How long will it take for California to collide with Alaska?

Answer 1

California and Alaska share the North American plate. But a bit of California, that is, a slice of it cut into the state near San Francisco and going south to the Gulf of Mexico, is on the Pacific plate. That bit of what is currently the California coastline, including the islands offshore in what is now Southern California are headed toward Alaska. It might be more accurate to say that the North American plate is moving south. Whether that bit of California will still be above the surface when they get there, we don't know. But there's a catch. (There's always a catch.) The Pacific plate is moving under the North American plate. What this means is that as those little bits of California move north (or the North American plate is moving south), they are also moving east and under the North American plate. That's because there is a big split down the middle of the Pacific plate (called the Pacific rift zone) that is pushing some of the Pacific plate east. There is a subduction zone which is offshore and runs along the western U.S. from northern California up past Oregon, Washington and along a bit of British Columbia. The end result is that there may not be any bits of California left above water by the time that portion of the Pacific plate reaches the Alaska area. But let's do the math (which is all we can do since we don't have a crystal ball). The plates are moving at a relative speed of about 5 centimeters per year (5cm/yr), so let's assume it stays constant. There are some 1200 kilometers (1200 km) between California where the fault comes ashore and the souther tip of Alaska (ball park figure). In case you don't have a calculator handy or can work it in your head, it's gonna take about 24 million years for California to get to Alaska, give or take a few. You just gotta wonder what the earth is gonna look like that long from now! If you look below, there is a smokin' link (SciLink) to a post that has lots of killer information and super illustrations. You read that and you'll become an expert in plate tectonics overnight! Go read it. Dare ya!