The Dynamic Earth
� CORE
Earth�s Internal Zones
� 1/2 radius
� 2 parts
� 16% volume, but 31% of mass
� inner core - solid, mostly iron, 3400C 3,000,000G�s gravity
� outer core - liquid, 3700-4300C
� MANTLE
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solid
10-2900km from surface
82% of volume, but 68% of mass
iron, plus O, Si, Mg
low velocity zone
� upper part of mantle
� semi-liquid (1-10%)
� seismic waves slow down
� asthenosphere
� CRUST
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Earth�s Internal Zones
Earth�s Internal Zones
thinnest section
2% volume, 1% mass
10-65 thick
earthquakes are generated
plate movement
lithosphere
Composition of Earth�s Crust
Types of Crust: Oceanic
� 71% of surface, dense, 10km thick
� oceanic ridge system
� 80,000 km long
� 1500-2500km wide
� 2-3km wide
� Abyssal Floor
� deep ocean basins, 5km below sea level
� trenches
� 8 km below sea level
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Continental Crust
Higher and thicker than oceanic crust
averages 35km thick
lower density--> floats
continental shelf- underwater portion of the continental crust
Crust Plates
� 100km thick (crust and mantle) - lithosphere
� move over the semi-liquid asthenosphere
� move at the same rate as finger nails grow (1 inch/year)
Plate Techtonics
� Theory that explains the apparent movement of Earth�s plates and
the geological process that occur at the boundaries
� The movement of the plates
� is an explain the biogeography of organisms
� is responsible for the earth surface features
� concentration of minerals
� Evidence
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Plate Techtonics
polar wander curves
distribution of organisms
distribution of ice
shape of continents
continued activity at boundaries
Plate Boundaries
Divergent Boundaries
� Plates move in opposite directions
� ocean spreading
� creates ridge
� youngest area of ocean
� earthquakes and volcanoes
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Convergent Boundaries
Plates move toward each other
often: oceanic plate is subducted under continental plate
subduction zone makes a trench
earthquakes and volcanoes
oldest part of ocean
Transform Fault
� Plates move in opposite, parallel directions
� San Andreas
� only earthquakes
External Processes:
Break Down Earth�s Surface
� Erosion
� material is broken down, worn away, and moved
� streams are primary source
� also wind and gravity
External Processes:
Break Down Earth�s Surface
� Weathering
� mechanical - a large rock is broken down into smaller rocks (frost wedging)
� chemical - a rock is decomposed by chemical reactions (oxidation, acid rain,
hydration)
External Processes:
Break Down Earth�s Surface
� Mass wasting
� large amounts of material are carried downhill by gravity
� rock slides
External Processes:
Break Down Earth�s Surface
� Glaciers
� solid, dense ice
� moves downhill, carving as it goes
� carries material (leaves moraines)
External Processes:
Break Down Earth�s Surface
� Human Activities
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clearing land and vegetation
over grazing
mining
off-road vehicles
Rock Types: Igneous
� Rocks formed by molten rock (magma)
� made at plate boundaries
� below surface
� crystals, gem stones
� eg. granite
� above ground
� lava, no crystals
� eg. obsidian, pumice
Rock Types: Sedimentary
� Rocks formed from sediments, other rocks
� A. small rocks carried by water
� sandstone/shale
� B. compaction of dead animals
� limestone
� C. decomposition of plants
� coal
� *3/4 of Earth�s surface
Rock Types: Metamorphic
� Rock formed when a pre-existing rock is subjected to extreme heat, chemicals
and/or pressure
� eg. marble, talc, graphite, slate
The Rock Cycle
Mineral Resources
� Minerals: naturally occurring materials in or on the crust that can be
extracted and converted into useful materials
� *within the scale of human activities they are nonrenewable because
of the slowness of the rock cycle
� energy resources: coal, oil, uranium
� metallic resources: iron, copper
� nonmetallic: salt, clay, water, sand
� Identified
Categories of Mineral Resources
� known location and quantity
Categories of Mineral Resources
� Undiscovered
� believed to exist, but location unknown
� Reserves
Categories of Mineral Resources
� identified resources that can be extracted economically
Categories of Mineral Resources
� Other Resources
� identified, but not economical, and undiscovered
� may become reserves