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. Let’s not forget, though, that the basic scenario of the impact hypothesis is supported by most scientists.
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.
For the extraordinary story about the end-Cretaceous extinction deposits recently described in North Dakota, first read this BBC account, which is typical of the hundreds of news stories about the finds. Next read this long but entertaining story in The New Yorker. Finally for a more mixed (and realistic) appraisal, read this news article in the journal Science. It is becoming a fascinating scientific and cultural narrative. The actual PNAS paper is linked here. [Update: Another perspective on this story.]
Remember: Review sessions every Friday, 3:30 – 4:30 pm, in Scovel 205.
Geology in the News –
Here’s the best account I’ve found describing the marvelous image of a black hole revealed last week. An historical moment. If you’re not impressed it is because you don’t understand the gravity of the situation.
And then there’s a new extinct hominin in the Philippines! Homo luzonensis lived between 50,000 and 67,000 years ago on a Philippine island. Let”s watch how this story develops.
Finally, and it sounds now so prosaic, there are some newly discovered dinosaur skin impressions. Early Cretaceous of South Korea.