Forty-eight years ago, Dan McKenzie graced us with his first paper on the “viscosity of the lower mantle”, or better known as the theory of plate tectonics. This theory states that the Earth is broken up in to plates that move in all different directions and speeds. The movement is caused by convection in the asthenosphere. The lower and hotter magma rises to the top and pushes the plates outwards, then cools and sinks. Also, in places like the Mid-Ocean Ridge, there are breaks in the Earth’s crust where magma comes up and replaces old rocks pushing them to either side. (Richardson) This theory is supported by irrefutable facts. Some of which are: the shapes of many of the continents look as though they at one time were all connected, there are similar fossils on almost all of the continents, and the oldest parts of oceanic plates are only around 200 million years old. This theory is as close to fact as it gets. When our Earth’s tectonic plates are viewed separately they look like nothing spectacular, but when viewed together in a different arrangement, it is almost impossible not to see how they fit together. It is believed that the continents were once all connected until 260 million years ago when some giant natural occurrence split them apart. (The Geological Society) This is a separate hypothesis that is known as Pangea which means all land. Scientists have worked tirelessly to assemble one giant land mass where continents stay in their current general area and fit together. With erosion as an opposing force, it is impossible to have an exact picture of what it was like, but what we currently have, comes extremely close. There are even fossils on the borders of plates that match with fossils on the borders of other plates. T... ... middle of paper ... ...ause the sea floor is expanding. He proves it by saying that the continents look like they were all connected at some point, that there are similar fossils on different continents that are now separated by hundreds of miles, and that the oceanic crust is made of different rocks that are all different ages. Dan McKenzie was an underpaid, underappreciated geophysicist that happened to write a phenomenal paper in 1966, now he is considered the man who solved one of the Earth’s greatest mysteries, the man that discovered plate tectonics. Works Cited Richardson, Eliza. "Dan McKenzie." Penn State. Penn State, 2014. Web. 19 Feb. 2014 "Dan McKenzie." Plate Techtonics. The Geological Society, n.d. Web. 19 Feb. 2014. "Continental Drift." Continental Drift. Enchanted Learning. Web. 19 Feb 2014. .
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)
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...
The Franciscan Terrane of central California represents an accretionary complex formed by long-term subduction of an oceanic plate under the Western margin of the North American craton. The Franciscan complex is composed of three distinguishable belts: the eastern belt (Yolla Bolly and Pickett Peak terranes), the central belt, and the coastal belt. Age and metamorphic grade of the belts decreases to the west (Blake and Jones, 1981). Formation of the accretionary complex began during the late Jurassic in the eastern belt and has continued into the Miocene along the western coastal belt. The complex trends NNW and is bounded by the San Andreas Fault to the east and by the coastal range fault to the west. The coast range fault separates the Franciscan complex with the partly coeval Great Valley sequence. Debate exists over the tectonic evolution of the Franciscan, centered around the geographic origin of the Franciscan rock units.
Ultimately the development of previous inferences and observations which have developed our current model for the Earth’s composition and interior structure are a key concept in understanding our future developments towards resourcing our planet and understanding how it works to a further degree.
Source 4. A map of the Earth’s fault lines and plates with the direction of their movement.
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.”
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
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.
Volcanism is a major part of the Galapagos and their formation. The island chain is positioned on the Nazca Plate, which is subducting beneath the South American Plate at a geologically rapid pace of 2.5 inches per year. In addition, this Nazca Plate is located directly on top of the Galapagos Hotspot. It is here that mantle plumes melt Earth’s crust, creating volcanoes as a product. The oldest island was first shaped by this ...
regions of the earth can indicate which rock layer is older than the other. Trilobite fossils
The Permian Period was the last period of the Paleozoic Era. During this geological time period’s earlier stages glaciation was extensive. Middle Permian began to warm, and by the late Permian the environment was hot and dry. The environmental conditions were so extreme that the marine and terrestrial life forms were greatly affected. According to research the drastic climate change could have been caused by the formation of Pangaea. In 1912 Alfred Wegener while studying his theory of the continental drift, discovered Pangaea’s very existence. A combination of all of Earth’s landmasses joined together and covered 1/3 of Earth’s surface. Pangaea was f...
First you might need to know definition of tectonics. It is a theory in geology. The lithosphere of the Earth is divided into a small number of plates which float on and travel independently over the mantle and much of the Earth’s seismic activity occurs at the boundaries of these plates. That is the official definition of Plate tectonics. secondly, this plate covers many parts of continents. plate boundaries don’t go according to Continents boundaries, they make their own boundaries. The North American plat...
Earth was formed 4.8 billion years ago (3) . It became the home for hazelnuts because it had an atmosphere and environment which allowed for life to prosper in later years. Earth’s surface was once composed of a single landmass, known as Pangaea (1).Over time it was broken up into seven different plates which were free to move as a result of movements in the hot, semi-liquid magma beneath the...