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Plate tectonics and continental drift essay
Introduction to continental drift and plate tectonics
Evidence of continental drift theory
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Today, when people want to cross over the ocean and get to another continent, they have to take plane for eight or more hours or ship for few days. However, if people were born millions of years ago, they might easily cross a boundary of tow continents by accident. Because according to the continental drift theory, ages ago, the continents today were a completed one piece and called Pangaea. (Sandner, 506-507) The continental drift theory is a theory first proposed by a German geologist and meteorologist Alfred Wegener in 1915. This theory suggests that parts of the Earth’s crust which are called continents were slowly drifting above a liquid core. He didn’t randomly come up with this idea with whim, there are actually some solid evidence to support this theory. For example, the boundaries of South America’s eastern coastline and Africa’s western coastline are seemingly matched on a world map. Also, you can find similar animals and plants fossils around different continent shores, like the fossil of Mesosaurus was found both in South Africa and Brazil. (Rejoined continents [This Dynamic Earth, USGS].) Not only fossil proves this theory, but also same living animals are found on two different continents. Furthermore, Wegener found out that same rocks and mountain ranges begin on one continent, and end at one coastline; but on another continent cross the ocean, there are similar rocks and mountain ranges appear. For instance, people found rocks with same types and rocks in Greenland, Ireland, Scotland, and Norway which are places really far away from each other. Last but not least, base on climatic evidence, scientists later pointed out that there are glacial striations in South America, Africa, Madagascar, Arabia, India, Anta... ... middle of paper ... ... at hot spots rather than plate boundaries. The Hawaiian Islands are an example of a chain of shield volcanoes. Compare to composite volcanoes, shield volcanoes’ magma is much thinner, therefore less gas will be trapped which leads to a less explosive eruption. Rift eruptions describe when magma erupts along cracks in the lithosphere. Rift eruptions are much less violent compare to other volcanic eruptions, but it releases a great amount of lava. Rift eruptions are common at ocean ridges like the Mid-Atlantic Ridge. (Sandner, 532-534) Maybe earthquakes and volcanic activities sound really scary to people, and always bring destructive damage to people, they are natural phenomenons that we should learn to understand and accept. It is impossible for people to completely avoid them all, but we can use our knowledge to predict them and reduce the damage to the least.
Mauna Loa is located on a hot spot in the Pacific Ocean. It is not near a plate boundary, in fact it is 3,200 km from the nearest plate boundary, and is situated in the middle of the Pacific tectonic plate. This is actually a rarity, as 90% of volcanoes are along a tectonic plate boundary. A hot spot occurs where long, stationary vertical pools of magma rise up and towards the plate. Movement of the tectonic plates above the hot spot created Mauna Loa, along with the other Hawaiian volcanoes. The older Hawaiian Islands were once above this stationary hot spot, but have been carried northwest by the slowly moving Pacific plate. As the plate moves, it carries the previously formed, older, volcanoes with it, creating a trail of younger, new volcanoes behind. The islands are lined up along the Hawaiian Ridge-Emperor Seamounts chain, which is 3,750 miles and includes Kauai, Maui, Oahu and Hawai’i, from north to south, respectively. There are around 80 volcanoes in this chain; most of them underwater, consequently the term seamount refer to submarine volcanoes. Three volcanoes of Hawai’i, Mauna Loa, Kilauea and Loihi seamount, are all currently sharing the Hawaiian hot spot. Although, recent evidence has shown that all three volcanoes use have separate plumbing systems to expel the lava from the pool of magma deep below them. It has also been suggested that Loihi is slowly moving Mauna Loa from the center of the island, thus shifting directly over the hot spot. The closer to the hot spot a volcano is, the more active it will be. The Hawaiian hot spot has laid down layers of lava, building up enormous islands from the ocean floor.
As Kohala Volcano emerged from the sea and joined with Mahukona, a much larger Big Island began forming. With continued movement of the Pacific Plate, the center of volcanism migrated on to Mauna Kea and Hualalai, the middle-aged volcanoes, and finally on to Mauna Loa and Kilauea, which are the youngest volcanoes on the island. Over the geologically short time of several hundred thousand years, these volcanoes erupted thousands of thin flows which spread over, and built upon, older flows; each volcano growing until it finally emerged from the sea. As time went on, lava flows from one volcano began to overlap flows from other, nearby volcanoes and eventually the peaks coalesced into a single island, the Big Island. In geologically recent times, a new volcano, Loihi, began forming about 18 miles off the southeast coast of the Big Island.
