Rocks
•A solid material made
up of 1 or more
minerals, or other
things – including the
remains of once-living
things.
•Earth’s rocks are made
up of about 20
minerals.
A rock can have several
minerals or only one.
Classify Rocks
• Color: color of rock depends on
the minerals that make it up.
• Texture: size, shape,
arrangement of the grains
Large grains – coarse texture
Small grains – fine texture
• Composition: The minerals
the rock is made up of
–Easier to ID course grained
rocks
• How/where rocks are
formed -
Classify Rocks
3 Major groups:
Igneous
Sedimentary
Metamorphic
3 Main Types of Rocks
Igneous Rock
http://www.fi.edu/fellows/payton/rocks/create/igneous.htm
Igneous Rock
• Fire formed
• Forms when magma or lava
cools and hardens
–Intrusive
–Extrusive
Intrusive Igneous Rock
• Cools and hardens beneath the
surface.
• Coarse grained. Larger mineral
crystals.
• Forms much Continental Crust.
• Ex: Granite, diorite, pegmatite
Extrusive Igneous Rock
• Forms from Lava on the
surface of the Earth.
• Fine-grained. Small Crystals
Cool quickly – Basalt most
common Makes up the oceanic
crust.
• Ex: Obsidian, pumice, andesite
Granite - Intrusive
Obsidian - extrusive
Sedimentary Rock
http://www.fi.edu/fellows/payton/rocks/create/sediment.htm
Sedimentary Rock
• Form in places where there was
once water
• Form from sediment that is
compacted and cemented
together
• Takes millions of years to form
Sediments
• Particles of rock, minerals or
organic material.
• Sand, gravel, seashells, leaves,
dead plants & animals.
• Weathering - The chemical
and physical processes that
break down rock at Earth’s
surface.
• Erosion: wind, water, gravity
carries sediments to a new
place.
Deposition: when the water stops
moving and “drops off” the
sediments
Compaction: slowly the layers of
sediment press down on top of
other layers
.
Cementation: when the
layers are “stuck” together.
Water evaporates, leaving
minerals behind which glue
the sediments together
3 Types of Sedimentary
Rock
Clastic Rock: Made up of
particles of pre-existing rock
Can form from igneous,
metamorphic or other
sedimentary rocks
Ex: sandstone, conglomerate
Sandstone
Sedimentary, Clastic Rock
Sandstone
Sedimentary, Clastic Rock
Conglomerate
Conglomerate
Chemical Sedimentary Rock
• Form due to chemical reaction –
Evaporites
http://geology.campus.ad.csulb.edu/people/bperry/Sedimentary%20Rocks%20Tour/chemical_sedimentary_rocks.htm
• Can occur in oceans, lakes, caves
and hot springs.
• Ex: limestone, halite, calcite
Limestone found in Arizona –
Once part of a reef under water
Sedimentary, Chemical Rock
Halite
Organic SedimentaryRock
• Form when organic material
– sea shells, dead animals
and plant material – is
compacted and cemented
together
• Ex: coquina, coal, anthacite
Coquina
seashellsbymillhill.com
900 × 769 - Made of tiny coquina seashells
Metamorphic Rock
http://www.fi.edu/fellows/payton/rocks/create/metamorph.htm
Metamorphic Rock
• Meta – Change
• Morph - form
• Original rock – igneous,
sedimentary, metamorphic – is
changed by intense heat and
pressure causing physical or
chemical changes
Metamorphic Rock
• Can form when:
–rock is deep within earth’s surface –
subjected to high temps and
pressure of layers above
–Tectonic processes – continental
plates colliding
–Rock is heated by molten magma
nearby
Metamorphic Rock
• One type of rock is changed
into another type of rock
• Igneous granite is changed
into metamorphic gneiss
• Sedimentary rock sandstone
changes into quartzite
Metamorphic Rock
• 2 Types: foliated and non-foliated
–Foliated- banded
• Examples - Gneiss, schist,
slate
–Non-foliated – not banded
• Examples – marble, quartzite
Gneiss - foliated
Schist - foliated
Marble – non-foliated
Quartzite – non-foliated
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What type of rock do I have
http://www.minsocam.org/MSA/K12/rkcycle/typeofrock.html
Rock cycle real pix and describe steps
http://www.open2.net/geologytoolkit/rockcycle_embedded.html
Good click and drag animation
http://www.kscience.co.uk/animations/rock_cycle.htm
• Pictures of Different Rocks – Rock Picture Gallery
• http://geology.about.com/library/bl/images/blrockindex.htm