Lecture 19: Extinction

Question 1

chicxulub crater

Answer 1

crater in the yucatan peninsula
- about 110 miles in diameter and ~12 mi deep
- evidence of shocked quartz that were deformed by high pressures like in a giant explosion and tektites
- in 1990s: the impact was dated to ~65M years

Impact:
- fiery plume from the impact reached halfway to the moon
- material from the Earth likely reached the moon, and possibly mars
- infra-red radiation pulse from kinetic energy released
- atmosphere within 1500 miles of ground 0 became red hot from the debris storm, triggering global fires
- ~70% of world’s forests were consumed
- asteroid vaporized layers of limestone, releasing trillion tons of CO2, 10 billions of methane, and a billion tons of carbon monoxide
- also vaporized anhydrite rock, blasting trillions of sulfur compounds into atmosphere => combined with water to make acid rain that may have been potent enough to strip leaves from any surviving plants and to leach nutrients from soil
- 75% of fossil species went extinct

Question 2

Cretaceous - Paleogene extinction (K/Pg)

Answer 2

killed out many types of dinosaurs, some birds survive but many don’t
- hadrosaurs/ornithopods
- Ankylosaurs
- Sauropods
- Ceratopsian
- Pachycephalosaurs
- Pterosaurs
- Mosasaurs
- Therapods

Question 3

Deccan traps

Answer 3

cretaceous, igneous flood basalts (Igneous rock)
- 6,600 ft thick in some places => 200,000 sq mi
- 66.25-66M years (30,000 years of eruptions)

Question 4

Hell creek formation

Answer 4

late cretaceous North America
- about 66Mya

Question 5

Iridium

Answer 5

• iridium layers spike at the K/PG boundary
• Luis Alvarez suggested that the level of Iridium might determine how quickly the clay layer is an element
• an element deposited from cosmic dust at a fixed rate
• amount found to be 9 parts per billion, 90 times higher than anticipated over natural production
• led to hypothesis of an asteroid impact

Question 6

signor-lipps effect

Answer 6

as you get closer and closer to the mass extinction event, it looks like diversity is disappearing

Question 7

tanis

Answer 7

• a fossil site from North Dakota described in 2019
• shockwaves from the impact washed river animals ashore
• might have evidence of diverse dinosaurs as well, which could resolve the dinosaur “slow death” hypothesis
  
  • not yet published in scientific journal

Question 8

tectites

Answer 8

natural glass formed from terrestrial debris ejected during meteorite impacts

Question 9

mass extinction events

Answer 9

a widespread and rapid decrease in earth biodiversity
- 5 mass extinction events
- late ordovician, late devonian, permo-triassic, triassic- jurassic, cretaceous - tertiary
- background extinctions:
- predation, competition, disease -> species with small population sizes are at greater risk
- changes in environment => specialists are at greater risk than generalists