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

http://www.fi.edu/fellows/payton/rocks/create/igneous.htm

Igneous Rock

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 RockSandstone

Conglomerate

Sedimentary, Clastic RockConglomerate

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 RockHalite

Organic SedimentaryRock

• Form when organic material – sea shells, dead animals and plant material – is compacted and cemented together

• Ex: coquina, coal, anthacite

Coquinaseashellsbymillhill.com

900 × 769 - Made of tiny coquina seashells

http://www.fi.edu/fellows/payton/rocks/create/metamorph.htm

Metamorphic Rock

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

• 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