ESS105H1 Study Guide - Final Guide: Cinder Cone, Shield Volcano, Mantle Convection

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23 Jul 2016
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Chapter 3
- How does continental drift explain glacial deposits in unusual places?
oCrops identical to glaciers in Africa
oThe scratchmarks on them tell the direction they moved from
oWegener discovered that from the scratchmarks that continents must have been pieced
together
- The LITHIOSPHERE is broken up into pieces called tectonic plates
- Tectonic activity occurs near plate boundaries
- What happens at mid ocean ridges?
oA rift runs along the axis of mid ocean ridges
oThis movement causes faulting
oSolid mantle in asthenosphere rises towards the surface
oThe magma erupts and solidifies on the seafloor
- Continental rifting: continents spreading apart (East Africa)
- Rifting can cause seafloor spreading and lead to the formation of a new ocean basin
- Ocean trenches, island arcs and earth’s largest mountain belts form at convergent boundaries
- Convergence of oceanic plates:
oOne plate slides under another (subduction)
oOceanic trench forms
oSediment collects in trench, forming accretionary prism
oAs plate subducts, temperature increase causes water release from minerals in oceanic
crust
oWater causes melting in asthenosphere, causing magma to rise
oMagma erupts and can form island arcs (example: Alaska)
oMagma that solidifies at depth can add to the volume of the crust
oVolcanoes form too (example: Java, Indonesia)
- Ocean Continent plate
oSometimes volcanoes form the same way (example: Andes, South America)
- Continental collision forms mountain ranges
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- A transform fault is a fault that accommodates the horizontal movement of one tectonic plate
past another
- Biggest transform boundary: Pacific plate and North American Plate
- The movement of plate tectonics is a way of transporting heat to the Earth’s surface
- Plate tectonics: constant movement; asthenosphere becomes lithosphere, moves around then
goes down again through subduction zones
- What moves the plates?
oSlab pull: Ocean lithosphere (upper) is more dense than asthenosphere (lower) so
gravity pulls the plate down
oRidge push: Mid ocean ridge is more elevated than the sea floor because the lithosphere
is thinner and hotter at the ridge. Again, gravity causes the plates to slide away
oMantle convection: asthenosphere capable of flow, experiences convection.
- Hot spots: Convection of upwelling mantle material (rising mantle plume)
- Plate motions are detected using satellites and lasers
- Paleomagnetism: record of past changes in the earth’s magnetic field, as recorded in Earth’s
magnetic field
- Convection currents in the earth’s iron core causes magnetic fields to be generated
- Oceanic crust forms from upwelling magma then moves away from the ridge upon spreading so
the crust should be youngest at the ridge and older away from the ridge
Chapter 4
- A mineral must be naturally occurring, inorganic, crystalline solid
- Two types of rocks:
oCrystalline
oClastic
- You can distinguish minerals from their crytal shape, cleavage, fractures, color, luster and
microscopic observations
- We can test hardness, effervescence, streak and magnetism to help us identify a mineral
- Most nicely shaped crystals grow in an open space like water or magma
- Rock forming minerals:
oSilicates – Silicon and oxygen
oCarbonates – Carbon and oxygen
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oOxides – Oxygen bonded with a metal
oHalides – containing fluorine or chlorine
oSulfates – Sulphur bonded to oxygen
oSulfide – Sulfur bonded with a metal
oNative minerals – only one metal
- Light colored – felsic (quartz)
- Dark colored – mafic (amphibole, olivine)
- Nonsilicates : minerals that don’t contain silicon
- Most common nonsilicate minerals: carbonates and halides
- Oceanic crust: basalt, comprises of dominating plagioclase, pyroxene and olivine. Also contains
gabbro
- Most abundant element in the crust is Oxygen. Second most abundant is Silicon
Chapter 5
- Igneous rocks form by solidification of magma
- Most of the earth’s high internal temperature rises from the radioactive decay of unstable
atoms
- Geothermal gradient: temperature increase with depth
- Iron and nickel were pulled by the earth’s gravity towards the planet’s core
- Three mechanisms of heat transfer: convection, conducting and radiation
- Transfer of thermal energy via plate tectonics:
oAs solid asthenosphere rises, transfers hot rocks upward by convection
oConvection cell of seawater forms (water drawn into hot crust of mid-ocean ridge)
oNewly created lithosphere begins to cool by conduction
oCool oceanic lithosphere subducts into the asthenosphere again
- At higher pressures, it is more difficult for solid to melt into liquid
- Rock melting is influenced by three main factors: temperature, pressure and water content
- Temperature: increase in temperature can cause transformation from solid to liquid
- Pressure: Decompression (moving from high pressure to low pressure) can cause it to reach
liquid state (crossing the melting curve or solidus)
- Water content: the addition of water induces shifting of the solidus
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