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ESS102H1 (104)


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University of Toronto St. George
Earth Sciences

GLG103 Geology in Public Issues What will you learn in this course? - Plate tectonics - How different geologic hazards occur - Human influenced and impacts of hazards - Natural resources (water, metal, gas nuclear) - Global climate change Critical evaluation of news stories. Important Dates - Last Day to + Classes Sep 25 - Test 1: Oct 17 - Last Day to drop Nov 3 - Test 2 – Nov 21 Tests are worth 25% Exam is worth 45% Minute Reports 5% - Almost Participation Marks How are humans agents of environmental change? 1. Japan – Huge measures taken before Tsunamis and earthquakes. Less death toll, but all fail-safes…failed. 2. Thailand – No one educated, lack of safe infrastructure; big death toll. 3. New Orleans – Human engineering caused a natural disaster to become a catastrophe. 4. Famine in Somalia – Natural phenomenon of drought. Now however, issues of overpopulation, lack of ability to migrate 5. Alberta Oil Sands - Heavy levels of containments in the Athabasca river. September 14 th Lecture 2: The Earth’s Structure and Composition The Science of Geology  Geo “earth”, logos “discourse” Geology, people & the environment  Relationships between people and the natural environment include  Natural hazards, resources, world population growth & environmental issues. Some Historical notes about geology  Catastrophism: shaping of the Earth’s andscape by catastrophes.  Uniformitarianism “the present is the key to the past” – James Hutton, became principle for modern geology Both were right in some regards. Geologic Time  Exceedingly long time…the earth is 4.6 BILLION years old!  An appreciation for the magnitude of geologic time is important because many processes are very gradual  Techniques give us fairly accurate ages of the earth  However, they are constantly being refined. Formation of Earth’s Layered Structure  Chemical segregation early in the formation of Earth by gravity -Core – inner layer, dense, iron rich -Crust – solid thin outer layer -Mantle – largest layer between core and crust composed of iron & magnesium  Layers defined by composition are four main ones. - Lithosphere – rigid outer rind of Earth approx. 60-100km thick Continental Lithosphere :silica rich- lower density Oceanic lithosphere – thinner, but thicker density - Asthenosphere Densities increase as you go further into the earth. Plate Tectonics; Development of the Theory - Continental Drift : 1912 Alfred Wegener - Seafloor Spreading: 1960 Harry Hess Evidence for Pangaea & Continental Drift - Geometry of continent shorelines - Matching ancient rocks & fossils - Ancient ice-sheet glaciation Interesting When magnetic north changes position, magnetic rocks point in direction of magnetic north, changing direction. Planet of Shifting Plates - Plate Tectonics - Lithospheric Plates move relative to one another at very slow rates - Movement driven by convection in mantle Lithospheric Plate Boundaries: Convergent, Divergent, & Transform Divergent Boundaries – Spreading Zones - Oceanic Spreading Oceanic ridges (Mid Atlantic) Convergent Boundaries - Subduction Zones Ocean-Continent Collision Continent volcanic arc of strata volcanoes form from the heating of the subducting plate and the melting of the overlying mantle and continental crust. Continent-Continent Collision: not a lot of subduction ->Himalayas The Rock Cycle - Sedimentary Rock Formed from sediments (sometimes call parent material) Sediments created by -erosion of any type of rock -dissolved minerals creating precipitate -accumulation of organic debris Turned into rock(lithification) -occurs due to Compaction: when water is squeezed out of sediment Cementation: minerals act as a glue which holds the rock together The Rock Cycle Igneous Rock -Formed by solidification of molten material(magma) - Can solidify above (extrusive) or below the earth’s surface (intrustive) - INTRUSTIVE AND EXTRUSIVE ROCK NOTES FROM PPT Convection: - The transfer of heat by circular movement of liquids or gases - Convection can occur both above the earth (clouds) or below the earth (moves plates) - Hotter rocks are less dense and rise; cooler rocks re more dense and fall due to gravity. Metamorphic Rock - Any type of rock (igneous, sedimentary or metamorphic) modified by heat, pressure and chemical processes - Foliated metamorphic rocks show bands or layers - Non foliated metamorphic rocks have a smoother appearance (e.g marble) - No melting of the rock occurs - Rock is usually altered beneath the earth’s surface - Contact metamorphism occurs when rock changes when in contact with hot lava/magma The Earth as a System What Are Nutrients? - Any chemical required for the proper functioning of an organism C, H, P, S, Ca, Mg, K, O - Products of one system are food for another (Feces-> Bacteria) - Everything becomes recycled ideally. The Carbon Cycle - Large quantities are transferred from one compartment to another - Stored in 4 spheres - as molecules in organisms in biosphere - as a gas in atmosphere - as organic material, fossil fuels litho - MISSING POINT PPT Carbon is removed by photosynthesis - approximately 110 billion metric tonnes/year - returned by respiration of plants and animals (50 billion metric tonnes) and decomposition (decay 60 billion tonnes) This does not account for all C removed by photosynthesis. We are not 100 informed on Carbon Cycle The Phosphorus Cycle - found in rocks and minerals as phosphate - typically bound in insoluble chemical precipitates - unique in that it does not cycle through atmosphere - does not have a gas phase The Nitrogen Cycle - Processes: - Fixation: needs to be processed for organism to be used, usually by bacteria and sometimes lightning strikes - Assimilation: absorbed by organisms - Mineralization/Ammonification: conversion of nitrate (expelled by organisms) into ammonia by bacteria - Nitrification: conversion of ammonia back to nitrate by bacteria - Denitrification: Reduction of
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