GLG 110: Environmental Geology

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GLG 110 Environmental Geology
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What are we made of? People (and other living
things) are made mostly of carbon (C) and
hydrogen (H) with some nitrogen, oxygen,
phosphorus, and sulfur (organic compounds), and
a little bit of all of the other elements.
What is the Earth made of? Solid Earth Iron
32.4 Oxygen 29.9 Silicon 15.5 Magnesium
14.5 Sulfur, Nickel, Calcium, Aluminum, others
2 or less
Atmosphere Nitrogen 78 Oxygen 21 and Ar, CO2,
Ne, He, Methane and pollutants lt1
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Rocks and Minerals What is a mineral? What is
a rock?
Mineral An inorganic, naturally-occurring,
crystalline solid, with a specific chemical
composition.
Examples quartz (SiO2), calcite (CaCO3), halite
(NaCl), olivine ((Mg,Fe)2SiO4)
Rock An aggregate of minerals.
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N.B. In chemical bonding, electrons
swapped between atoms -- unlike radioactivity, no
change to the atomic nucleus!
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TYPES OF CHEMICAL BONDS Cations lose
electrons, form positive ions Anions gain
electrons, form negative ions Ionic bonds
transfer of electrons forming a cation and anion
(e.g. NaCl) most minerals have ionic
bonds. Covalent bonds sharing of electrons
between atomic nuclei very strong bonds, e.g.
diamond consisting of only covalently bonded C
bonds.
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Silicon-Oxygen Tetrahedron
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Linking up Si-tetrahedra to make Silicate Minerals
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Quartz SiO2
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Feldspar Framework Silicate
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Tourmaline Ring Silicate
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Linking up Si-tetrahedra to make Silicate Minerals
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Magnetite Fe3O4
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MINERAL OR NOT?
Coal?
NOPE! not a definite composition
Sorry, Not crystalline
Chert (amorphous SiO2)?
Fools gold (pyrite)?
YES! Crystalline FeS2
Gallium Arsenide (semi-conductor)?
No, not naturally-occurring
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Asbestos Minerals
Chrysotile (Layer Silicate) 95 of Commercial
Industrial Asbestos
Crocidolite (Amphibole Grp.) 5 of Commercial
Industrial Asbestos Linked to Lung Disease
Cancer
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Sedimentary Rocks
Shale fine-grained Sediment clay
Sandstone medium-grained Sediment sand
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Sedimentary Rocks
Conglomerate course-grained Sediment pebbles,
cobbles, boulders
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