Posted by jlwile on April 30, 2012
In the theory of plate tectonics, the earth’s surface is broken into several distinct plates which move about, carrying the continents with them. As a result, a fixed location on the planet is not really stationary. It is actually moving along the earth! We don’t notice the motion, of course, because it is happening very slowly. However, according to the theory, it is always happening. If scientists make certain assumptions about how this motion occurred in the past, they can conclude that at one time, all the continents on earth were grouped together in a supercontinent called Pangaea. Over time, the motion of the plates then separated the continents into the positions we see today.
If you assume that the plate motions we think are happening today are representative of how fast the plates have always moved, you find that it would take hundreds of millions of years for the continents to have moved from Pangaea to where they are today. However, many young-earth creationists think that plate motions were much faster during the worldwide Flood, and some have produced detailed computer models that attempt to explain how the Flood happened in the context of this catastrophic plate tectonics. Other young-earth creationists are skeptical about plate tectonics, claiming that there isn’t a lot of evidence to support it.
I tend to disagree with the young-earth creationists who are skeptical about plate tectonics. While I am definitely not a geologist or geophysicist, I do think there is a lot of indirect evidence to indicate that the plates are real and that they are really moving. Interestingly enough, I recently ran across an article by Dr. John Baumgardner that, in my mind, really clinches the case for the reality of plate tectonics.1 Not only that, the data used in the article are just plain cool!
It turns out that the Global Positioning System (GPS) has been monitoring over 2,000 stationary receivers that have been placed all over the earth. The GPS confirms that these receivers are moving at surprisingly constant velocities, despite the fact that they are fixed to the ground. The map shown at the top of the post, for example, displays several of the receivers and the directions in which the GPS confirms that they are moving. If you go to the Jet Propulsion Lab (JPL) website that archives these data, you can look at any part of the world and see the receivers that are there and how they are moving. If you do that, you will find that they are moving the way you would expect them to move in the context of plate tectonics.
What’s really fascinating to me about these data is how detailed they are. For example, some of the fastest motion detected by the GPS is around Australia and New Zealand. Let’s look at the GPS data for a receiver that is sitting on the Cook Islands, which are in the Western Pacific, east of Australia:
The black dots are the data, and the red lines are simply meant to guide your eyes along the data. Note that the graphs span a bit more than ten years. In that time, the receiver has moved about 36 centimeters in latitude and about 60 centimeters in longitude. Its elevation, however, hasn’t changed significantly. Now look at the data points themselves. Notice that for both longitude and latitude, most of the points fall along an almost perfectly straight line. There are a few deviations here and there, but the straight lines are unmistakable. Physics tells us that the slope of a position versus time curve tells you the speed. Since a straight line has a constant slope, the straight lines in these graphs tell us that the speed at which the Cook Islands are moving has stayed remarkably constant over the past ten years.
I just think it is nothing short of awesome that we have these data!
1. John Baumgardner, “Is Plate Tectonics Occurring Today?”, Journal of Creation 26(1):101-105, 2012
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