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Continental drift

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Continental drift.jpg

The continental drift is an ancient forerunner to the theory of plate tectonics, which suggests that continents have migrated to their present location following the breakup of a single landmass known as Pangaea (meaning "all lands" in Greek). The diagrams at right illustrates the break-up of this supercontinent, the existence of which figured prominently in the theory of continental drift. According to this theory, the supercontinent Pangaea began to break up about 225-200 million years ago.[1]

Contents

Evidence

The locations of certain fossil plants and animals on present-day, widely separated continents form definite patterns (shown by the bands of colors), if the continents are rejoined.

The continental drift theory was developed originally due to the similarity in shape of the South American and African shorelines, which causes them to appear as though they were once joined together. The occurrences of unusual geologic structures and of plant and animal fossils on these matching coastlines offered further substantiation, as the coastlines are widely separated by the Atlantic Ocean. It was reasoned that it was physically impossible for most of these similar organisms to have swum or have been transported across the vast oceans. Lastly, the presence of identical fossil species along the coastal parts of Africa and South America was the most compelling evidence that the two continents were once joined.[1]

The drifting of continents after the break-up of Pangaea explained not only the matching fossil occurrences but also the evidence of dramatic climate changes on some continents. For example, the discovery of fossils of tropical plants (in the form of coal deposits) in Antarctica led to the conclusion that this frozen land previously must have been situated closer to the equator, in a more temperate climate where lush, swampy vegetation could grow. Other mismatches of geology and climate included distinctive fossil ferns (Glossopteris) discovered in now-polar regions, and the occurrence of glacial deposits in present-day arid Africa, such as the Vaal River valley of South Africa.[1]

History

The belief that continents have not always been fixed in their present positions was first suggested as early as 1596 by the Dutch map maker Abraham Ortelius in his work Thesaurus Geographicus. Ortelius suggested that the Americas were "torn away from Europe and Africa... by earthquakes and floods" and went on to say: "The vestiges of the rupture reveal themselves, if someone brings forward a map of the world and considers carefully the coasts of the three continents." .[1]

In 1858, geographer Antonio Snider-Pellegrini made these two maps showing his version of how the American and African continents may once have fit together, then later separated.

A creation scientist by the name of Antonio Snider-Pellegrini later published the concept in his book, La Création et ses mystères dévoilés (Creation and its Mysteries Unveiled), in 1858.[2] To form his theory, Snider drew from Genesis 1:9-10 where it is explained that God gathered the seas into one place, suggesting the possibility of one single landmass at that point in time. He also observed the close fit of the Eastern South American coast and the Western African coast. He concluded that the Flood of Noah had caused subsequent horizontal movement of the supercontinent causing it to break, thus forming the tectonic plates. Snider's idea was overlooked, possibly due to the fact that Darwin's book had been published in the same year. Snider wrote a book and even had it translated into French, but still, his theory went unnoticed until the early twentieth century. At that time, the German meteorologist Alfred Wegener wrote a book on the idea of one original supercontinent called Pangaea.

But still, for about 50 years this thought was neglected due to a small group of seismologists who professed that the strength of the mantle rock was too great to allow continents to drift in the way Wegener had calculated. They estimated the rocks strength by watching the behavior of seismic waves as they went through the earth. But they were calculating the strength of the rocks at the time of their testing, not from back when the earth was in it's pre-flood state. During those 50 years, scientists who believed in the theory of one original supercontinent were considered ignorant people who didn't look at the facts. But today, that view has reversed.

Today, most scientists believe in the fact that the earth was once a supercontinent. Now we have more information on our planet due to mapping the ocean floor using sound waves, measuring the magnetic field above the seafloor, timing geomagnetic reversals of the past by unlocking the magnetic memory of the continental rocks, and locating earthquakes with a world-wide network of seismometers. [3]

However, it was not until 1912 that the idea of moving continents was seriously considered as a full-blown scientific theory -- called Continental Drift -- introduced in two articles published by a 32-year-old German meteorologist named Alfred Lothar Wegener. He contended that, around 200 million years ago, the supercontinent Pangaea began to split apart. Alexander Du Toit, Professor of Geology at Johannesburg University and one of Wegener's staunchest supporters, proposed that Pangaea first broke into two large continental landmasses, Laurasia in the northern hemisphere and Gondwanaland in the southern hemisphere. Laurasia and Gondwanaland then continued to break apart into the various smaller continents that exist today[1]

Plate Tectonics

World map of plate tectonic activity.
Main Article: Plate tectonics

Plate Tectonics is a widely-accepted model used to explain the configuration of the Earth's surface. The concept has revolutionized thinking in the Earth sciences in the last 10 years and combines many of the ideas about continental drift.[4]

The Earth's outermost rocky layer, the crust, exists as a number of puzzle-piece-like plates. We now know that there are seven major crustal plates, subdivided into a number of smaller plates. They are about 80 kilometers thick, all in constant motion relative to one another, at rates varying from 10 to 130 millimeters per year. Most of the geological action - mountains, rift valleys, volcanoes, earthquakes, faulting - is due to different types of interaction at plate boundaries.[4]

In particular, four major scientific developments spurred the formulation of the plate-tectonics theory:

  1. Demonstration of the ruggedness and youth of the ocean floor
  2. Confirmation of repeated reversals of the Earth magnetic field in the geologic past
  3. Emergence of the seafloor-spreading hypothesis and associated recycling of oceanic crust
  4. Precise documentation that the world's earthquake and volcanic activity is concentrated along oceanic trenches and submarine mountain ranges.[5]

Catastrophic plate tectonics

Main Article: Catastrophic plate tectonics

Catastrophic plate tectonics is a theory that proposes rapid movement of the Earth's plates during the flood of Noah. It was originally derived by Dr. John Baumgardner, and substantiated by sophisticated computer modeling.

Many creation geologists feel it fits with standard geology better than other flood models because it offers a scientific description of the flood of Noah that is compatible with plate tectonics and continental drift theories. It also provides a mechanism for the source and recession of the flood water (i.e. the fountains of the great deep), and accepts the conventional interpretation of events like earthquakes and volcanic activity. Because it simply requires an accelerated timescale for plate movement, the conflict with traditional uniformitarian geology is also minimal.

Problems

However, there are problems with the way this theory is typically portrayed to the public. For example, there is no solid evidence that the plates are still moving.[6] Also, radiometric dating of ocean bottom sediments has uncovered a major discepancy between the same Mid-Atlantic Ridge that runs between the Americas and Europe and Africa. For example, the North American and European half appears to have been taken 10 times as long to separate than the South American and African Plates. Also, it appears that global positioning systems have not confirmed that the plates are still moving apart in the manner that we thought.[7]

References

  1. 1.0 1.1 1.2 1.3 1.4 The Dynamic Earth: The Story of Plate Tectonics Chapter 1: Historical Perspective. by Jacquelyne Kious and Robert Tilling. U.S. Geologic Survey
  2. Antonio Snider-Pellegrini by Wikipedia
  3. Can Catastrophic Plate Tectonics Explain Flood Geology?by Andrew A. Snelling November 8, 2007
  4. 4.0 4.1 Earthquakes and Plate Tectonics by the U.S. Geological Survey, Earthquake Hazards Program.
  5. The Dynamic Earth: The Story of Plate Tectonics Chapter 2: Developing the Theory. by Jacquelyne Kious and Robert Tilling. U.S. Geologic Survey
  6. The Theory of Continental Drift by Randy S. Berg
  7. Is the Mid-Atlantic Ridge Still Spreading? by Randy S. Berg

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