by Pat Darnell
Bryan TX | 04.03.2010 | Originally I thought the continents were moving around the globe at a very slow rate. Then, the other day on History Channel, it comes to light that the North American Continent is moving rather rapidly -- in Geologic Time... [whatever that means...]. Paleogeography is plate distribution over time.
PHOTO Left :: Time-exposure photograph of the electronic-laser, ground-motion measurement system in operation at Parkfield, California, to track movement along the San Andreas fault (Photograph by John Nakata, USGS.)
Regardless of the changes that will affect us in the next century, the plates will continue their journey. Small as the displacement may seem ... the plates move at about the rate that your hair grows ... , the forces generated are very large and the natural hazards that they produce will remain to be enormous. There's no messing with nature in the long run. (edu umich. HERE )Others I know have been led to believe that the world is "more" than "less" like it has always been in Human time of our inhabitation of continents. So imagine my surprise.
Alfred Wegener's theory on continental drift, published in 1915, remains to be the interpretative force behind the field of tectonic plates and oceanography. In his book, The Origin of Continents and Oceans Wegener supported a previously debated idea of continental drift, explaining that a supercontinent he called Pangaea (i.e., all lands), once existed in the past, then dismembered.
This breaking-up process started some 200 million years ago, and, the pieces "drifted" into their present positions around the globe. Wegener called attention to the fit of Atlantic rim of South America and the western rim of Africa, along with similarities in ancient climate, fossils (such as the fern Glossopteris and mesosaurus), and the similarity of rock structures. (Johnson, Charles William. 2001-2009 Copyrighted by Charles William Johnson. Retrieved HERE: Was Wegener Wrong? Tectonic Plates, Continental Drift and The Symmetry of the Continents Part One)Trinity University in 1975, Geology Professor Gannon told us Mug-Wump Sophomores that "there were thousands of theories of tectonics... with about 700 theories gaining popularity." That alone told me that the future was not just around the bend, if I was to understand global continental drift. In 1975 Tectonics was still only a theory. So be it.
Today, my kids learn continental drift tectonics as a by-line in eighth grade geography. HA! Check out this site where you can build your own model: ODSN Plate Tectonic Reconstruction Service. [See: also This Dynamic Planet]
"Yeah, Dad, so what?" they say to me if I bring it up.
"It is difficult to suggest that the continents do not drift, or that the dozen or so tectonic plates that make up the Earth's surface do not collide. In fact, today's sophisticated, technological research findings reveal that continents and plates do collide producing mountain ranges, earthquakes, and many other manifestations in the geography of the Earth. The continental drift or shift is cited as representing a yearly movement of between 50mm and 90 mm. In terms of absolute measurement, that amount appears to be insignificant; in terms of geological time, the distance can be enormous..." (ibid)South America east coast appears to fit right into Africa's west coast. Evidence on each other's coast shows similar deposits of minerals and geologic formations, as if split apart from an imaginary super size land mass.
"... [W]e shall not consider whether there is or is not movement of the continents, which appears to be empirically confirmed, but rather, how might that motion be interpreted as of the maps offered by different scientific sources today." (ibid)Study of magnetic material originating from the ocean floor shows empirical data that the continents slide.
"Crucial to accepting the concept of steadily moving plates was the discovery in the 1950s that the Earth's magnetic field has reversed its polarity hundreds of times in the last 100 million years and many more times before that. As lava solidifies at ocean ridges, it becomes magnetized according to the polarity of the Earth's magnetic field when magnetic minerals pass through a particular temperature range (the Curie point; ~480C in magnetite). If the field's polarity is reversed, the basalt is magnetized in an opposite sense. As the ocean floor moves away from the ridges, these magnetized strips of rock are carried away on either side like a conveyer belt. This process is remarkably similar to that used in a magnetic tape recorders. (edu umich. Regents of the University of Michigan retrieved today HERE)"
"The layers of the Earth can be described in terms of their physical properties (e.g., lithosphere and asthenosphere). The behavior of seismic waves is dependent upon the phase of the material as well as its temperature. The patterns of the velocity of seismic waves through the Earth's interior provide us with a physical interpretation of the crust, mantle, and core as well as the location of the boundaries between these layers."Last Word
"The long-term benefits of plate tectonics should serve as a constant reminder to us that the planet Earth occupies a unique niche in our solar system. Appreciation of the concept of plate tectonics and its consequences has reinforced the notion that the Earth is an integrated whole, not a random collection of isolated parts. The global effort to better understand this revolutionary concept has helped to unite the earth-sciences community and to underscore the linkages between the many different scientific disciplines. As we enter the 21st century, when the Earth's finite resources will be further strained by explosive population growth, earth scientists must strive to better understand our dynamic planet. We must become more resourceful in reaping the long-term benefits of plate tectonics, while coping with its short-term adverse impacts, such as earthquakes and volcanic eruptions." (Watson, JM. http://pubs.usgs.gov/publications/text/tectonics.html Last updated: 05.05.99; retrieved HERE )