Geology, Pangea, Marsupials

"What's Going Down in Geology"

"What happened to the Big Marsupials of Australia, what does that have to do with the simultaneous rise and fall of the Sierra Nevada?" was the question on Thursday, in room Science-422.

Geology instructor Roger Chambers went on to ask: "What's your favorite Marsupial?" to break the ice and show how little we, the audience, actually knew about them. I personally was not aware that Australia was a devastated ecosystem built around them. He, like many experts believes that it was unlikely that they got to Australia via swimming from Asia. What he did believe was that they migrated throughout one the world's super-continents of the past Gondwana approximately 200 million years ago. The time of the giant birds ended and the marsupials expanded. Unfortunately by 45,000 years ago 90% of the marsupials had been hunted to extinction by placental mammals. Chambers proposed that marsupial's current state was the result of geological events rather than just a biological or evolutionary one. The separation of Australia from the rest protected them, allowing them to escape to refuge and continue development.

As an example of this geological history, we have King's Canyon here in California, which is a result of the surrounding mountains uplift. This ties into Plate Tectonics theory as well as Continental Drift hypothesis. The more northern Sierras are rising, and the southern sinking, while the plains are also sinking and being pushed farther out from the mountains. Possibility is that "Mantle-Drip Hypothesis" is going on, the idea that the mountains roots have detached and are gradually sinking into the Mantle. Cave studies (speleology), he cited, are shedding new light on the past in the region of continental divergence. Also, new techniques have been devised to gauge a caves "age" through dating the last time sunlight struck the boulders inside. Stalagmites have been found to show signs of climate, much like a tree ring shows a tree's age, throughout its development. "Chutes" have been found where biological life as well as geological matter has fallen into holes in the ground, created by shifts in the earth, serve as time capsules into a spectrum of natural history.

I found this presentation to be very informative,