Plate Tectonics and GPS

I don't know how much you may have thought about plate tectonics.  Plate tectonics is the current theory of how our world's land masses interact, form mountains, create earthquakes, etc.  The idea is that the outer crust of out planet is not whole but made up of many large plates that float on the mantle.  I have seen references in news articles and never gave it a lot of thought.  Today I saw an article (see link) in the U of M news service that talked about the subject.  In that article, the author, quoted University of Michigan geophysicist Marin Clark,  Ms. Clark noted that the plates are moving at roughly the rate fingernails grow.  While I cannot quote you a rate for that in any sort of units per unit time, that is pretty fast and measurable.  I wondered if anyone was looking at this using GPS.


Well, Google "Plate Tectonics and GPS" and you will see that there is a huge body of data supporting motion of the places we live.  The good old earth and our properties are moving, a lot.  NASA has compiled a lot of data on this and has the data and a nifty slide show (see link) available.  Look around the map where individual sites are marked.  Each site on the world map there represents a reporting station with a high-quality GPS receiver.  The lines attached to each of the points represent the direction and velocity.  I would drop a copy of the map in here but the use is covered by a Google use policy that is not entirely clear.  The data, however, is from NASA's JPL and can be used here.  I noticed that the vectors for Australia were quite a bid longer than most and looked at the data for "ADE1" (see link), a station on the southeast coat of Australia near Adelaide.  The latitude is noted as changing an average of 58.5 mm/year.  For those not familiar with the metric system, that is over 2 inches per year!  Most of the continental US is moving at a much slower rate but the data shows that our positions are moving around at 3/8 to 2 inches per year depending upon where you live.  


I suspect the average 6th grader has already been introduced to this but for most of us, this is a surprise.  While I knew that the various plates were moving, I had no idea how much.