Earth

Cards (9)

  • Earth
    • 3rd place from the Sun
    • Only known body in solar system with plate tectonics
    • Liquid water at surface
    • Biosphere
  • Earth is similar in size and diameter to Venus
  • Earth's temperature is moderated, which is why it is habitable
  • Internal Structure of the Earth
    • 3 main layers: Crust, Mantle, Core
    • Seismic waves are reflected and refracted as they pass through the Earth
    • Velocity of waves depends on modulus and density
    • Used to map changes in density with depth
  • Mantle Transition Zone
    • Marked by a seismic velocity discontinuity
    • Olivine undergoes phase transitions between 440 - 660 km
    • At 660 km, olivine transforms to perovskite
  • Seismic Shadows Zones
    • Discovery of the Core(s)
    • Earth's core acts like a prism, causing S-wave shadows
    • Richard Oldham discovered the outer core in 1906
    • Harold Jeffreys found S waves do not pass through the outer core in 1926
    • Inge Lehmann recognized waves reflected from a boundary deep within the Earth, outside of the inner core, in 1936
  • Oceans
    • Cover 71 percent of Earth
    • Average depth ~4.2km
    • Mariana trench ~11km deep
    • Pressure increases 1 bar every 10 m depth
    • Average temperature ~2 celsius
    • Only ~5% of ocean floors explored
    • We know more about the topography of Mars
    • ~50 - 80% of all life resides in the oceans
  • Earth's Atmosphere
    • Nitrogen (78%), oxygen (21%) and argon (1%)
    • Trace amounts of other gases
    • 4 main layers: Troposphere, Stratosphere, Mesosphere, Thermosphere
    • Ionosphere is extension to space
    • Contains ~80% of atmosphere
    • Rapidly thins upward
  • Milankovitch (Orbital) Cycles
    • The shape of Earth's orbit (eccentricity, 100,000 year cycles)
    • The angle Earth's axis is tilted with respect to Earth's orbital plane (obliquity, 41,000 year cycles from 22.1 to 24.5 degrees)
    • The direction Earth's axis of rotation is pointed (precession, 26,000 year cycle that wobbles like a spinning top)
    • These control when we get ice buildup at high altitude and hence periods of glaciation and interglacial