Post on 17-Jan-2016
TThhee CCyycclleelet’s review some basic information …
TThhee RRoocckkTThhe e RRoocck k CCyyccllee
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 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
.
Examples: Extrusive
• Obsidian
Examples: Extrusive
• Basalt
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)