PHYS GEOG 2

• What is the order of the structure of the Earth? (chemical)


  Atmosphere (Continents), Oceans, Crust, Mantle, Core
• What is the order of the structure of the Earth? (physical)

  Atmosphere (Continents), Oceans, Lithosphere, "Moho", Asthenosphere, Lower Mantle, Outer Core, Inner Core
• Tell me about the Crust (chemical)

  • It is broken into Continental and Oceanic crust
  • forms the skin of the lithosphere
  • Thickness varies, ~3-5 miles
  • consists of Si O2 rich rocks (silica/silicon dioxide), granite & mafic
• What does the mantle consist of? (chemical)

  • ultramafic silicates
  • peridotite; dense rock w/ silicate minerals
  • Fe & Mg (Iron & Magnesium)
  • 80% of the Earth's total volume
• What does the core consist of? (chemical)

  • Fe (Iron), Nickel (Ni), and sulfur (S)
  • liquid outer region
  • solid core
  • 1/2 the diameter of the Earth
• What does the Lithosphere consist of? (physical)

  • It is along the crust & uppermost mantle
  • It is rocky & has a rigid crust
• What is the Mohorovicic discontinuity (Moho)?

  • Boundary between C.C and uppermost mantle
  • Earthquakes waves speed up when passing from crust to mantle; mantle is more dense than crust
  • MAKES IT POSSIBLE TO MEASURE THE THICKNESS OF THE CRUST; thickness can vary from 3-25 mi
• What does the Asthenosphere consist of? (physical)?

  • It is in the upper mantle; least rigid, susceptible to slow convection, cause by pockets of high heat
  • Partially molten or deforms fluidly like "plastic under pressure"
  • WEAK
• What does the Lower Mantle consist of? (physical)

  • Mesosphere
  • more rigid bc of great pressure
  • solid
• What is the Mesosphere? What is convection?

  It is above the stratosphere & below the thermosphere. Convection is the transferring of heat by the mass movement of a liquid; water, gas
• What does the Outer Core consist of? (physical)

  • Generates magnetic field which keeps us from being blasted from the radiation of the Sun
  • liquid phase, molten iron
• What does the Inner Core consist of? (physical)

  • Rigid
  • Solid iron & nickel
• What layer does the lithosphere float on?

  The Asthenosphere: plastic layer composed of semi-solid rock & it flows readily
• What is proxy data?

  You can't directly measure it (indirectly)
• What are some types of evidence for Paleoclimate?

  • Geological-glacial features & distributions; sediments
  • Biological-pollen, midden, coral, foraminifera, tree rings
  • Isotopes-O18/O16 ratio, c-14
  • Historical diaries, logs, legends, crop yields, art
• How would you describe Continental Crust? (sial layer)

  • Felsic, feldspar rich (granitic, silica, aluminum)
  • Light colored
  • Low Density; FLOATS
• How would you describe Oceanic Crust? (sima layer)

  • Mafic; Mg (magnesium) & Iron (Fe) rich (basaltic)
  • Dark colored
  • Higher Density; SINKS
• What was the old Plate Tectonic Theory?

  Global Contraction: James Dana (mid-late 1800s), Thermal Contraction
• What became the new Plate Tectonic Theory?

  Continental Drift: Alfred Wegener, movements of continents over the Earth's surface
• What is a summary of Alfred Wegener's (1915) theory/proposal?

  • Earth's crust is parted into a # of plates that move since they float on the asthenosphere
  • Continents seem fixed from human perspective
• What was Wegener's conclusion?

  The way the continents were configured are not the same as it was in the past: they were 1 SUPERCONTINENT called PANGEA ("All Land") 200-300 mya

  • Until mid-twentieth century, Scientists believed Earth's continents were rigid and Wegner couldn't determine what made plates move
• What was the evidence for Plate Tectonics?

  1. Continents/coastlines look like they fit together
  2. Similar fossils - flora & fauna
  3. a: Similar rocks - ages & chemistry; chemical fingerprints. b: MOUNTAIN CHAINS, 1 massive M.C; Appalachians (N. AM) & Atlas (N. Africa)
  4. Paleoclimatic Evidence; past glaciation
• Who proposed a mechanism to drive continental drift?

  Arthur Holmes: believed a fluid mantle possessed CONVECTION CURRENTS created by heat trapped beneath the Earth's surface
• What is continental drift?


  The movement of lithospheric plates
• What is the cause of Plate Tectonics?

  SEA-FLOOR SPREADING (Harry Hess, 1960s) This backed up Wegner bc the US Navy has data that helps explain plate motion
• How can you describe sea-floor spreading?

  • SLOW CONVECTION in Earth's mantle
  • Found in the magnetic properties of rock lying on the sea floor
• What can the slow convection is Earth's mantle do?

  • Push plates away from each other (Divergent Boundaries)
  • Slam into each other (ex: Cascadia)
• What are Midocean Ridges?

  The site of seafloor spreading leading to plate movement

  • magnetic reversals on either side of the ridge supports evidence for sea floor spreading
  • Formed by magma rising up from the mantle
  • New basaltic ocean floor is created, moves away form the ridge
• What is the process of Subduction?

  At the trenches, older lithosphere descends into the asthenosphere where it is recycled
• Describe Paleomagnetism


  Iron is magnetic and places itself w/ the magnetic poles of the Earth. It provides a record of past magnetic fields
• How many times does the orientation of the magnetic field change?

  170 times
• What does paleomagnetism & the magnetic field help with?

  We use this to know the age/time of the rocks
• What marks the location of plate boundaries?

  Earthquakes, volcanoes, & mountain ridges
• What are the 3 types of Plate Movement?

  Divergent, Convergent, & Transform
• Whats another name for divergent boundaries and how do they move?

  Passive; they move away from each other
• Describe Divergent (Passive) Boundaries

  • New crust is created and a mid ocean ridge occurs along it
  • Things happen more slowly and gentle
  • The asthenosphere wells up in the plate opening
• What do Divergent (Passive) Boundaries result in?

  Shallow-focus earthquakes & volcanic activity. It is constructive.

  • Continental rift valley, proto-ocean, starts on land
• What are the 3 R's?

  Ridge, Rise (Ocean, mid atlantic ridge) and Rift (Land, East African Rift)
• What makes the plates move apart in the Divergent boundaries?

  Tensional Forces
• What is rifting?


  Rising magma plumes w/in Earth, move upward & outward between plate fractures, which spread the plates apart