Continental Drift

Tectonics and Continental Drift Past and Present Locations

Abstract
When we look at our earth’s surface now it has seven continents, and five of them are divided by the oceans that surround them. In 1912 Alfred Wegner (1880-1930), came up with a theory called the continental drift; stating that over three hundred years ago all seven continents were once one super continent called Pangaea. Wegner tried to convince other scientists and geologist for many years that the continents drifted apart; however he didn’t have the geological mechanism that was needed to validate his theory. Throughout his search he did find a paleontological paper that signified that there was a land bridge connecting Africa and Brazil. The geographic evidence that prove that the continents drifted apart is; by the large ocean ridges that were formed by molten material that has risen from the earth, it is the molten material to be believed the reason for the continents drifting apart. The recognizable reason would be how the continents fit perfectly together like a puzzle, and the many fossils and rocks were found on the coastlines that would not have been able to exist in the areas they were found, pointing to the continents drifting apart. It wasn’t until 1950’ when scientist’s verified that there was paleomagnetic evidence that supported Wagner’s theory on the continental drift, and why the continents drifted apart; unfortunately Alfred Wegner had passed away in 1930 when he was on a dogsled excursion in Greenland, and he died knowing that his theory wasn’t believed by many people. (BookRags)

Tectonics and Continental Drift Past and Present Locations
Alfred Wagner an adept investigator, spent most of his life trying to convince geologists of his theory called the continental drift. He found some documentation that there was a land bridge that connected Brazil and Africa and he tried to explain the fossilized animals and plants that were found in Africa and South America; North America and Europe; India and Madagascar, all came from the same time period, and there would have been impossible for these creatures and plants to travel across the Oceans that we have now. Wagner also claims that there were Striae left by glaciers over land, proving that continental glaciation took place in the Pennsylvanian era. There is an indication that South Africa, and South America, were close together and South America, and Africa were also close together, during the ancient ice age. Wagner also explained his Contraction theory for the mountain formation, he was proposing that there was a molten ball and that when it cooled the surface it cracked and folded making the mountains form the way they did, and that as the continents drifted that the mountains that were formed due to resistance causing them to contract and move upward. Mountains on the Pacific coast of North America, The Sierra Nevada, and Andes on the coast of South America were cited. Wegener indicated that India coasted northward into the Asian continent that formed the Himalayas. (Weil, 1997)
Wegner claimed that the rotation of the earth caused a centrifugal dynamism in the direction of the equator; he claimed that Pangaea was originally close to the South Pole he proposed centrifugal dynamism causing the continents to break away and the subsequent continents to move in the direction of the equator. He named this "pole-fleeing force". Wegner also purposed that the Americas moving west was caused by gravity forces from the moon and sun (Weil, 1997) because Wegner was not able to validate his theories ended in scientific dismissal.
Arthur Holmes expounded in 1929, one of Wegner’s theories that mantle undergoes thermal convection which is when a substance is heated that substance concentration decreases, and rises to the top of the surface and then when it cools down it goes back down again if the process continues to be repeated thus causing the currents to be enough to be the reason for the continents to move. Although this idea had little notice; Holmes compared it to be similar to a conveyer belt because the emergence pressure was strong enough to break apart the continents thus forcing the broken continent to move in the opposite direction that was carried by convention currents. In 1948 after eighteen years after Alfred Wegner passed, there was a scientist exploring islands in the Atlantic Ocean, and found that the highest points of the mountain ranges were made of younger volcanic rocks, which is called the Mid-Atlantic Ridge. This was an important discovery was an important piece of evidence into the theory of why the continents drifted apart. Since they used submarines in World War II, they wanted to investigate the oceanic floor by ships, and they were able to create sonar maps of the ocean floor, by using a proton-precession magnometer, they found a steep valley at the center of the mid-ocean ridge, deep ocean trenches that were only in certain locations, as well they found that the Mid-Atlantic Ridge went around the entire earth passing through the ocean floors that the scientists compared it to the seams in a baseball. Scientists have always believed that the continental crust sat on top of the ocean crust, was just one piece; however evidence that there was cracks in the earth that is called lithosphere proving that both crusts were different parts made of the same piece of crust; that the scientists called plates, which is large pieces of lithosphere fitting together like a puzzle.
With all of the evidence found so far; enthusiastic and determined scientists were more determined than ever to find many unanswered questions regarding the continental drift; that’s why they decided to research the oceanic floor for more answers. The first clue that found was called magnetic reversals this is when magna cools making new lithosphere; there are natural iron oxides that are in the rock that act like magnets aligning with the magnetic field of the earth which meant that magnetic poles of the earth shifted, and there for the location of pole can be found by looking at the rock. When the scientist began measuring the ocean floor they found an identical pattern of stripes on each side of the mid-ocean ridges, confirming that they formed at the same time moving in opposite directions, which now brought them to the idea of seafloor spreading, this happens when magna leaks out of the cracks onto the ocean floor; thus pushing the current ocean crust to the side making it wider, and this was proof that lithosphere moved on the earths surface. Scientists also used earthquake data, by examining the patterns and locations; this is the last clue since they were able to match the locations of cracks which are known as faults in the lithosphere.
Throughout the years, and all of the data and new discoveries the plate tectonics is made up of a thin and rigid plates that are always in motion; each plate are made up of layers, and the surface is made of the continental crust, or oceanic crust or both, the bottom are made from the rigid upper layer of the earth’s mantle. These rigid plates slowly go down into soft plastic continental crust, and these plates all move at different rates. There are 3 types of plate boundaries; transform boundaries; are two plates that move laterally passing one another and oceanic crust is neither destroyed nor created. Divergent plate margins; is caused by a ridge or rise causing new oceanic crust to form in the gap between the plates therefore increasing the plate area as the plates move apart laterally away from the plate boundary, the ridge or rise is caused from a transform fault; This activity happens around central zone of the major ocean basins. Convergent plate boundaries; have two plates that move towards one another as one slide down the other at a forty-five degree angle into the earth’s mantle that happens amongst the seduction zone resulting from a deep earthquake, marking the surface as a deep ocean trench, when both plates hit each other it causes a volcanic island arc, as the plate is subducted under the other, it starts to melt around ninety to one hundred and fifty km, and then the magna begins to rise above the subduction zone forming a chain form volcanoes, and the edge of the plate that has not descended is marked by the chain of volcanic islands. The Himalayas, were formed when the plate that carries India crashed with the plate that carries Eurasia, and still very active and moving 3-4 inches each year. As a result to the instability of the many volcanos in the Pacific Ocean, and it is surrounded by a nearly continuous plate-collision zone, calling this the 'Ring of Fire '. (Bloes, Bohnenkamp, Bisbee & Garofolo, 2011) Plate tectonic provides mechanism: * Continents moving across the surface of the earth * Volcanos and patterns may change and shift directions across the earth as plates and their boundaries change and move * There is a chance that new oceans and sedimentary basins may develop * Sedimentary basins and oceans close and are distorted to create mountains With all of the accumulated evidence that the many scientists have been done throughout the years, they have come to the conclusion that continents didn’t move through the crust, but was just a big piece of the crust that is called plates; discovering that the continents was just a part of the whole plate. Together with the original theory of the '’Mystery of the Drifting Continents”, and all of the new evidence combined forming a new theory “plate tectonics”

