EARTH 7 Lecture 17: The K-Pg Mass Extinction
Document Summary
1980: walter and luis alvarez proposed that ~10 km diameter asteroid struck the earth: caused mass extinction. Idea primarily based on correlated, worldwide (big, 6-14 km) iridium anomalies. Despite this evidence, more than half of all american paleontologists at late as 1988 believed that extinction of the dinosaurs was in no way related to an impact. Instead believed in uniformitarianism (slow, gradual process explaining something) vs catastrophism: the smoking gun (1991, ~200-300 km-diameter crater dated to 66 ma. Impactor must have been >10 km: buried under >1 km of cenozoic sediment rock, first evidence was geophysical data from oil researches, lots of shocked quartz and presence of k-pg boundary. Many scientists still doubt that the chicxulub crater found in 1991 would be devastating enough to cause mass extinction. Comet shoemaker levy 9 headed for jupiter. Impact began july 16, 1994, and lasted for a week.
