The story of the Cretaceous Mass Extinctions is amazing. The “Impact Hypothesis” was developed at the University of California, Berkeley, in 1980 when I was there as a graduate student (to my great fortune, even if I had nothing to do with it). It seemed a real stretch at the time, but now we know it as one of those intellectual breakthroughs which changed our perspective on the History of Life. The Wikipedia page on the Cretaceous Extinctions is very good and kept updated by experts. The Sam Noble Museum has a good executive summary of the extinctions. In 2010 an Independent Study student (Megan Innis) and I had a great time at the Cretaceous-Paleogene boundary in Alabama and Mississippi.
We will emphasize the Impact Hypothesis in this course because I think it is the one best supported by the evidence. If you like your extinctions via YouTube, watch these Discovery Science videos, part 1 and part 2. The volcanic hypothesis is still alive, although on life support. Here is a nice summary of the most recent attempts to link volcanoes to the Cretaceous extinctions. In contrast with these reasonable (more or less) disputes, there are many more exotic ideas about dinosaur extinctions specifically, some tallied here and here. The Great Chicxulub Debate hosted by the Geological Society of London was several years ago, but the arguments are worth visiting. Let’s not forget, though, that the basic scenario of the impact hypothesis is supported by most scientists.
Here is the Fall 2017 Final Exam description. (Test seating: Students with last names starting with A through H in Room 205; I-Z in Room 216.) Even though the final is about a month from now, you’ll want to start studying. Those superquizzes will be your encouragement!
Remember: Review sessions every Wednesday, 3:30 – 4:30 pm, in Scovel 205.
Geology in the News –
The end-Cretaceous asteroid impact may have had an even more dramatic effect on climate than we thought (and that was pretty bad). I notice here that the asteroid is now expanded from 10 to 12 km in diameter. Here’s a BBC account of the same research.
A new great ape species has been identified in Indonesia. This doesn’t happen often!
Here’s a good article on the problems inherent in defining biological species. Evolution is at the species level, but we have difficulty grasping a concept of species.