References:
Bloes, K., Bohnenkamp, S., Bisbee, J., & Garofolo, A. (2011). Landforms. Retrieved from http://maps.unomaha.edu/peterson/funda/links/landforms/landforms.html
BookRags. (n.d.). Alfred Wegener introduces the concept of continental drift. Retrieved from http://www.bookrags.com/research/alfred-wegener-introduces-the-conce-scit-0612345/
Evidence for the mechanism of continental drift. (n.d.). Retrieved from for-the-mechanism-of-continental-drift.html
Weil, A. (1997, August 22). Ucmp berkeley. Retrieved from http://www.ucmp.berkeley.edu/geology/techist.html

References: Bloes, K., Bohnenkamp, S., Bisbee, J., & Garofolo, A. (2011). Landforms. Retrieved from http://maps.unomaha.edu/peterson/funda/links/landforms/landforms.html BookRags. (n.d.). Alfred Wegener introduces the concept of continental drift. Retrieved from http://www.bookrags.com/research/alfred-wegener-introduces-the-conce-scit-0612345/ Evidence for the mechanism of continental drift. (n.d.). Retrieved from for-the-mechanism-of-continental-drift.html Weil, A. (1997, August 22). Ucmp berkeley. Retrieved from http://www.ucmp.berkeley.edu/geology/techist.html