Chap. 8

  1. What is the oldest unit on the Geologic Time Scale? (hint: Eon)
    The Archean Eon; 4.6 billion years ago
  2. The Precambrian Period is comprised of what 2 Eons?
    • 1.) Archean Eon
    • 2.) Proterozoic
    • spans 87% of the Geologic Time Scale
  3. The oldest rocks that have been dated are meteorites
    4.6 billion years old
  4. The oldest dates of Earth rocks are detrital zircon grains in a sandstone in western Australia
    4.4 billion years old
  5. Earth’s oldest know crustal rocks, found in Canada
    4.4 billion years old
  6. Earth > Solar System > Milky Way galaxy > the Universe
  7. How old is the Universe?
    13.7 billion years old; big explosion (Big Bang)
  8. Solar Nebula Hypothesis (how solar system formed):
    Solar system distilled from a rotating cloud of dust, particles, and gases (called solar nebula)
  9. (Solar Nebula Hypothesis) Heavier material concentrated towards the center. created terrestrial planets such as:
    Mercury, Venus, Earth, Mars
  10. (Solar Nebula Hypothesis) lighter material at the periphery. Jovian plants that include:
    Jupiter, Saturn, Uranus, Neptune
  11. Chunks of rock from the Solar System that reach Earth's surface; include fragments of asteroids, moon rock, planets
  12. Earth's internal layered structure is composed of 3 actions:
    • 1.) Accretion
    • 2.) Shrinking due to gravitational compression
    • 3.) Differentiation
  13. Homogeneous conglomeration of space debris occurs during:
  14. Raises internal temp. to melt irons, nickel
    Shrinking due to gravitational compression
  15. Gravitational seperation, heavier materials toward center (forming core), light materials float out to form mantle/crust
  16. The Archean Crust
    magma cooled to form oceanic crust (komatiites-basalt); partial melting of basalt at subduction zone created first continental (i.e. granitic) crust
  17. Earth has 2 types of crust today:
    • 1.) Dense, mafic (Mg, Fe) oceanic crust dominated by basalt.
    • 2.) Less dense, sialic (Si, Al) continental crust dominated by granite
  18. Today we are adapted with air that has 21% oxygen
    Earth's first atmosphere lacked free oxygen. Evidence: lack of oxidized iron in the oldest sedimentary rocks
  19. Early Ocean: formation of hydrosphere in 2 steps:
    • 1.) Volcanic outgassing released water-vapor into the atmosphere
    • 2.) Water-vapor condensed and fell as rain to form seas
  20. Having outgassed all the water early in history, Earth has been recycling it ever since via the _____ cycle
    Hydrologic cycle (evaporation, condensation, rain, etc).
  21. Free oxygen started to appear after 3.7 billion years ago when photosynthetic prokaryotes appeared
    Oxygen was abundant in the atmosphere around 2.5 billion years ago– when photosynthetic eukaryotes evolved
  22. The earliest evidence of life occurs in 3.5 billion year old sedimentary rocks
    Stromatolite, an organo-sedimentary structure; Microscopic cells of prokaryotes, photosynthetic cyanobacteria, or blue-green algae
  23. Life may have also originated at midoceanic ridges because:
    Nutrient-rich, heated water supports chemosynthetic bacteria
  24. The earliest organisms that developed in the atmosphere which lacked oxygen:
    anaerobic prokaryotes. unlike photosynthesis, energy is produced by chemosynthesis
  25. Later evolved photosynthetic prokaryotes
    use photosysthesis to produce energy and oxygen as byproduct
  26. Finally evolved eukaryotic cell, which could cope with oxygen in the atmosphere
Card Set
Chap. 8
geo test