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