Drifting Continents

Perhaps you once looked at a World map and right away noticed that South America and Africa looked like two pieces of a very large puzzle.  I don’t remember the exact day, but I was probably in elementary school in the 1960s.  All I do remember, is staring at a pull down map at the front of the classroom when I noticed the appearance of the puzzle pieces.

In all probablility, many other people noticed how the Earth’s land looks like puzzle pieces that have been scattered.  One scientist, Alfred Wegener, not only noticed this Drift-WegenersBookappearance, but developed an hypothesis and wrote about it. His thinking appeared in his book The Origin of the Continents and Oceans, published in 1915.

Dr. Wegener proposed that all of today’s continents split apart from a one time supercontinent he called “Urkontinent”.  In modern times, Urkontinent was renamed “Pangaea”.  But how might he prove his ideas? His hypothesis ran counter to accepted ideas in geology, geophysics, paleontology, and zoogeography. Even though Wegener’s discussion was presented very diplomatically, because his hypothesis crossed the various disciplines, it exposed him to the territoriality of old school thinking.

Wegener’s critics managed to keep Continental Drift discussion on the back burner of scientific discussion until the 1960s.   Meantime Wegener kept up his research efforts because he knew that arguments based only on the puzzle fit appearance could be explained as coincidental.  He delved into prior studies from the scientific fields that he had crossed.Drift-WegenerKontinente

From geology, he questioned why coal deposits, normally associated with tropical climate, are found near the North Pole. Why were fossils distributed in places one would not expect them to be, had there not been Continental Drift?.  Why did the plains of Africa exhibit strong evidence of glaciation?  The apparent match between the East coast of South America with the West Coast of Africa turned out to be an uncanny match up of geological features of the land and Continental shelves of each of the two Continents.  All of these questions suggested that the Atlantic Ocean did not exist before the Jurassic Age.

The biggest problem with Wegener’s findings was the lack of an explanation about how such a breakup of Pangaea occurred and how the various puzzle pieces moved into their present locations. After Wegener’s death, interest in Continental Drift stagnated until the mid 1950s.
Drift-Himalaya

British geophysicists Stanley Runcorn and Patrick Blackett had been studying Earth’s magnetic field and its history through the various ages.  They took note of the direction of change in planetary magnetization.  There was evidence of a “polar wandering curve”, that showed the magnetic poles had been located in other places during earlier times. Deeper research, though, showed the wandering curves are different for each Continent.  This observation caused the polar wandering curve hypothesis to be placed on hold. Later researchers looked into Wegener’s old writings and noted that a 30-degree westward drift of North America from Europe, since the Triassic Period, perfectly accounted for the magnetic curves.

Then, in the early 1960s, sonar and submarine technologies had undergone massive improvements.  More knowledge about the ocean floors from mapping and observation was coming to light.  Geophysicist Harry Hess presented an hypothesis stating that oceanic crust is continually generated by volcanic or igneous activity on the ridges of the ocean floor.  This activity causes horizontal movement of the seabed.

In the late 1960s, researchers Jack Oliver and Bryan Isacks integrated the ocean floor spreading and Wegener’s Continental Drift ideas into a new theory called “plate tectonics”. The theory states that the Earth’s surface consists of a few rigid “plates” that float atop of a partially molten layer of the Earth’s mantle.  As ridges of volcanic activity create new ocean floor material, these plates are forced apart and the Continents are forced to move away from the upwelling mantel material. Modern observations have shown that both the North and South American tectonic plates have been moving at around 2 centimeters per year.

Coupling the tectonic plate theory with studies about minerals and fossils seems to have affirmed the original findings of Dr. Wegener and his Continental Drift hypothesis.  It seems apparent that the breakup of Pangaea and the drifting of the puzzle pieces is the “latest” in a similar series of land movements throughout the history of our planet.

Ciao
1984a

The Blue Jay of Happiness hopes this very condensed version of tectonics will inspire you to conduct your own, more detailed, reading and investigation of this extremely interesting topic.

About swabby429

An eclectic guy who likes to observe the world around him and comment about those observations.
This entry was posted in Books, Controversy, Environment, History, Science and tagged , , , , , , , , , , . Bookmark the permalink.

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