Earthquakes are a natural part of the Earth’s evolution. Scientific evidence leads many geologists to believe that all of the land on Earth was at one point in time connected. Because of plate tectonic movements or earthquakes, continental drift occurred separating the one massive piece of land in to the seven major continents today. Further evidence supports this theory, starting with the Mid-Atlantic ridge, a large mass of plate tectonics, which are increasing the size of the Atlantic Ocean while shrinking the Pacific. Some scientists believe that the major plate moveme...
To set the stage, we must go back 270 million years ago when a majority of the earth’s land masses were collected together in a single continent, a supercontinent, named Pangaea (Encyclopedia Britannica, 1). Historian Alfred Crosby explained that this collected all of earth’s land based biology into a single place, creating a single Darwinian “arena for competition” (Crosby, 1). Or in other words, one big evolutionary pot. Crosby also explains that 180 million years ago, Pangea split into two major land masses, what is now the Americas in the Western Hemisphere as one land mass and Euro-Asia and Africa as the second lass mass (Crosby, 1). What was once a single evolutionary pot, was now two, allowing for plant and animal life to take different evolutionary paths. These two worlds remained relatively separate from each other until the arrival of Christopher Columbus and other European explorers. That contact between the old world and the new world brought two distinct evolutionary arenas crashing into each other and returned a majority of the earth’s landmass into a single Darwinian pot, (Crosby, 1) This was Crosby’s re-knitting of the torn “seams of Pangaea.”
Evaluating the Evidence for Continental Drift There are several pieces of evidence certifying the existence of continental drift. They include mid oceanic ridges, fitting of continents, similarities of fossils on different continents and rock matches. The mid-oceanic ridges rise 3000 meters from the ocean floor and are more than 2000 kilometres wide surpassing the Himalayas in size. The mapping of the seafloor also revealed that these huge underwater mountain ranges have a deep trench, which bisects the length of the ridges, and in places is more than 2000 meters deep. Research into the heat flow from the ocean floor during the early 1960s revealed that the greatest heat flow was centred at the crests of these mid-oceanic ridges.
Basalt forms due to the partial melting of the layer of the mantle called the asthenosphere. The asthenosphere is the plastic zone of the mantle beneath the rigid lithosphere. Mantle plumes coming from the mesosphere can cause the asthenosphere to melt with heat or even if pressure decreases, which is called decompression melting (Richard 2011). The magma that forms from this melting is mafic magma that solidifies once it reaches the earth’s surface and cools quickly. The above process mainly occurs mainly during intraplate igneous activity which is the main explanation for volcanic activity that occurs a long distance away from a plate boundary. If the tectonic plate above the mantle plume is moving it can create a string of volcanic activity such as in Hawaii. See Fig 2.
Diop argued that the first civilizations emerged in the Nile Basin on the eastern coast of Africa. It is from this basin that African people fanned out across the continent and onto other lands around the 6th century BC. There exist two theories of human origin: monogenetic and polygenetic. The monogenetic view states that there is one source for mankind; man was born in one place and became different due to the climatic conditions to which he was exposed. The polygenetic opinion claims that man has several locations of origin, which would explain the physiological differences between the races. Followers of this theory believe that man was born in Africa, Europe, and Asia and there was no evolutionary or climatic development. Diop states that there are two reasons why this theory is faulty. He says that nature never strikes twice in its evolution; she doesn't create the same being twice. In addition, complete fossils have been found on the African continents, which proves that life began there. No such fossils have been found anywhere else in the world. In 1912, a British geologist attempted to prove that life had begun in England by piecing together a fake fossil supposedly found on British soil. The fabricated skull was later found to have been a fake by an English anthropologist in the 1950's. It was determined to have been constructed using the mandible and canine teeth of a monkey.
