Download Rocks - c2cmsp

Earth’s Interior and the Rock
Cycle
Earth’s Interior
• Four Layers
• Each has a
different
composition
and density
(mass/volume).
CRUST - Outermost layer
• Density = low
• Composition is silicon and oxygenbased minerals and rocks.
• Crust is extremely thin.
• Consistency is rocky.
Composed of two general types.
Continental crust
Oceanic crust
Crust consists of Oceanic Crust
(brown) Continental Crust (green).
• Oceanic crust is
thin (8-10 km),
dense, and found
below ocean basins.
• Continental crust is thicker
(20-70 km), has low density and forms the
bulk of continents.
MANTLE - Middle thin layer
• Density = medium
• Composition is silicon
and oxygen-based.
• Also includes iron
and magnesium.
• Consistency is plastic.
• Two main regions, Upper and
Lower Mantle.
Lithosphere (rock layer) - Contains parts of
the upper mantle and all of the crust.
• Strong layer, but brittle.
• Represents outer ~100 km of the Earth.
• Thicker where continents exist, thinner
under oceans.
Below the lithosphere resides the
Asthenosphere (weak layer).
•Heat softened and acts like a plastic.
•It is weak, slow flowing, yet solid rock.
•Found 100-350 km beneath Earth’s surface.
CORE – Center layers
• Density = high
• Composition is primarily iron
and nickel.
•Contains two parts
Outer core is liquid.
Inner core is solid.
Rock Types and the Rock Cycle
Rock - a naturally occurring aggregate of
minerals formed within the Earth.
Basaltic Dike
Acadia Nat’l Park,
Maine
Delicate Arch, Arches Nat’l Park, UT
Rock Types and the Rock Cycle
A Mineral is/has:
1. Naturally occurring
2. An inorganic solid
3. Made of a single element or compound
4. Definite chemical composition
5. Orderly arrangement of atoms.
Pyrite
FeS2
Diamond
C
Beryl
Be3Al2(Si6O18)
Rock Types and the Rock Cycle
•Three types of rocks.
•These are present in the crust and at the
Earth’s surface.
•Each have fundamentally different
origin.
1. Igneous
2. Sedimentary
3. Metamorphic
Igneous Rocks
• Cooled and solidified from Molten material.
• Formed at or beneath the Earth’s surface.
• Melting of pre-existing rocks required.
Granite
Basaltic
Lava
Igneous Rocks – 2 major subdivision
Intrusive Igneous
•Formed under ground
•Usually medium to coarse grained texture
due to slow cooling.
•Typically light colored.
Extrusive Igneous
•Formed on surface
•Glassy or fine-grained due to rapid cooling
•May have voids due to degassing of magma
•Typically dark colored.
Extrusive (volcanic)
Intrusive (plutonic)
Sedimentary Rocks
• Pre-existing rocks are weathered and
broken into fragments that accumulate.
• Are then compacted or cemented together.
• Also forms from precipitates or organisms.
Sedimentary Rocks
• Formed by the lithification of
unconsolidated sediments - compaction and
cementation
• The weight of overlying sediments causes
sediments to be reduced in volume by 40%.
•Increases pressure and temperature
causes some minerals to melt - filling
spaces between remaining grains.
•They then harden to form a glue or
cement: cementation
Metamorphic Rocks
• Form when pre-existing Earth materials are
subjected to heat, pressure and/or chemical
reactions and change the mineralogy,
chemical composition and/or structure of the
material.
Gneiss
Coal
Slate
Metamorphic Rocks
• Generated by recrystallization of either
igneous or sedimentary rocks by the action
of any or all of the following:
•Pressure
•Temperature
•Pore Fluids
• The lower temperature limit is 150 °C.
• The upper limit is the melting temperature
when magma forms.
• Type of metamorphic rock is determined
by the parent rock, and the P/T conditions.
Any rock type can become any other
rock type given time and processes
acting on them.
These changes are reflected in the
ROCK CYCLE.
Here is another version of the Rock Cycle
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Metrocks/Metrocks2.html
The Rock Cycle
Several key processes change rocks:
•Weathering: the physical and chemical
breakdown of rock.
•Transportation: the transportation of from
the weathering site
•Deposition: the deposition of sediments after
transportation
•Lithification: sediments turning into rock by
the processes of compaction and cementation
•Melting: The heating of solid rock till it
melts
•Metamorphism: The changing of rock by
heat, pressure &chemically active
fluids
•Crystallization: The growth of crystals
from a cooling magma
•Uplift and exposure: The movement of
rock to the surface by weathering &
erosion, faulting etc
•
http://www.earth2class.org/er/students/256,1,Rocks
•
http://www.colby.edu/~bfrueger/141/316,4,Slide 4
•
http://sun.menloschool.org/~cfat/powerpoint/earth_science/276,5,Slide 5