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‘SIDE VIEW’ Nebular hypothesis Important theorists: Emanuel Swedenborg (1734), Immanuel Kant (1755), Pierre-Simon Laplace (1796), Victor Safronov (1972) – Solar nebular disk model (SNDM) 100,000 ly ‘TOP VIEW’ Solar System on outside of Orion Arm (25,000 light years from centre) Eons, Eras, Periods and Epochs Superposition: youngest rocks superimposed on older rocks “Relative time” Dating by radioactive isotopes Evidence: observations systems at varying stages 1. Nebula: Giant Molecular Cloud (GMC) results from collision(s) or explosion of dying star 3. H and He condense into Sun 4. Disk of matter (many elements) around sun 5. Disk slowly accretes into clumps (planetesimals) that also contain heavier elements 6. planetesimals → planetoids → planets and satellites Hubble Space Telescope view of a new solar system 1500 l-y away in the Orion Nebula Red ovals indicate major extinction events: when extinction rate greatly exceeds speciation rate Half-life: time for ½ of unstable isotopes to decay “Absolute time” Uniformitarianism: “The same physical processes active in the environment today have been operating throughout geologic time” Hutton (1795), Lyell (1830) Source: University of Calgary 1 The Earth in cross-section ISOSTASY Elevation of tectonic plates determined by density/thickness Mountain masses displace mantle material Isostatic adjustment due to loss of mass by erosion Upper mantle and lithosphere Deformation from sediment load Mineral A natural, inorganic compound with a specific chemical formula and a crystalline structure Examples silicates (quartz, feldspar, clay minerals), oxides (eg., hematite) carbonates (eg., calcite) 2 An assemblage of minerals bound together • Igneous (solidify & crystallize from molten magma/lava) • Sedimentary (settling & cementation) • Metamorphic (altered under pressure) Laccolith • from magma ( lt rockk (molten beneath the surface) • intrusive or extrusive (from lava) Sill plutons Dike Batholith 3 Existing rock or organic material is digested by weathering, picked up by erosion, moved by transportation, and deposited at river, river beach and ocean sites. Lithification follows (cementation, compaction and hardening) Conglomerate Sandstone Siltstone Shale Limestone Coal Laid down in horizontally-layered beds largest clasts sand cemented together derived from silt mud/clay compacted into rock calcium carbonate, bones and shells cemented or precipitated in ocean waters ancient plant remains compacted into rock Any type of rock is transformed, under pressure and increased temperature Harder and resistant to weathering note the shells Produced from any rock type by: •Compressional forces due to plate collisions •Regional and contact metamorphism Crustal Movements Shale Slate Granite Gneiss Basalt Schist Limestone, dolomite Marble Sandstone Quartzite 4 •Continents are adrift due to convection currents in the asthenosphere •Mantle movements result in plate migration •225 M BP: Pangaea Continents Adrift Fossil Record (plant and animal) Distribution of marsupials vs. placentals Age of mid oceanic ridge magnetic stripes mid-oceanic Age and thickness of oceanic crust Subduction zones “Ring of fire” 5 Mid-oceanic ridge magnetic stripes See: http://www.scotese.com/sfsanim.htm (animation) Divergent Boundaries (constructional) Convergent Boundaries (destructional) Transform Fault Boundaries URL: http://pubs.usgs.gov/publications/text/Vigil.html 6 Source: USGS Earthquakes and Volcanoes 7