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EARTH

EARTH. A DYNAMIC PLANET. Geography 1000B. ‘SIDE VIEW’. 100,000 ly. ‘TOP VIEW’ Solar System on outside of Orion Arm (25,000 light years from centre). Solar system formation. Nebula (dust cloud) hypothesis Basis: observations of other systems

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EARTH

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  1. EARTH A DYNAMIC PLANET Geography 1000B

  2. ‘SIDE VIEW’ 100,000 ly ‘TOP VIEW’ Solar System on outside of Orion Arm (25,000 light years from centre)

  3. Solar system formation • Nebula (dust cloud) hypothesis • Basis: observations of other systems • Collision or dying star in Milky Way? exploded • 2. Nebula (cloud of dust and gas) results • 3. H and He condense into Sun • 4. Disk of matter (many elements) around sun • 5. Disk slowly accretes into clumps (planetesimals) • 6. planetesimalsplanetoidsplanets (including Earth) and satellites

  4. GEOLOGIC TIME SCALE Eons, Eras, Periods and Epochs Superposition: youngest rocks superimposed on older rocks “Relative time” Dating by radioactive isotopes 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)

  5. Red ovals indicate major extinction events Source: University of Calgary

  6. The Earth in cross-section

  7. Upper mantle and lithosphere

  8. ISOSTASY Elevation of tectonic plates determined by density/thickness Mountain masses displace mantle material Isostatic adjustment due to loss of mass by erosion Deformation from sediment load

  9. THE ROCK CYCLE 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)

  10. Rock An assemblage of minerals bound together • Igneous (solidify & crystallize from molten magma) • Sedimentary • (settling & cementation) • Metamorphic • (altered under pressure)

  11. Igneous Rock Formation • from magma (molten rock beneath the surface) • intrusive or extrusive (from lava)

  12. Igneous Structures Laccolith Sill plutons Dike Batholith

  13. Sill

  14. Sedimentary Rock Existing rock or organic material is digested by weathering, picked up by erosion, moved by transportation, and deposited at river, beach and ocean sites. Lithification follows (cementation, compaction and hardening) Laid down in horizontally-layered beds

  15. Defined by clastic origin Conglomerate largest clasts Sandstone sand cemented together Siltstone derived from silt Shale mud/clay compacted into rock Limestone calcium carbonate, bones and shells cemented or precipitated in ocean waters Coal ancient plant remains compacted into rock or by chemical / organic origin

  16. note the shells

  17. Metamorphic Rock Any type of rock is transformed, under pressure and increased temperature • Harder and resistant to weathering • Produced from any rock type by: • Compressional forces due to plate collisions • Regional and contact metamorphism

  18. Original rock Metamorphic rock Shale Slate Granite Gneiss Basalt Schist Limestone, dolomite Marble Sandstone Quartzite

  19. Crustal Movements

  20. Continental Plates

  21. CONTINENTAL DRIFT • Continents are adrift due to • convection currents in the • asthenosphere • Mantle movements result in plate • migration • 225 M BP: Pangaea

  22. Continents Adrift

  23. PROOF OF CONTINENTAL DRIFT Fossil Record (plant and animal) Distribution of marsupials vs. placentals Age of mid-oceanic ridge magnetic stripes Age and thickness of oceanic crust Subduction zones “Ring of fire”

  24. Mid-oceanic ridge magnetic stripes

  25. See: http://www.scotese.com/sfsanim.htm (animation)

  26. PLATE BOUNDARIES Divergent Boundaries (constructional) Convergent Boundaries (destructional) Transform Fault Boundaries

  27. URL: http://pubs.usgs.gov/publications/text/Vigil.html

  28. 'RING OF FIRE'

  29. HOT SPOTS Source: USGS

  30. Earthquakes and Volcanoes

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