Rock Cycle

1
Rock Cycle

• Details and definitions

2
The Rock Cycle

• Goals
• Important to understanding
• The ever-changing earth
• The reasons for stream sediments and ocean
  beaches
• Without a rock cycle there would be no mountains
• Land would be flat, eroded away by wind and water
• Rivers would be full of sediments and meandering
• Nutrients from the rocks would be trapped in the
  sediments never to be returned to organisms

3
The Rock Cycle
To understand rock cycle we need to understand
water cycle and plate tectonics as they directly
influence what happens
Plate Tectonics
Water Cycle
Rock Cycle
Mountain building
Weathering and Erosion
Tectonics process constantly recycles rock
4
The Rock CycleIn General
Mountains are built
Weathered and Eroded
Deposited in still water
Built again
5
Rock Cycle

• 1. Types of Rock
• 2. Processes involved
• 3. Related Environmental Concepts

http//www.minsocam.org/MSA/K12/rkcycle/rkcycleind
ex.html
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Rock CycleTypes of Rock

• Types of Rock
• IgneousFire Rock
• SedimentaryRock from sediments
• Metamorphicchanged rock

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Rock CycleTypes of Rock

• IgneousFire Rock
• Rock made from magma
• From tectonics
• divergent rift zones and magma coming up
• Convergentwhere subducted plate melts
• Hot spotsmantle magma the pushes to surface
• Hawaii, Iceland, Yellowstone Park
• As magma cools it crystallizes
• If slow, some compounds crystallize first,
  crystals
• If fast, blended crystals

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Rock CycleTypes of Rock

• Igneous(Continued)
• May flow to the surface through volcanoes
• As lava, ash, projectiles
• Extrusive (basalts very common)
• May build up massive mountains

Lava flowing from a volcano in Hawaii forms
igneous rocks.
R.W. Decker, USGS
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Rock CycleTypes of Rock

• Igneous(Continued)
• May cool underground in magma chamber
• Massive blocks of crystallized rock
• Intrusive (granite very common)
• May push up under mountains, may be exposed with
  erosion

Stone Mountain, formed underground, exposed and
weathering today
http//www.windows.ucar.edu/tour/link/earth/geolo
gy/ig_intrusive.html
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Rock CycleTypes of Rock

• Sedimentary Rock
• Made from Sediment (Particles in water)
• Settles out from water in oceans and lakes
• Builds up layers
• Oldest on the bottom, newer layers on top
• Over time the weight of the overlying rock
  creates pressure
• Consolidates the sediment
• Lithification (making rock) occurs

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Rock CycleTypes of Rock

• Sedimentary Rock(Continued)
• Types deposited water
• Sediments from weathered rocks (Sand, silt, clay)
• Sediments from dead organisms
• Coalorganisms in swamp environments
• LimestoneOrganisms shells in oceans
• Precipitated Chemicals (Salt, gypsum)

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Rock CycleTypes of Rock

• Sedimentary Rock(Continued)
• From Wind deposition
• Particles carried in the wind may be deposited on
  land, build up dunes
• if buried, may lithify

Checkerboard Mesa in Zion National Park, Utah is
the remains of an ancient sand dune.
(http//www.beyondbooks.com/ear82/7.asp)
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Rock CycleTypes of Rock

• Sedimentary Rock(Continued)
• Proportions to other rock types
• Nearly 75 of continental surface is sedimentary
• Only 2 of total rock in crust, however, is
  sedimentary
• Fossil record is in sedimentary rock, no other
• Sedimentary rocks contain important information
  about the history of Earth.
• They contain fossils, the preserved remains of
  ancient plants and animals.

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Rock CycleTypes of Rock

• Metamorphic Rock
• Formed in tectonic Forge
• Heat and Pressure
• Squeezed and moved as plates collide

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Rock CycleTypes of Rock

• Metamorphic Rock
• Rock is changed
• Original rock can be igneous or sedimentary
• Examples
• Limestone turns to Marble
• Sandstone turns to Quartzite
• Shale turns to Slate
• Granite turns to Gneiss

Metamorphic Rockold sedimentary layers now folded
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Rock CycleTypes of Rock

• Metamorphic Rock
• The process of metamorphism
• does not melt the rocks,
• transforms rocks into denser, more compact rocks.
  
• New minerals are created either . . .
• by rearrangement of mineral components
• by reactions with fluids that enter the rocks.

