Lecture1 - What are Earth Systems? 7.2 magnitude, January...

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Unformatted text preview: What are Earth Systems? 7.2 magnitude, January 03, 2010 22:36:28 UTC, Solomon Islands What are Earth Systems? 7.1 magnitude, January 02, 2011 05:20:18 UTC, Araucania, Chile 1 What are Earth Systems? 9.0 magnitude, March 11, 2011 05:46:24 UTC, Honshu, Japan What are Earth Systems? Yellowstone Ottawa 2 Yellowstone Yellowstone 3 Ottawa On June 23, 2010 at 1:41:42 EST a 5.0 magnitude earthquake 32 km north of Buckingham, Quebec What are Earth Systems? Yellowstone Ottawa New Madrid zone 4 Earth Systems? Trauma cited in mysterious Ark. bird kill USAToday (Jan 2011) ~2000 birds fall from sky (unrelated?) ~80,000 to 100,000 freshwater fish wash onshore The science of Geology Geology is the science that pursues an understanding of planet Earth Modern approach is to examine Earth as a SYSTEM: Atmosphere Biosphere Hydrosphere Cryosphere Lithosphere 5 The science of Geology Geology is the science that pursues an understanding of planet Earth • Physical geology - examines the materials composing Earth & seeks to understand the many processes that operate beneath & upon its surface • Historical geology - seeks an understanding of the origin of Earth & its development through time Physical Geology will it last? why does it degrade? what is it made of? what is steel? what is concrete? is it unique? how is it different? how is it put together? what are the mechanics behind its functionality? 6 Physical Geology 1st half Mineralogy • Composition & structure of steel & concrete Rock Cycle • Making of steel or concrete Geodynamics (e.g. mountain building) • Bridge construction Earth Surface Processes 2nd half • Gradual or rapid destruction of bridge Earth Systems • Interaction between bridge, people, autos, weather… The science of Geology Geology is the science that pursues an understanding of planet Earth science: the intellect & practical activity encompassing the systematic study of the structure & behaviour of the physical & natural world through observation & experiment 7 The nature of scientific inquiry Science assumes the natural world is consistent & predictable Geology differs from other sciences: 1) Deals with large spatial-scales & complex systems • controlled experiments are difficult / impossible • observation & description acquire proportionately more importance Nanga Parbat, Pakistan - 8.1 km (8100000000 microns) Zircon crystal (200 microns) The nature of scientific inquiry Science assumes the natural world is consistent & predictable Geology differs from other sciences: 2) Deals with time scales that are immense compared to human lives • impossible to observe entire process directly (only able to view snapshots) • spatial variation can be interpreted as temporal evolution • Principle of Uniformitarianism: geological processes & natural laws that operate today have acted throughout geologic time 8 oldest continental rock: 4.5 billion years old extinction of dinosaurs: 65 million years ago evolution of Homo sapiens: 0.5 million years ago last glacial maximum: 15,000 years ago duration of average earthquake: <10 seconds The nature of scientific inquiry Science assumes the natural world is consistent & predictable Geology differs from other sciences: 3) Geologic evidence is fragmented / incomplete • conclusions & models may be non-unique and dependent on intuition & experience 9 knowledge + experience = wisdom emphasis on the collection & interpretation of field data • discern signal:noise the natural laboratory art & science of "geologizing" - geocognition organize & resolve disparate data sources • Geo2020 Field studies I (Appalachians) • Geo3920 Field studies II (Abitibi) • courses with field excursions • student thesis research 10 The nature of scientific inquiry Science assumes the natural world is consistent & predictable Scientists collect "facts" through observation & measurements, but facts are secondary to understanding Goal of science is to discover patterns in nature & use the knowledge to make predictions It's not what you know, but how you know it! The nature of scientific inquiry How or why things happen are explained using: 11 The nature of scientific inquiry How or why things happen are explained using: Inductive (Baconian) method early stages;• collection of data without regard to theory recon • expect explanation will become apparent from organization & synthesis of large data sets Deductive (Darwinian) method later stages; focused • devised model(s) accounts for set of observations, and used to make predictions about nature • iterative The nature of scientific inquiry How or why things happen are explained using: • Hypothesis (model) – a tentative (or untested) explanation --- model: testable, powerful, parsimonious • Theory – a well-tested & widely accepted view that the scientific community agrees best explains certain observable facts • Law – high degree of confidence 12 The nature of scientific inquiry Deductive scientific method 1) Collection of scientific facts (data) 2) Development of one or more working hypotheses to explain the facts 3) Development of observations & experiments to test the hypotheses 4) Acceptance, modification, or rejection Dinosaur example! 13 A scientific inquiry Step One: Data collection or observations • Dinosaurs extinct @ ~65 Ma • Many plankton extinct @ ~65 Ma • Many(!) other organisms extinct @ ~65 Ma • Extinction was FAST • Corresponds to unique geochemical anomalies (Ir, S, C) in rock record Ma = mega-annum = millions of years = 106 years Ga = giga-annum = billions of years = 109 years 14 65 Ma Iridium (platinum group metal) found in: • Earth's primordial lavas & the core • meteorites, comets, cosmic dust Sulfur derived from: Bolide impact on evaporite/carbonate terrain (Volatilization of gypsum/anhydrite : SO42-) Volcanism releases S (Reduced gases, SO2 … oxidized to SO42-) 65 Ma K‐T 15 Carbon… (terrestrial C) 65 Ma A scientific inquiry Step Two: Theory development • Comet or asteroid impact created the geochemical anomalies (vs. lava eruptions) • Testable? Side effects? • Crater(s) • Dust cloud + fireball = "nuclear winter" instant death (vs. synchronous numerous and thick lava flows) 16 A scientific inquiry Step Three: Observations & experiments • Test/confirm world-wide geochemical anomalies • Test/confirm abrupt end to dinosaurs & plankton • Identify crater } multiple working hypothesis • Identify large lava eruptions Step Three: volcanic origin? Deccan Traps (India) flood basalts; 60-68 Ma > 2,000 m thick area > 500,000 km2 volume > 512,000 km3 17 Step Three: bolide impact? Wanapitei crater, ON, 37 Ma Manicouagan crater, QC, 214 Ma Charlevoix crater, QC, 342 Ma Sudbury crater, ON, 1850 Ma Sudbury crater, ON, 1850 Ma nickel, copper, platinum, palladium, gold 18 Chicxulub crater: 65 Ma 19 Step Three: bolide impact? • Crater identified • Anomalies associated with ash, soot, glass (tektites) A scientific inquiry Step Four: Accept, modify, reject? • Almost abrupt end to terrestrial & marine life • Geochemical anomalies are world-wide • Anomalies associated dust cloud/fireball • Crater! • No large lava eruptions Law??? 20 Theory of Plate Tectonics Plate Tectonics • composite of ideas that explain the observed motion of Earthʼs lithosphere thru mechanisms of subduction & sea-floor spreading which generate continents & ocean basins The solar system and the origin of Earth Read chapters 12 & 24 for Monday 21 ...
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This note was uploaded on 03/26/2012 for the course GEO 1111 taught by Professor Dumas during the Winter '09 term at University of Ottawa.

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