Plate Tectonics: A Primer

I generally don’t do this, but this week a random conversation started up in the comments to my last After the Flood post. The issue at hand was evidence -- or, more appropriately, lack of evidence -- for a young Earth. After Da Bomb claimed he could offer evidence for Noah’s Flood, I challenged him to explain where all the water went. He offered this: “I thought this was interesting. http://www.christiananswers.net/q-aig/aig-floodwater.html.” I started to write a reply that’s turned out to be quite long, so I’m instead exercising my right as the guy who runs this blog and making a whole new post. So here we go… Um, I do hope you realize that any time you try to offer evidence for anything science related from Answers in Genesis you're not going to be taken seriously. But the article in question is easy enough to deal with. The article basically argues that there were no real surface features and that god lifted up the mountains and whatnot over the course of the flood in order to give them a place to drain. Yet we have absolutely no evidence of sudden, catastrophic planetary changes like that. What we do have is plenty of evidence to back up plate tectonics, which is indicative of gradual changes over time according to measurable, natural mechanics. What all the evidence points to is continental drift. Millions of years ago there was a giant supercontinent called Pangea that split apart. The Earth's is not a single, immobile piece of anything. It floats on top of what can be called, for lack of a better term, a sea of magma. There are also seams in the crust. The areas around those seams are constantly in flux. Some are expanding, some are contracting, and some are grinding past each other. Given these three types of plate movement and the theoretical supercontient, we should be able to expect to see a few things. First, we should expect to see some of the Earth's features that stretch across several continents. We have found that. The Appalachian Mountains, the island of Nova Scotia, the Scottish Highlands, and the mountains of Norway are all part of the same exact system. Go here and read the footnote. David Morgan-Mar explains it way better than I could. There's a similar formation where we know that the east coast of Brazil was joined to the west coast of Africa. Meanwhile, there aren’t any similar features between, say, China and California. This is because the point of expansion is the Mid-Atlantic Ridge. So the Americas are slowly drawing away from Europe and Africa and drawing closer to Asia. If we can wait a few million years, in fact, we’ll be able to see the formation of a new supercontinent as the Pacific shrinks to nothing. Second, we should be able to see evidence of rock formation and/or destruction on the edges of the plates. We can. The Mid-Atlantic Ridge is a giant mountain range in the middle of the Atlantic created a little bit at a time as magma pushes up through the center, gets to the top, and cools. On the other side the Pacific Plate is a subduction zone. As the North American Plate pushes against it, the Pacific dives underneath, where the rocks melt and basically allow for the cycle to start all over again. I find this video kind of annoying, but it’s a good primer. Back in the day I saw a video during an Earth Sciences class where they actually ran a video camera past the Mid Atlantic Ridge and watched magma flow up and cool. Sadly, I don’t remember what that video was called. Third, we should see consistent features around the edges of plates. Out in the Pacific Ocean there is an area known as the Ring of Fire, where volcanic activity is extremely high. When we look at the Ring of Fire we’re actually looking at the borders of the Pacific Plate. One of the best known features of the connection between the Pacific Plate and the North American Plate is the San Andreas Fault. This is what is known as a transform boundary, where the plates aren’t converging or diverging, but grinding past each other. Most of the time they more or less slide past each other. Every once in a while they get stuck and energy builds up at the boundary. When that energy is released we get earthquakes. Meanwhile, we don’t get that many earthquakes in, say Illinois, since there isn’t a transform fault anywhere nearby. Meanwhile, the Pacific Plate offers us further evidence of the movement of plates. Some volcanoes don’t form around plate boundaries, but over “hot spots” in the mantle where the Earth’s crust is locally thinner. We tend to see hot spots in the ocean, since ocean crust is much thinner than continental crust (for what I hope are obvious reasons). One of the best known hot spots is the chain of islands we call Hawaii. All of the Hawaiian Islands were formed from a single hot spot that pushed the islands up as the plate passed over. Now, then, what does plate tectonics have to do with mountains? You’ll notice that most mountains exist in ranges. The ones that don’t are generally volcanoes, too. The Rocky Mountains in North America arose due to compression of the continental plate. The Himalayas rose as the result of the collision between the Indian Plate and the Eurasian Plate. The Himalayas are still growing, since the Indian Plate is still moving north. The Rockies, on the other hand, are shrinking ever so gradually, since the forces that created them are no longer in effect and the main force active against them is erosion. Either way, the Rockies and the Himalayas have been around for 50 to 70 million years or so. So there you go. There are actual explanations for things. Answers in Genesis is an oxymoron…