Rocks and Minerals

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Rocks and Minerals

• Mixtures and Compounds

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Rocks and Minerals

• Rocks are mixtures of grains of minerals cemented
  together
• Minerals have well-defined chemical formulas and
  crystal structures

Amethyst, a mineral
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Some Common Minerals

• Olivine (Fe, Mg)2SiO4
• Quartz SiO2
• Feldspar NaAlSi3O8
• Mica KAl2 (AlSi3O10)(OH) 2
• Pyroxene (Mg,Fe)2Si2O6
• Amphibole Ca2(Mg,Fe)5Si8O22(OH) 2
• Calcite CaCO3
• Dolomite CaMg(CO3)2

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Lattice Structure of Quartz
Red is oxygen, blue is silicon
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Finding Composition

• Multiply the atomic mass by the subscript for
  each element in the formula
• Add them all up to get the total molar mass

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The Rock Cycle
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Igneous Rocks

• Intrusive
• Formed underground as magma cools
• Cools slowly so big crystals
• granite
• Extrusive
• Formed on surface as lava cools
• Cools quickly so small or no crystals
• obsidian

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Sedimentary Rocks

• Formed when rock particles (sediment) are fused
  together (cementation) by pressure
• Layered structure
• Named according to size or type of particles
• Sandstone, mudstone, limestone

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Metamorphic Rock

• Rocks that have undergone chemical change by high
  temperature or pressure
• NO MELTING!
• Examples
• limestone becomes marble
• shale becomes slate

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Rock Characteristics

• Porosity
• Granularity
• Hardness
• Density
• Color

• Characteristics reflect
• Mineral composition
• Method of formation

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Principle of Superposition

• Assumes no change in position of layer
• Oldest rocks will be on the bottom
• Youngest rocks on top
• Gives relative ages of the rocks

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Principle of Superposition
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Radioactive Dating

• Measure ratio of radioactive isotope to decay
  product
• Use known half life to determine age
• Gives absolute age of the rock

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WeatheringBreaking Down Rocks

• Physical
• Ice
• Plants
• Chemical
• Carbonic acid
• Acid rain
• Oxidation

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Weathering

• Some rocks are more resistant to weathering than
  others

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Physical Weathering
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Acid Rain The Same Statue
1908 1969
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Erosion and DepositionShaping the Land

• Water
• Fast moving carries lots of sediment, carves
  canyons
• Slow moving deposits sediment forming deltas
• Wind
• Arches
• Dunes
• Glaciers
• Deep U-shaped valleys
• Terminal moraines

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Grand Canyon
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Nile Delta
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Braided Rivers

• Braided rivers in Alaska carry sediment from snow
  melts to flat planes

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Rainbow Arch, Arizona
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Sand Dunes, Algeria
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Glacier Valley, Switzerland
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Terminal Moraine