With regards to the multi-regional continuity model of human evolution, there is without a doubt a preponderance of fossil data that supports the diverse origins of Homo sapiens in different regions of the globe. Skulls displaying a wide variety of mixed modern and archaic features have been found in every corner of the world. The mere existence of these fossils is evidence enough to prove that human evolution was far less cut-and-dried a process than the advocates of the replacement model of human evolution would like to suggest, and, in fact, rather astonishingly complex.
...s from the Paleozoic, Mesozoic, and Cenozoic periods show proof of how animals have gone through evolution and why certain fossils look very similar. The Law of Original Horizontality and the Law of Superposition both express true when looking at modern rock layers today. The Law of Original Horizontality happens when sediments are constantly deposited over old layers of rock forming new layers over millions of years, while the Law of Superposition is the law that older rock layers lie beneath the newer layers. Also, Pangea and Panthalassa are now the seven continents and four oceans of the world today as a result of Continental Drift. All things considered, Rock layers are therefore evidence of Evolution for, rock layers holds proof of evolving animals seen through fossils, the plates in the earth separated Pangea, and the relation of evolution and rock layers.
Since the beginning of human kind there has been a cloud of wonder of how our planet was formed. Scientist interested in this field through out the years have developed many different theories to how our planet came about. Before the Twentieth Century, scientists and geologists thought that mountain structures were due to the massive tightening of the earth caused by the gradual cooling of molten rocks. In 1900, American scientist Joseph Le Conte, published an article in the Appleton's Popular Scientific Monthly. He described that the problem in understanding mountain building was establishing the cause of sideways pressure. It was not until 1910, that an American Geologist named F.B.Taylor, proposed the idea of a continental drift. Other scientists dismissed Taylor's idea, because there was just not enough proof. However, Taylor's idea was then backed up by a German scientist named Alfred Wegener. He proposed that the continents surrounding the Atlantic Ocean, Africa and South America fit together like a jigsaw puzzle. His broad range of studies enabled him to incorporate his theory of Plate Tectonics. Wegener, later in 1915 while in the German military published his idea that interpreted how his continental drift theory worked. He proposed that a huge landmass called Pangea, meaning ("all land") existed 200 million years ago. He furthered explained that this super continent began to drift apart very slowly throughout millions of years into what it looks like now. Wegener went on several expeditions through out his life to the continents of South America and Africa.
Alaskan volcanoes are different from Hawaii’s because they do not ooze out lava; they explode ash that can go up to 50,000 feet. If high enough, the ash can enter the Jet stream, a band of strong westerly air currents encircling
Volcanoes can cause damage by spewing lava, but earthquakes before the eruption can also cause damage. These earthquakes open fissures and let magma out to the surface. When the magma exits these fissures, streams of lava up to hundreds of feet can shoot into the air. The picture below shows the lava erupting from the fissures created by the earthquakes in...
...t of laurasia, just like most of the other plates. North America,Europe, and Green land all used to be connect because of Pangea ( as mentioned earlier). But when everything started to separate, first europe, then green land, and lastly the North American plate. After pangea was no more and the plates all started moving, the continents started going their own ways, there fore putting the continents where they are today.
Evidences has also point out discoveries found of humans living in other part of the continents by their paintings and engravings on stone from thousands of years early. Migrations from Africa early humans first expanded their range in eastern and southern Africa. They ventured out of Africa. This also points out that this new species displaced older human populations, such as the Neanderthals in Europe, and penetrated for the first time into the Americas, Australia, and the Arctic. People would have been able to cross a land bridge from northeastern Asia in to North America, perhaps beginning around 18,000 B.C.E. some scholar date it earlier or later (Bulliet, “et al” p.9).
Understanding the plate tectonics theory is very important, especially when investigating natural disasters like earthquakes, and volcanic eruptions. It is also gives scientists the ability to understand how mountains were formed between two tectonic plates. There are three types of interactions between plate boundaries: convergent, divergent and transform. Looking back at the history of these three different interactions, earthquakes, like the one in Haiti, volcanic eruptions, like at Mount St. Helens, and the creation of mountain belts, like the Mid-Atlantic Oceanic ridge, gives information on future consequences of tectonic movement, and what can happen when the plates interact with each other.