Nifty mag

It's taken me a few years to realize something about American Scientist, a magazine I receive every other month. What struck me is that in every issue I learn something about a scientific topic that I thought I was up-to-date on, but in retrospect I was years (or decades) behind in my knowledge. So it has been great for keeping my broad science base from getting too stale.

For instance, the most recent issue has an article concerning plate tectonics. What do we remember about plate tectonics from high school science? Well, the big thing is that there are twenty or so different plates to the earth's crust floating around on the gooey magma deeper down, such that the continents move around relative to one another. A few hundred million years ago, all the continents had been jammed together into one big supercontinent ("Pangea") before splitting up. This all is still pretty much correct, says the magazine.

But what somehow had escaped my notice in the last twenty years were the discoveries that no fewer than six supercontinents have existed and broken apart through geological history. Going back in time from Pangea was Pannotia, Rodinia, Columbia (a.k.a. Nuna), Kenorland and Ur. I suppose that this shouldn’t be shocking – after all, why should continental breakup have only occurred in the last four percent of geologic time? I just hadn’t heard about this nor gave it any thought at all.

The big theoretical controversies now in this area concern exactly how this cycle proceeds. Do the continents spread apart, slow down, then reverse direction and slam back together? Or do they spread apart without stopping, and only slam back together when they’ve all reached the other side of the globe? Or is it some mix of the above? Catchy little article!