Pangaea - the idea of Pangaea and some of the evidence behind it. I did not know that Pangaea was not the first super-continent, but that this coming together and breaking apart process has been ongoing for millions of years. Of course!
I am loving the Kahn Academy. With a library of over 2,700 videos covering everything from arithmetic to physics, finance, and history and 247 practice exercises, they're on a mission to help you learn what you want, when you want, at your own pace. www.khanacademy.org