Understanding Rocks
A self guided tour
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Earth and sky, woods and fields, lakes
and rivers, the mountain and the sea,
are excellent schoolmasters, and teach
some of us more than we can ever
learn from books.
John Lubbock
Credits
Start the tour
About The Teacher
Mr. Stephens
Employer: Brandywine Heights Area School
District
Address: 200 W Weiss St. Topton PA.
19562
Email: benste@bhasd.org
Job Title: 8th Grade Earth/Space Science
Teacher
Phone: (610) 682-5131
Hours of Work: 7:30am until 3:00 pm
Self portrait
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The Rock Cycle
The process by which one rock type changes into
another. Each rock is classified by texture,
composition and color.
Metamorphic
Sedimentary
Igneous
Additional info
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Credits
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Background slide one http://www.alaska-in-pictures.com/data/media/22/lava-rockformations_8244.jpg
Credit button http://www.dieuestam0ur.com/credits-button.jpg
Home button
http://1.bp.blogspot.com/_9raJS75Kbcs/R71qLjn7HvI/AAAAAAAABP4/RnVLRUJ1hKg/s320/phot
oshop-website-home-button-icon36-thumb.gif
The Rock Cycle http://www.unificationtheory.com/images/Rock-Cycle.jpg
Additional Info slide 4 http://cd7.e2bn.net/e2bn/leas/c99/schools/cd7/website/BluePlanet.htm
Igneous rock slide 4
http://www.scarborough.k12.me.us/wis/teachers/dtewhey/webquest/nature/images/lava_flow.
jpg
Metamorphic rock slide 4
http://www.americansouthwest.net/arizona/photographs700/bwrocks.jpg
Sedimentary rock slide 4 http://eqdoc.home.netcom.com/sltinclinedrx.jpg
Sedimentary rock formation slide 5 http://geoscape.nrcan.gc.ca/nsask/images/rocks1_e.jpg
Igneous Formation slide 7 http://www.revisionworld.com/files/igneous.jpg
Granite slide 9
http://www.historyforkids.org/scienceforkids/geology/rocks/igneous/pictures/granite2.jpg
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Additional Credits
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Diorite http://www.bgsd.k12.wa.us/hml/jr_cam/science/rocks/%20web_rocks/diorite.jpg
Granite samples http://www.stonemastersofidaho.com/images/Granite-main.jpg
Rhyolite http://www.swisseduc.ch/stromboli/glossary/icons/rhyolite.jpg
Basalt http://www.basalt.com.au/_borders/Basalt.jpg
Andesite http://www.otago.ac.nz/geology/research/general_geology/rocksminerals/images/andesite.jpg
Fine grained siltstone http://gsc.nrcan.gc.ca/mindep/photolib/gold/nugget/images/fig24.jpg
Sandstone http://depthome.brooklyn.cuny.edu/geology/core332/images/sanstone.jpg
Temperature and pressure graph http://comp.uark.edu/~sboss/study302.jpg
Contact metamorphism drawing http://nature.berkeley.edu/classes/eps2//wisc/jpeg/metam.jpg
Contact metamorphism image http://z.about.com/d/geology/1/0/9/S/contactmetamorph.jpg
Cliff erosion http://gallery.nen.gov.uk/gallery_images/0805/0000/0276/100_0157_mid.jpg
Deposition http://www.belmont.sd62.bc.ca/teacher/geology12/photos/erosionwater/deposition-sediments.jpg
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Sedimentary Rocks
Rocks that form when sediments are
compacted and cemented together.
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Sedimentary rock Formation
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Grains of sand and sediment eroded by
weathering
Form thick layers that are eventually cemented
together
Commonly formed on the ocean floor and other
low areas
The most common rock found on the Earth’s
surface
http://www.youtube.com/watch?v=Etu9BWbuDlY
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Weathering
Notice the erosion
taking place on
the face of the
cliff. The material
collecting on the
beach will
eventually turn
into a sedimentary
rock.
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Deposition
Eroded materials that
are carried by water
are eventually
deposited in ponds,
lakes or oceans.
Particles are
deposited according
to size.
