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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 - PowerPoint PPT Presentation
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‘SIDE VIEW’
‘TOP VIEW’Solar System on outsideof Orion Arm (25,000 light years from centre)
100,000 ly
Nebula (dust cloud) hypothesis
Basis: observations of other systems
1. Collision or dying star in Milky Way? exploded2. Nebula (cloud of dust and gas) results3. H and He condense into Sun4. Disk of matter (many elements) around sun5. Disk slowly accretes into clumps
(planetesimals)6. planetesimals planetoids planets
(including Earth) and satellites
Eons, Eras, Periods and EpochsSuperposition: youngest rocks superimposed on older rocks “Relative time”
Dating by radioactive isotopesHalf-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)
Mountain massesdisplace mantle material
Isostatic adjustmentdue to loss of massby erosion
Deformation fromsediment load
ISOSTASYElevation of tectonic plates determined by density/thickness
MineralA natural, inorganic compound with a specific chemical formula and a crystalline structure
Examplessilicates (quartz, feldspar, clay minerals), oxides (eg., hematite) carbonates (eg., calcite)
An assemblage of minerals bound together
• Igneous (solidify & crystallize from molten magma)
• Sedimentary (settling & cementation)
• Metamorphic (altered under pressure)
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
Conglomerate largest clastsSandstone sand cemented
togetherSiltstone derived from siltShale mud/clay compacted into
rock
Limestone calcium carbonate, bones and shells cemented or precipitated in ocean
watersCoal ancient plant remains
compacted into 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
•Continents are adrift due to convection currents in the asthenosphere
•Mantle movements result in platemigration
•225 M BP: Pangaea
Age of mid-oceanic ridge magnetic stripes
Subduction zones
“Ring of fire”
Age and thickness of oceanic crust
Fossil Record (plant and animal)
Distribution of marsupials vs. placentals
Divergent Boundaries (constructional)
Convergent Boundaries (destructional)
Transform Fault Boundaries