TThhee CCyycclleelet’s review some basic information …

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Adapted from a Powerpoint by Michigan Department of Environmental QualityAdapted from a Powerpoint by Michigan Department of Environmental QualityGeological Survey Division - http://www.deq.state.mi.us/gsdGeological Survey Division - http://www.deq.state.mi.us/gsd

Natural elements and compounds are minerals.

Rocks are mixtures of minerals.

Rocks make the Earth

Elements combine to make compounds.

SedimentaryRocks

MetamorphicRocks

IgneousRocks

The Earth is made of The Earth is made of 3 kinds of rock that 3 kinds of rock that

are recycled in theare recycled in the RRoocck k CCyyccllee

Igneous RocksIgneous Rocks

Sedimentary RocksSedimentary Rocks

Metamorphic RocksMetamorphic Rocks

Enough about rocks,

on to the cycle …

James Hutton

Developed the Rock Cycle explaining that rocks don’t stay the same forever; natural physical processes cause them to change from one type to another.

weathering

melting

pres

sure

, hea

t

Sedimentary Metamorphic

Igneous

The Rock Cycle.Rocks are neither created nor destroyed, they just

change from one type to another.

The Rock Cycle does not go in

just one direction.

Any given rock can go through any part of the

cycle any number of

times.

http://www.science.ubc.ca/~geol202/rock_cycle/rockcycle.html March 2000

The Earth can be thought of as a giant recycling machine

Google “rock cycle”

Rock cycles

Igneous RocksIgneous Rocks

Igneous RocksIgneous Rocks

Igneous RocksFormed from molten material

Igneous= made from fire• Igneous rocks start

as molten rock or magma which may become solid before ever reaching the surface

• Sometimes magma is full of gases like a pop with the cap on.

• When magma reaches the surface pressure is released, gases begin escaping and it’s lava

Mt. St. Helens Videocam

Igneous Rock• Crystals interlock (grew together )

forming a strong rock. • Magma cools slowly and crystals

have time to grow.• Lava cools quick and the crystals

don’t have time to grow so they’re small or there are none.

• Bigger crystals = slower cooling = deeper

Crystal Size

Rate of cooling determines size of crystals

Fast cooling: no crystals or small crystalsSlow cooling: large crystals

Extrusive: Cool FastNo Crystals

.

Extrusive: Cool Fast

Small Crystals

Examples: Extrusive

• Obsidian

Examples: Extrusive• Pumice

Examples: Extrusive

• Basalt

Intrusive: Cool slowly

• Large crystals

Examples: Intrusive• Granite

Clues it’s Igneous• If crystals are large, the colors

are randomly spread.• If crystals are small, the color is

even and there may be an occasional big crystal

• May have bubbles• May be made of broken

fragments• May be glass.

Sedimentary Starts with Rocks Being Broken into Smaller Pieces

• Heating and cooling causes rock to expand and shrink.

• Water gets into cracks, freezes and expands, splitting the rock.

• Lichens & plants make acids that dissolve rock. Plant roots split rock.

A process called

weathering

Weathered Rock Erodes• Wind, water and gravity,

cause weathered rock to erode

• Eroding fragments of rock get smaller and more rounded the more they erode.

• Faster water can carry bigger fragments, pieces settle out as the current slows and the water deepens. Sediment Deposition

•Sediment Becomes Rock• New layers are always on top of old layers• Sediment builds up and increased weight causes

sediment to compact• Minerals grow between compacted pieces turning

them into rock

Sedimentary RocksSedimentary Rocks

Sed. Rocks often form into layersSed. Rocks often form into layers

From Sediment to Rock• Most sedimentary rocks are formed through a

series of processes: erosion, deposition, compaction, and cementation.

Clues it’s Sedimentary

• Earthy colors (browns, oranges, reds, black, gray, white, clear, sand, mauve, buff, tan, etc.)

• Rounded pieces• Fossils

Metamorphic RocksPressure, heat and fluids cause preexisting materials to becomemetamorphic metamorphic rocks

Metamorphic mountain ranges like the Rockies, Alps and Himalayas are caused by colliding plates

Metamorphism

Himalaya formation

Metamorphic Rock

Metamorphism: Changing of one type of rock to another

by: Heat

Pressure

Chemical reactions

Metamorphism makes rocks stronger or more resistant

Contact Metamorphism

–hot magma pushes through existing rock, heating surrounding rock and changing it to metamorphic.

Classification ofMetamorphic rock

Foliated

&

Non-foliated

Foliated Rocks:• Have visible layers• Mineral grains are flattened and

aligned when pressure is added

PRESSURE

Gneiss has banded foliation

Granite Gneiss

Gneiss

Slate has banded foliation

Shale Slate

Slate

Slate

Non-foliated Rocks:• These DO NOT have layers of

crystals.

Quartzite has no foliation (layers)

Sandstone Quartzite

Quartzite

Marble has no foliation (layers)

Limestone Marble

Marble

• Finished Marble• Unfinished Marble

Clues it’s Metamorphic• Often black and white, or

green.• May be red (garnet) or shiny

(mica)• Often foliated (lines)