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Texture
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The texture is determined by the size and
shapes of the rock’s grains
 Fine grained – silt or clay particles
 Medium Grained – sand
 Coarse Grained – pebbles
Fine grained
Fine grained siltstone
Notice how
difficult it is to
see each mineral
particle. In fine
grained rocks
the gains are
tightly packed
together.
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Medium Grained
Sandstone
If you look
closely you can
see the different
rock grains that
make up this
rock.
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Coarse Grained
Bits and pieces of
pebbles and rocks
naturally cemented
together. Notice
how much larger
the particles are
compared to the
medium and fine
grained samples.
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Coarse grained conglomerate
Clastic Sedimentary Rocks
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Rock fragments are compacted and
cemented together
Classified according to grain size
Coarse-grained to fine-grained
Pebbles, sand, silt and clay
Conglomerate
Sandstone
Siltstone
Shale
Chemical Sedimentary Rocks
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Form from solutions of minerals in water
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Minerals can precipitate out of water solution
Limestone
Dolomite
Chert
Rock Salt
Organic Sedimentary Rocks
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Formed by the accumulation of organic
debris
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Coal
Plant and animal material
Coquina
Chalk
Metamorphic Rocks
Rocks that forms
when the texture and
composition of a
preexisting rock
changes by heat and
pressure produced
deep within the Earth
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http://www.youtube.com/watch?v=1oQ1J0w3x0o
Metamorphic Rocks cont.
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Metamorphic rocks are formed deep within the
Earth
“Meta” in Latin means change
“Morph” in Latin means shape
Thus, metamorphic means a physical change
due to heat and pressure.
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Contact Metamorphism
When surrounding
rock comes in contact
with magma but do
not melt they often
change to harder
metamorphic type
rocks.
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More contact metamorphism
The lava flow at the
top of the picture
has baked the mud
beneath it into brickred shale. This is an
ideal case of contact
metamorphism.
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Regional Metamorphism
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Regional metamorphic
rocks are rocks that are
altered in composition and
texture due to:
 extreme heat and
pressure over a large
area
 during mountain
formations or
subduction
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Heat and Pressure Relationship
As temperature
increases less
pressure is
needed.
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As pressure
increases less
temperature
is needed.
Igneous Rocks
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Rocks that form
from cooling of
magma and lava
both inside and on
the surface of the
Earth.
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Introduction to Igneous Rocks Video Clip
Igneous Rocks
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Igneous comes from the Latin word for “fire”
 Intrusive – forms when magma cools
below the Earth’s surface
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Extrusive – forms from lava cooling on the
surface of the Earth
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Intrusive
• Intrusive igneous rocks form when magma
cools slowly below the Earth's surface.
•Most intrusive rocks have large, well-formed
crystals.
• Examples include granite, gabbro, and
diorite. Notice how each sample has large
crystals that are easily seen.
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Extrusive
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Extrusive igneous rocks form when magma
reaches the Earth's surface cooling quickly to
form lava.
Most extrusive (volcanic) rocks have small
crystals.
Examples include basalt, rhyolite, and andesite.
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Basalt
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Rhyolite
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Andesite
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Composition
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The minerals a rock is made of determines its
composition.
 Example – Granite typically has 10% Biotitie
Mica, 35% Quartz and 55% Feldspar.
 Different classifications of Granites can have
different amounts of each of these minerals.
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Composition cont.
Colors often vary due to impurities found within the
rock. Below is good example of color variations.
Notice: each
sample varies but
they are all part
of the same
(granite) family of
rocks.
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Mafic Rocks
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Rocks which are relatively high in heavier
elements
Mafic minerals are usually dark in color
The term is derived from
 MA from magnesium
 FIC from the Latin word for iron
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Felsic Rocks
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Felsic rocks have low percentage of heavier
elements
Felsic rocks are light in color
Higher percentage in lighter elements such as
silica and oxygen
The term comes from
 FEL for feldspar
 SIC which indicates the higher percentage of
silica
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Granite
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Gabbro
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Diorite
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Coal Video Clip:
http://www.delawareandlehigh.org/talesofth
etowpath/Bookshelf/Coal/
Limestone Video Clip:
http://www.delawareandlehigh.org/talesofth
etowpath/Bookshelf/Limestone/
Slate Video Clip:
http://www.delawareandlehigh.org/talesofth
etowpath/Bookshelf/Slate/