The Shifting of Pangea
Have you ever noticed that a map of the world looks like a puzzle and the continents look like the pieces that would fit together to complete the puzzle.
In 1912, Alfred Wegener, a German scientist and an adventurer, came up with a theory that the continents had once been part of a “supercontinent”. Wegener proposed that, over 200 million years, what he called Pangea had separated and became individual pieces. Pangea means “all lands” in Greek, and that is what Pangea was, a very large landmass when all of the continents were connected. When Wegener first proposed this idea in 1912, people did not buy into this theory. One of the problems that Wegener faced was that he believed that the continents had drifted apart, but he couldn’t explain how they had drifted apart. Another problem was that there was a theory already in place called the “Contraction Theory”. This theory stated that the Earth was once a molten ball and in the process of cooling, the surface cracked and folded up on itself. One of the problems with this theory was that it suggests that all mountain ranges were the same age, and this could not be true. Wegner’s explanation was that continents shifted and these shifting plates would collide, encounter resistance from one another, compress, then fold upwards to form mountains near the edges of the plates.
Eons ago India and an ancient ocean called the Tethys Ocean sat on a tectonic plate. This place was shifting northward towards Asia at a rate of 10 centimeters per year. The ocean got progressively smaller unit about 55 million years ago when it collided with Asia. There was no more ocean left of lubricate the subduction and so the plates formed the High Plateau of Tibet and the Himalayan Mountains.
Evidence that Pangea may have existed can be found in land animals, vegetation, mountains, and the climate. Fossils and plants that are the same, can be found on different continents, across oceans. Assuming that the land was once connected, animals could have walked across the large land mass and not have to swim. For example, the mesosauras (a land animal) could not have traveled from South America to Africa because of the Atlantic Ocean. Yet, there are fossils of this animal on both continents. Another example is there are trees in South America, Africa, India, Australia, and Antarctica that are of the same origin.
The area composed of the Gander, Nashoba, Avalon, and Meguma Terranes has been extensively studied for many years. However, it was only recently that the terranes were recognized as distinct geologic entities with unique tectonic histories thus there is still much debate regarding the tectonic model which brought these terranes together (Hon et al., 2007). This paper will address the geology of the peri-Gondwanan terranes and propose a potential tectonic model for the accretional orogenic events. It will also primarily focus on the juxtaposition between the Nashoba and Avalon Terranes.
15. The pictures above show how the continents on Earth’s surface have changed position over a very long period of time. What explains this change? (S6E5e, f)
Later after the sea finally retreated occurred volcanic activity. Mountains rose through laccoliths, which also resemble volcanoes. These laccoliths differ in that they do not erupt. They shifted layers of rock upward in the shape of a dome. This specific piece of geologic morphology occurred at the end of the Cretaceous time. This marked the beginning of the Laramide Orogeny, which was a well-known period of mountain formation in western North America.
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.”
Periods that the folding occurred in which formed the outlines of the basin as it
After the Laramide orogeny things were still happening, just as always with Earth. Something is always changing even if it is not detectable day by day. Due to the Farallon Plate subducting there was a suction like effect going on because of the water that was being taken in with it (Humphreys). This would cause the North American plate to become weak and unstable, because it was being hydrated. This eventually would result in large plateaus and large amounts of uplift (Humphreys). There are many things that have been going on through out this time period but it all turns around and creates and shapes the earth into what it is today as well as what it will be in the future.
For example when he writes about how the axes of each continent affects how well ideas and domesticated crops and animals flow or spread through the continent. This discussion had made lots of sense for me and is yet another idea that supports his theory. "At the one extreme was its rapid spread along east-west axes: from Southwest Asia both west to Europe and Egypt and east to the Indus Valley (at an average rate of about 0.7 miles per year); At the opposite extreme was its slow spread along north-south axes: at less than 0.5 miles per year, from Mexico northward to the U.S. Southwest; at less than 0.3 miles per year, " This example shows how east to west axes allow for a faster diffusion of crops and animals. But the north to south is very slow compared to the other. This helps explain why Eurasia had developed the quickest and the America and Africa lagged behind." For example, Portugal, northern Iran, and Japan, all located at about the same latitude but lying successively 4,000 miles east or west of each other, are more similar to each other in climate than each is to a location lying even a mere 1,000 miles due south." This line tells us why Eurasia was able to develop so fast. That is because it has an east to west axes which means animals and crops can more wildly thought the same land due to there being large amounts of land with the same latitude. While the Americas
The theory concluded that around 200 million years ago, the heavy Pacific Plate collided with the lighter North American Plate, and started sliding underneath, a process known as subduction. This continued for 100 million years, until some 20 million years ago, when the Pacific Plate was forced to change direction and started sliding north, creating the San Andreas Fault. Most of California’s population sits on the west side of the fault, the Pacific plate, while the rest of North America is sitting on the east side of the fault, the North American
In 1912, Alfred Wegener, a German scientist, was the first to notice this and develop the theory of plate tectonics. He noticed that the earth’s continents fit together almost like a jigsaw puzzle. This, combined with the fact that similar fossils and rock types are found on different continents separated by large bodies of water, helped him formulate his conjecture. He contended that the plates at one point formed one large continent called Pangea, which allowed like fossils and rock types to become closer together, which broke apart. Despite how well the continents fit together and the facts about the geology, the general public would not accept Wagener’s proposal. This is largely due to religious conflicts and the lack of evidence presented to them.
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.
About 20 million years ago the last part of the Farallon sea floor plate subducted under the North American plate. This put the North American plate and the Pacific plate into contact, but unlike the Farallon sea floor plate, the Pacific plate sheared against the side of the North American plate. Because there was no plate subducting, the North American plate was in direct contact with the mantle (Tierney, 29). Heat from the mantle made the continental crust more ductile, which allowed the crust to extend and thin.
Ever since the beginning on time, Humans believed the ground is solid and immobile. But this is not true whatsoever. The Earth is every-changing and continually in motion. The stability of the Earth is not at all what we think it is. Thinking about the rotational axis of the Earth, and possibly of what the Earth may become at a certain point in time, has a great influence on understanding all aspects of living things, either in the past, present, or future. The Theory of Plate tectonics is accredited to most of the creations of Mountain Ranges, the Centennial drifting Theory, for earthquakes, and volcanic activity. Plate tectonics and mountains also play a big part in the Earth and its geological features.
The Mid- Atlantic Oceanic Ridge is the best known divergent boundaries. Divergent boundaries are when two plates move apart from one another. The Mid-Atlantic Oceanic Ridge is spreading at an average of 2.5 centimeters a year ("Understanding plate motions [This Dynamic Earth, USGS]", 2014). This underwater mountain range a prime example of seafloor spreading as well. Seafloor spreading creates new oceanic lithosphere when the two plates pull apart and magma is allowed to well up and fill the crack. This also causes underwater mountains to form if the magma flows upwards past the crust (Tarbuck & Lutgens, 2015). It is important to understand how these ranges are created, especially because they can give scientists an idea on when new islands or continents may be formed. It also allows scientists to understand what may cause other plates to diverge from one
Plate tectonics is a theory in earth science about plates that ride on the asthenosphere. These plate tectonics carry continents and ocean basins. There are seven major plate tectonic plates and many minor plates. There are two types of tectonic plates: oceanic and continental plates; continental plates have a density of 2.7 g/cm^3 but oceanic plates have a density of 3 g/cm^3.The area at which these plates meet are called plate boundaries. There are three types of plates boundaries that we have identified: convergent plate boundary, divergent plate boundary, and transform plate boundary.