian Madison: Rock? "r-o-k"?
Billy Madison: Yea, so what's your
point?
Brian Madison: r-o-C-k!
Billy Madison: Ohh! The "C" is silent.
IGNEOUS ROCKS:
forms when magma cools
crystals form during cooling
Two types of
Igneous Rocks
1. Intrusive
2. Extrusive
Intrusive
 Magma cools SLOWLY below Earth’s
Surface
 LARGE visible crystals
 Large crystals have time to form because
the cooling process is slow because it is
very warm closer to the mantle
Intrusive Igneous: Granite
Where would intrusive
igneous rock likely be found?
 Inside or below a volcano
 In the mantle
Extrusive
 Magma cools RAPIDLY above Earth’s
surface
 Has SMALL microscopic crystals
 Crystals do not have time to form (because
cooling happens very quickly) so they’re
very small
Extrusive
Igneous:
Basalt
Where would extrusive
igneous rock likely be found?
 Outside of a volcano
 In ridges!
SEDIMENTARY ROCKS
 Form when old
pieces of rocks
have been
weathered and
combined to
make a new
rock
Sedimentary Rocks
 Formed via 4 step process:
 1. Weathering—wind, rain, and chemicals
decompose the rocks
 2. Erosion—Pieces of rock moved by wind or water
 3. Deposition—Pieces dropped in new location
 4. Sedimentation—Pieces compressed and
cemented together
 So, sedimentary rocks are formed where
weathering occurs!
 On the surface of the earth and near water
Sedimentary Rocks:
Imp Point
 As sediments continue to stack on top of
each other, LAYERS will be formed in the
rock
 Therefore, sedimentary rocks contained
LAYERS called strata
Layers of Sedimentary Rock
 The layers that were deposited first will be on
the bottom.
 So, oldest layers of rock are on the bottom
and the newest layers of rock are on the top
 Layers of rock can be dated and can tell us a
lot of information about the conditions and the
species the lived when that rock was deposited
 Fossils are often found in layers of sedimentary rock
This picture
shows
layers of
rock on
earth. You
can see that
the deepest
layers
contain the
oldest
fossils
Which layer
here is the
oldest? The
newest?
Answer:
 Kaibab
Formation is
oldest
 Dakota
Formation is
newest
Rock Layers of
the Grand Canyon
Sedimentary Rocks
 Sandstone
Sedimentary Rock
 Limestone
Sedimentary Rock
 siltstone
Metamorphic Rocks
 Created when other rocks (sedimentary
or igneous) are changed by heat and
pressure
 Found at / near subduction zones
because this is where crust (rock) is
pushed downward to areas of heat and
pressure!
METAMORPHIC ROCKS
Metamorphic Rocks
 Quartzite
Metamorphic Rocks
 Marble
VIDEO
 http://player.discoveryeducation.com/inde
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