Evidence for Asteroid/Comet Impact
Iridium Spike (Walter Alvarez et al.)
Fireball layer (65 Ma)
Crater (1992 Ð Chicxulub, NW Yucatan Peninsula)
Evidence for Giant Volcanic Eruption
India Ð Deccan Traps (500,000 sq. km, up to 2 km thick)
Started before, lasted 2+ My
1. How do each of the following provide evidence of a major asteroid (or comet) impact, 65 Mya?: iridium spike; shocked quartz; tektites; Chicxulub.
2. What are the Deccan Traps? What are plume tectonic events and how common are they? How long do they last, including lingering hot spots?
3. What are some of the scenarios for extinction caused by a catastrophic asteroid impact? How might each affect organisms present?
4. What are some of the scenarios for extinction caused by catastrophic volcanic activity? How might each affect organisms present?
5. Describe an alternative scenario based on a more gradual oceanographic/climate change. What evidence might support this alternative explanation for extinction?
6. Why, if we are relatively certain that an impact occurred, is the problem of what caused the major extinctions still unresolved? What are some difficulties remaining with asteroid or volcanic catastrophe scenarios?
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