ROCKS AND MINERALS

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ROCKS AND MINERALS

• GEOLOGY

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Rocks and Minerals

• Rock - solid matter made from minerals or
  petrified organic materials.
• Mineral - naturally occurring homogeneous
  inorganic solid having a definite chemical
  composition and a unique crystal structure, color
  and hardness

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• Igneous rocks - hot liquid cools and becomes
  rock. There are three types
• Intrusive Igneous -- formed inside the earth from
  magma chambers
• Magma - Hot liquid found under the earths surface

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• Intrusive Textures
• Porphyritic texture - large crystals imbedded in
  a smaller matrix
• Phenocryst - Conspicuously large crystal imbedded
  in a matrix of finer crystals

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• Phaneritic texture- igneous rock texture -
  crystals are roughly the same size - large enough
  to be seen with the unaided eyeEXAMPLES
• Granite - phaneritic 25 quartz and 50 feldspar
• Diorite - coarse grained intrusive - no visible
  quartz crystals
• Gabbro - dark green/ black - pyroxene and
  plagioclase

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• Extrusive Igneous -- formed on the surface of the
  earth in a lava flow or lava shot from a volcano
• Lava - molten rock that reaches the earths
  surface through a volcano or fissure
• Extrusive Textures
• Aphanatic - igneous rock texture in which the
  crystals are too small to be seen with the
  unaided eye

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• EXAMPLES of Aphanatic Textures
• Rhyolite - volcanic equivalent of granite
• Obsidian - dark colored glassy rock
• Pumice - volcanic rock with a glassy texture
• Andesite - medium grey fine grained rock
• Basalt - dark green/ black - pyroxene and
  feldspar extrusive equivalent of gabbro

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• Crystallization - process where ions arrange
  themselves into orderly patterns as magma cools

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• Pyroclastic rocks- shot from a volcano (still
  igneous)
• Tuff - frothy volcanic ash formed from huge
  sudden volcanic events
• Volcanic breccia - volcanic rocks composed of
  particles larger than ash
• Bombs - large solid rocks ejected by volcanoes

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• Sedimentary rocks - from when sediments from
  erosion are cemented together. There are two
  types
• Clastic- made from broken pieces of other rocks
• Made from Mud, silt, sand, gravel
• Examples
• Shale- Mud and silt
• Sandstone- Sand
• Conglomerate- gravel

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• Chemical Sedimentary rocks - form from minerals
  dissolved in H2O
• When temperature of water lowers ions come out of
  solution.
• Have smooth textures -intergrown crystals
• EXAMPLES-
• Rock salt - Halite
• Limestone (not all)
• Rock Gypsum

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Metamorphic Rocks

• Metamorphic rocks are rocks that have "morphed"
  into another kind of rock. These rocks were once
  igneous or sedimentary rocks.
• The rocks are under tons and tons of pressure,
  which fosters heat build up, and this causes them
  to change underground.
• As a result, most of the thousands of rare
  minerals known to science occur in metamorphic
  rocks.
• The presence of mineral layers, called foliation,
  is important to observe when identifying a
  metamorphic rock.

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How do they form?

• Metamorphic rocks form deep in the earth where
  high temperature, great pressure, and chemical
  reactions cause one type of rock to change into
  another type of rock.
• This happens 12-16 kilometers beneath the earth's
  surface and at temperatures of 100 degrees
  Celsius to 800 degrees Celsius.
• If you squeeze and heat a rock for a few million
  years, it can turn into a new kind of rock

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Characteristics of Metamorphic Rocks

• Classified by texture and composition
• May have alternate bands of light and dark
  minerals
• May be composed of only one mineral, ex. marble
  quartzite
• May have layers of visible crystals
• Usually made of mineral crystals of different
  sizes
• Rarely has pores or openings
• May have bent or curved foliation

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Examples

• Some examples of how metamorphic rocks were
  changed

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The Rock Cycle with Environments
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The Rock Cycle
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Earths Layers

• Inner Core Nickel and Iron
• Solid -- diameter is 1480 km
• Outer Core Nickel and Iron
• Liquid -- 1990 km thick

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Earths Layers

• Lower Mantle
• Solid -- 2165 km thick
• Upper mantle (Athenosphere)
• Plasticlike part is 600 km
• Rigid top part is 75 km

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Earths Layers

• Crust
• Continental -- Si rich
• Oceanic -- Fe and Mg rich

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Bowens Reaction Series

• When two tectonic plates collide one may be
  pushed down into the mantle. It heats and melts
• Magma that is made will have different chemical
  composition depending on where it comes from.

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Bowens Reaction Series

• Magmas from Continental Crust - rich in silicon
  and aluminum
• Magmas from oceanic crust - rich in iron and
  magnesium
• Composition determines which rocks will be made
  when magma cools

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Bowens Reaction Series

• N.L. Bowen - showed that cooling magmas produce
  minerals in a predictable order
• Two sides - Iron (Fe) rich side and a calcium /
  sodium (Ca / Na) rich side.

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Bowens Reaction Series

• Olivine - First Fe rich mineral to form - in
  tetrahedra shape - easily weathered on the
  surface
• Pyroxenes - Tetrahedra link in long chains -
  also weather easily

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Bowens Reaction Series

• Amphiboles - double strands made from linking
  pyroxenes
• Micas - amphibole chains make sheets
• Feldspar - from the Ca/Na side like olivine but
  Al is inside the tetrahedra vs. Si

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Bowens Reaction Series

• Feldspars - as temp cools Ca and Na replace Al
  inside the tetrahedron
• Quartz - very low temperatures - little left in
  magma except Si and O -three dimensional networks