ESS105 Summary part 1 of course

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University of Toronto St. George
Earth Sciences
Lisa Tutty

LECTURE 1 electrons holding them together, but individual atoms not held to any other specific Geology – study of solid earth and processes by which shaped and changed Hypothesis: atoms so slip past each other easily – ductile Hazards - Earth is divided into mechanical layers MICAS/graphite – van der waals (intermolecular forces) Diamond – stable at high pressure, low temp - Volcano – lava, hot volcanic ash, gas, mudflows, nutrients - Outer layer is rigid lithosphere floating on plastic asthenosphere Diamond and graphite are polymorphs - Landslide – too steep What is Plate Tectonics? TENACITY – how does a mineral resist breaking/deforming Lithosphere divided into plates – some have continents - Elastic – bends and returns (e.g. mica) - River – flood, water, transport, energy, fertile floodplains NorthAmerican Plate, Mid-Atlantic Ridge, Eurasian Plate – diverging THEORY OF PLATE TECTONICS - ~1960s - Flexible – bends and stays (e.g. talc) - Soil – some dangerous to build on (liquefaction/shrink/swell) - Earth’s lithosphere divided into plates that move relative to one another, and relative to underlying asthenosphere - Malleable – can be hammered (e.g. copper) - Earthquakes – Slip along faults Natural resources - As plate move, their interiors remain relatively intact, while their boundaries undergoe – easily broken (e.g. halite) deformation FRACTURE – irregular (e.g. quartz Concoidal) - Natural resources – distribution of iron vs. copper mines CLEAVAGE – along smooth planes (calcite – perfect) EVIDENCE FOR PLATE TECTONICS Crystal Faces – stacking of building blocks (called unit cells) each contain multiples Canada’sphysiographicregions –rockies, arctic,plains, great lakes, maritimes of chemical formula, very symmetrical overall body – e.g. cubic crystals galena, - Great lakes – a few found within “Canadian Shield” landscape - Continents were connected: diamond, garnet - Matching coastlines, similar rocks, glacial features “cross” oceans, same fossilssical property – density – depends on: atomic mass, size ions, packing - Gneiss – records intense deformation at great depths when crustal blocks collided to make up Lustre – how much light is reflected – metallic, adamantine, vitreous (quartz), the crustal mosaic that comprises oldest part of Canada (e.g. Glossopteris, Mesosaurus – SouthAmerica andAfrica) pearly (mica) - Alfred Wegner’s (proposed continental drift hypothesis) Evidence: Transparency – is light being transmitted? Transparent – e.g. calcite, translucent – - Rockies – Castle Mountain (main range mountain caused by collision of tectonic plates) – high e.g. agate, opaque – amazonite (feldspar) elevation – glaciers – Wapta icefield Electric properties: can electrons move? Metallic – conductors, covalent – - Sinkhole – caused by karst – karstification – soft carbonate bedrock - Glacier scratch marks near equator insulators Colour Hazardous geologic processes BC - Earthquakes: Mediterranean-Himalayan seismic belt, circum-pacific seismic belt- Chromophore elements – e.g. Cu in malachite/azurite (blue) - Volcanoes - Volcanoes – ring of fire - “wrong” atom in structure – e.g. purple fluorite or amethyst – Fe) - JuandeFucaplatesubductingunderNorthA.plate(Cascadiasubductionzone) - Mountain belts: alps and Himalayas - Diffraction of light at small structures – e.g. opal - Queen Charlotte Fault – active transform fault - More evidence: age of ocean floor – ocean floor is young, as are ocean Streak – colour of powdered mineral – useful to distinguish ore minerals (e.g. sediments (all <190 MYO) hematite has a red streak) - Lots of high-magnitude earthquakes 3 TYPES PLATE BOUNDARIES Economic minerals – ones people go out to mine to make money – most have Sulphide mine – contaminated groundwatermine drainage” streaks Energy and Forces - Divergent, Convergent, Transform What’s special about gemstones? Typically cut to enhance optical properties – Sun – external energy, earth – internal energy different cuts – different number of faces in terms of orientation How do Forces and Pressures Affect Earth? Convergent – subduction, often ocean trench, volcanic arcs, mountains (e.g. W. Otherproperties:magnetism(magnetite),thermal(metalsconductheat),fluorescence, SouthAmerica) reactionwithacid,radioactivity(e.g.uraninite),plezoelectricity(e.g.quartz)–generatean - Uneven solar heating FEATURES DEPEND ON KIND OF LITHOSPHERE: ocean-ocean (e.g. Japan), electricfieldorelectricpotentialinresponsetoappliedmechanicalstress ocean-continent (e.g. S.America), continent-continent (e.g. Himalayas) Diamond value – carat clarity, colour, cut - Radioactive decay Divergent plate boundary – MOR (e.g. Iceland – MOR exposed) 1 carat = 0.2g Continental Rift (e.g.African Rift Valley (below)) Diamond slightly heavier than quartz for same diameter - Air pressure Brilliant cut has 57 facets at specified angles to maximize sparkle - Rocks squeezed Transform boundary – 2 plates sliding past one another 1. Diamondsfoundinkimberlites –volcanic rocks that cameupfrom Sediments: Connect convergent and divergent boundaries (e.g. SanAndreas fault) ~150kmdepth, small areas,easily fencedoff–expensivetomine–minedby large - Glaciers erode, transport, and deposit sediment companies (reverse fault) 2. Diamonds also eroded and transported in rivers – alluvial - Cliffs lose sediment by erosion Active transform fault connects crests of MOR while inactive fossil transform faultsdiamonds, in large diamond fields – mostly mined by individuals (e.g. - Rivers erode, transport, and deposit (= fracture zones) stretch away from MOR garimpeiros in Brazil), often below poverty line Inactive fault means same direction Warlords – must fulfill quota for day - Sand dunes – wind erosion neobeum –biggestsalesfrom democraticrepublicof congo, somecompaniesnes, - Beaches collect sediments Oldest continental rock is ~4 billion years old, oldest ocean rock ~180 Ma moreresponsible–required reportingof suppliesinUSsince2010 Why do tectonic plates “float” on the mantle? – light continental crust stands ouIn Canada – 2 mines operating, 3 more mines soon Sedimentary Rocks water, dense oceanic crust covered by water High quality, high ore grade, but small “pipes” - Clastic ISOSTASY – a floating body replaces as much volume as corresponds its weight 10-100m across FORCE BALANCE – weight is balanced by buoyancy Magnometer measures magnetic character of rock – kimberlites very magnetic, - Chemical - Blocks of same weight but different densities have same volume below water even if covered by trees Who has right to land vs. right to minerals o Biogenic or evaporate (Death Valley) - Blocks of same density but different height have same properties above and Environmental regulation – miners must prove won’t destroy environment – usually Sedimentary hydrothermal rocks (deposited by hot water) below water cut down forests, drainage toxic, floods Mesa, Butte, Hills & Knobs PROBLEM: Value of diamonds depends on clarity – but clear diamonds are
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