Structure of the Earth
Compositional (Chemical) Layers Crust: Low density Moho: Density boundary between crust and mantle Mantle: Higher density High in Magnesium (Mg) and Iron (Fe) Core: High in Nickel (Ni) and Iron (Fe)
Earth: The Giant Magnet Magnetic field created by liquid iron convection in outer core.
Magnetic field directs solar winds (ionized particles) around the Earth or to the poles.
Aurora Borealis
Heat Flow in the Earth Heat sources: Latent heat from the formation of the Earth Temperature at core: 3000-5000 C Cooling processes: Plate tectonics (volcanoes)
Mechanical (Physical) Layers of the Earth Lithosphere: Crust and upper, part of the mantle; plates in plate tectonics (lithos = rock) Asthenosphere: Partially molten part of mantle; Outer core: Liquid Inner core: Solid Greatest temperatures Solid due to
Evidence for Structure of the Earth Seismic (earthquake) waves P waves (Primary): Longitudinal (compressional) waves; faster, can move through any matter S waves (Secondary): Transverse waves. Can only travel through solid matter.
Major Plates on Earth
Ring of Fire: Plate Tectonics Earthquakes & volcanoes are distributed mostly in bands along the Earth's surface. These bands correspond to tectonic plate boundaries.
What Drives Plate Tectonics? Convection currents in the asthenosphere driven by the heat Where currents rise,
Discuss with your table partner: Review the definition of the word viscosity. Predict how the viscosity of magma affects whether a volcano will be more or less explosive..
Discuss with your table partner: Factors that affect viscosity of a substance of a substance include o The chemical composition Silica is a substance that increases the viscosity of magma. It has a light color. o The temperature How does increased temperature affect viscosity? Compare the viscosity of cold vs. warm syrup.
Discuss with your table partner: Predict how the magma viscosity and explosiveness of volcanoes relates to their typical shape. Which type of eruptions would produce more cone-shaped volcanoes (stratovolcanoes) vs. flatter shield-shaped volcanoes?
Volcano Video http://www.youtube.com/watch?v=jrfegvp6wdu
Divergent Plate Boundaries Plates moving apart due to rising magma below. New oceanic crust is formed Undersea mountain chain is created: mid-ocean ridge Widens existing oceans or creates new ones (Red Sea, Great Rift Valley in Africa)
Evidence of Sea Floor Spreading rock found at mid ocean rift. Periodic reversals of the polarity of the Earth s magnetic fields..
Divergent Plate Boundaries The Red Sea is a newly forming ocean The rift valleys in Africa are splitting it apart
Hydrothermal Vents at Divergent Boundaries
Convergent Plate Boundaries Plates moving towards each other. Differing densities of plates affects outcome Three Types: Ocean-Ocean collision Ocean-Continent collision Continent-Continent collision
Discuss with your table partner: Ocean plates are generally more dense than continental plate. Predict what happens when an ocean plate and a continental plate collides. (Is there uplifting of both plates, or does one plate get subducted (pushed under the other plate). If subduction occurs, which plate is subducted and why?
Ocean-Continent Collisions Ocean crust gets because it is denser and Explosive volcanoes form on continental plate Volcanoes are approximately the same age and are cone-shaped stratovolcanoes Trench is formed off the coast Mt. Shasta
Accretionary Wedge: Forms when, so it piles up in front of the upper plate Accretionary wedges are non-volcanic Example: Olympic Peninsula
Ocean-Ocean Collisions Older, denser ocean plate gets subducted and melts Deep trench is formed by bending of downward plate Chain of volcanic islands is formed = Island Arc. Example: Japan Volcanoes are explosive due to sediments (silica-rich) subducted with ocean plate. Stratovolcanoes (cone) Mineral rich hydrothermal deposits can occur
Discuss with your table partner: At convergent boundaries between two continental plates there is uplifting rather than subduction. Try to explain why uplifting rather than subduction occurs at these boundaries. Predict whether the mountains in these locations would have o stratovolcanoes (explosive) o shield volcanoes (gentle) o not be volcanic
Continent-Continent Collisions Continental crust is, so very tall mountains are produced by uplifting Himalayas are still rising Older examples: Alps Appalachians
Plate Boundaries Video http://www.youtube.com/watch?v=0mwqs1_l3fa
Transform Plate Boundaries Plates slide in Transform faults occur usually this occurs between different segments of midocean ridges Earthquakes are common Example: San Andreas Fault (CA)
Transform Boundary Animation http://www.youtube.com/watch?v=tiuk2blbzhs
Hot Spots Deep magma source stays stationary as plate moves over it. Hot Spots under oceanic plates (i.e. Hawaii) Hawaii
Hot Spots: Ocean Hot spots erupting through ocean crust erupt only basalt -Eruptions are nonexplosive -Volcanoes are type Mauna Loa
Hawaii Hot Spot Video http://www.youtube.com/watch?v=hocfb9ox_90
Hot Spots: Continental Hot spot can melt portions of the continental crust ( ), causing Hot spots can have very active hydrothermal circulation, which will produce metal ore deposits Deccan Traps
Discuss with your table partner: When magma erupts (as lava) does it cool more slowly or more quickly compared to magma that solidifies while underground? Predict how the speed at which a mineral solidifies affects the number/size of the crystals that are able to form.
Rock Types Igneous Rock: 2 types of Igneous o Extrusive (volcanic) = erupted lava Cools o Intrusive (plutonic) = never erupted magma
Extrusive Igneous Rock Basalt Andesite Rhyolite Low in silica Black High in Silica Pale pink, grey
Intrusive Igneous Rock Gabbro Dacite Granite Low in Silica Black High in Silica Pale Grey, pink
Sedimentary Rock Sedimentary rock: formed by compaction of sediments.. Shale Sandstone
Metamorphic Rock Metamorphic rock is rocked that has been. Caused by burial and proximity to volcanic areas. Many gemstones are metamorphic.
Discuss with your table partner: Which kind of rock could contain fossils. Why? Predict which type of rock would tend to be the densest and often have folds. Why?
Rock Cycle