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Rock Cycle

• Types of Rock
• Processes involved
• Mountain Building
• Weathering and Erosion
• Transport and Deposition
• Lithification
• Metamorphism
• Related Environmental Concepts

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Rock Cycle--Processes

• Mountain Building
• Without building up land in mountains
• The land would all be flat,
• no nutrients would be in the water
• One way to build mountains--Volcanoes
• Stratovolcanoes dominate some areas
• Traps (Stair-steps of basalt flows build huge
  plateaus)

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Rock Cycle--Processes

• Mountain Building
• The other way Tectonics
• Collision of plates force up mountains
• Continent to continentone overrides the other
  until the plates jam and stop
• Faulting, foldinggeneral thickening of the
  continental rock makes high mountain ranges

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Rock Cycle--Processes

• Mountain Building
• Sediments on subducting plate
• are caught between continents and bulldozed up
• (Mt Everest is topped with Limestone laid down in
  deep water in front of Indian plate)

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Rock Cycle--Processes

• Weathering
• From the moment a mountain is formed it begins to
  weather and erode
• Weatheringmaking smaller
• Mechanicalbreaking
• Ice wedging
• Wearing by water or sediments in water
• Abrading by particles carried in wind
• Chemicaldissolving
• No movement is involved in weathering

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Rock Cycle--Processes

• Erosion and Transport
• Erodingmoving away from original place
• Water, Wind, Gravity
• Relation to weathering
• Erosion of surface material allows for more
  weathering of buried rock
• Weathered rock is easier to erode
• Transportation
• Carried by water or wind to a place of
• deposition
• Water Cycletied to this part of the Rock cycle
• Dominant wind patterns may carry sand or
• dust to water bodies for deposition as
• sediments

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Rock Cycle--Processes

• Deposition
• Sediment load depends on water speed
• Sediments carried in water (or in wind) will drop
  out of suspension when the water (or wind) slows
  down
• Otherwise carried along until it gets to a
  slow-moving water body ocean or lake where it
  settles out
• Sediments settle out depending on their
  size/weight
• Heavy sediments (rock, sand) settles firstsand
  remains along coastlines, sand builds up into
  sandstone
• Lighter sediments (silt, sand) goes to deeper
  water, builds up as shale
• Dissolved ions go deeper or remain dissolved

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Rock Cycle--Processes

• Lithification
• Sediments bury other sediments
• As sediment layers are buried by other sediment
  layers the lower layers are pressed
• Downward pressure forces lower layers to
  consolidate
• They begin to lithifybecome rocks
• May be aided by chemicals dissolved in water in
  pore spacecements the rocks

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Rock Cycle--Processes

• Pressing, Folding, Heating
• Tectonic forces press laterally on rocks
• Pressure creates heat, burial insulates nearer to
  heat sources
• Pressure squeezes the rockif nowhere to go it
  may . . .
• break (fault) and move past
• Fold and bend
• As rock is heated or super-pressed
• Crystal structure changes
• Layers are compacted
• Sediment layers may be pushed sideways, upside
  down

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Rock Cycle

• Types of Rock
• Processes involved
• Related Environmental Concepts
• Mining
• Erosion

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Rock CycleEnvironmental Concepts

• Mining
• Mining products are from many different types of
  rocks
• Building Blocks (Dimension stone)
• Sedimentary rocklimestone, sandstone
• Igneous--Granite
• Fossil Fuel--Coal (sedimentary)
• Gravel--Metamorphic and granite
• Metal ores (copper, zinc, lead, gold, silver)
• Found in igneous intrusions
• Melted in magmaliquids forced into cracks and
  pockets
• Cook in ore veins
• Iron ores
• Sedimentarysediments from times of oxygen
  buildup in atmosphere (3 to 2.5 billion years
  ago)iron oxides sediments

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Rock CycleEnvironmental Concepts

• Mining (Continued)
• Impacts
• Metal ores are often bound to sulfur
• Smelting (heating) produces sulfur dioxide gas
• with water in the atmosphere makes acid rain
  (sulfuric acid)
• Mine waste rock often acidic, contains toxin
  metals
• Coal
• Open pit or strip mines, destroys landscapes
• Exposes sulfur bearing rocksrain falling on it
  makes sulfuric acid and acid mine drainage

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Rock CycleEnvironmental Concepts

• Erosion
• Soil and wind erosion
• remove large amounts of soil every year
• In depression era, western soils blown to
  Washington DC
• Exposed soils more likely to erode
• Deforestation
• Construction, urban development
• Agriculture plowed fields, overused pastures
• Mining sites

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Coal Mining
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Rock CycleEnvironmental Concepts

• Erosion
• Soil for agriculture is slow to be made
• Loss means less for crops and pasture
• Chemicals needed, fields abandoned and new fields
  made (cutting forests, plowing prairies)
• Too much soil is a pollutant in water bodies
• Swimming animals struggle to breath and feed
• Heavy deposition fills water bodies, covers
  gravel beds, clogs creeks, covers sea-grass beds
• Dirty water requires expensive cleaning for human
  consumption