Exam Review Flashcards

Five Questions For Exam

Search for life in the universe (i.e., suitable exoplanets)

• Ways to discover suitable planets:
  • Radial velocity method
  • Transit light method (most effective)
• Four categories of exoplanets:
  • Terrestrial
  • Neptune-like
  • Super Earths
  • Gas giants
• How we narrow down the search:
  • Circumstellar Habitable Zone (CHZ)
  • Mass of the exoplanet

Inorganic Carbon Cycle and Regulation of Atmospheric CO_2 over Deep Time

• The carbon cycle regulates atmospheric CO_2 over long timescales.
• Volcanism: Releases CO_2 into the atmosphere.
• Weathering: Draws down CO_2 from the atmosphere.

Leading Hypotheses of the Causes of the "Big 5" Mass Extinctions

Ordovician

• Late Ordovician Mass Extinction Interval 1 (LOME I): Occurred approximately 447 million years ago.
• Kill mechanism: Rapid drop in CO_2 due to biological deposition of organisms in reefs.
• Major Event: Weathering of the Appalachians significantly increased weathering rates.
• Huge decrease in CO_2 cooled the planet rapidly, faster than life could adapt.

Devonian

• Evolution of land plants: Specifically, trees with deep roots.
• Plants weather rocks and release phosphate.
• This causes global anoxia due to cyanobacteria blooms.
• Low oxygen and high hydrogen sulfide lead to euxinia.
• Increased weathering drives down carbon dioxide levels.
• Plants convert carbon dioxide into chemical energy for biomass formation, further reducing CO_2 levels.
• Low CO_2 leads to increased glaciation, which decreases sea levels.
• Decreased sea level causes reef die-off.
• Invasive species spreading may have slowed speciation as cratons came together, removing isolation among species.

Permian

• Formation of the Siberian Traps (Volcanism): Released massive amounts of CO_2, covering Siberia in flood basalts.
• Up to 2.5 miles thick in locations.
• Released 36,000 gigatons of carbon dioxide at a rate of approximately 5 gigatons per year over about 60,000 years.
• Evidence:
  • Carbon isotope 13 in sediments decreased.
  • Atmospheric carbon 13 decreased due to burning of fossil fuels.
  • The atmosphere had more carbon 12 than carbon 13 at the time.
  • Carbon 13 depletion serves as key evidence.
• Siberian traps formation led to a large increase in CO_2 in the atmosphere.
• Carbon dioxide in the atmosphere increased from 400 ppm to, at the highest estimation, 5000 ppm.
• Land temperatures jumped approximately 16 degrees Celsius (35 degrees Fahrenheit).
• Inner Pangea experienced heat waves up to 140 degrees Fahrenheit.
• Ocean temperatures jumped from approximately 25 degrees Celsius to about 40 degrees Celsius (104 degrees Fahrenheit, hot tub levels).

Triassic

• CAMP Formation: Pangea rifts apart into Gondwana and Laurasia, releasing massive amounts of flood basalts in a region called CAMP.
• CAMP formation released vast volumes of CO_2, increasing global temperatures.
• Ice decreased and sea levels rose.
• Evidence:
  • Igneous CAMP rocks found in eastern North America, South America, North and West Africa, and Southern Europe.
  • Delta carbon 13 ratio with carbon 12 reflects massive fossil fuels injected into the atmosphere.
  • Plant stomata density decreases, indicating more CO_2 was in the atmosphere.

Cretaceous

• Chicxulub Impactor:
  • Alvarez Impact Hypothesis, proposed in 1980.
  • Evidence: Anomalous iridium layer that is 30 to 160 times more iridium than surrounding layers.
  • 180 km diameter impact crater, asteroid size approximately 10-15 km (size of Mt. Everest).
  • Moving over 45,000 mph (12 miles per second).
  • Caused a massive fireball locally, forming plasma, flash igniting everything in the vicinity.
  • Earthquakes globally, around 10 to 12 on the Richter scale.
  • Raining ejecta globally.
  • Air blast knocks everything nearby down.
  • Tsunami hits.
  • Cold snap from aerosols, photosynthesis is knocked out.
• Deccan Traps:
  • Located in modern India.
  • Gerta Keller proposes this was the major cause of the extinction.
  • Most modern scientists believe it contributed to and was affected by the impactor but the impactor was the major cause of extinction.

Geological, Chemical, and Biological Evidence of Climate Swings and Mass Extinctions in Rocks

• Examples: Fossils, Lagerstatte, and Biogeography (fossil and extant species distributions).
• Evidence of biological responses to climate change:
  • Direct physical evidence of climate change in the last century.
    • Tree rings
    • Mismatch between consumers and their food source
    • Massive bleaching events for corals
    • Range shifts of organisms globally
    • Shifting in biological responses such as blooming, reproduction, and growth
• Paleoclimate proxies
  • Definition: indicators of past climate conditions
  • Examples: Deuterium, Sr/Ca ratio in corals (Past SST), and oxygen 18(temperature) as well as a proxy. Carbon 13/Carbon 14 ratios(provides insight on carbon cycle at the time, as well as temperature and plant photosynthesis).
• Lagerstatten: layers in which fossils are preserved extremely well and gives us a snapshot of the time period, as well as preserving organisms that wouldn’t normally be able to be preserved such as soft bodied organisms.

Causes and Ecological Consequences of Modern Climate Change

• Evidence of Modern Climate Change:
  • Direct physical evidence of climate change in the last century:
    • Phenological shifts in ice (to water, for instance).
    • Sea level rising.
    • Increasing ocean temperatures.
    • Increasing global temperatures.
    • Extreme weather events occurring more frequently.
    • Shifting precipitation patterns.
• Evidence of Biological Responses to Climate Change:
  • Direct physical evidence of climate change in the last century:
    • Tree rings
    • Mismatch between consumers and their food source
    • Massive bleaching events for corals
    • Range shifts of organisms globally
    • Shifting in biological responses such as blooming, reproduction, and growth