The Earth has been changing throughout the 4.5 billion years. It experienced the formation of atmosphere, encountered meteor showers, volcanic breaks, and earthquakes. Furthermore, it witnessed the emergence and extinction of lives. According to the plate tectonics theory, the lithosphere of the earth is moving due to its lower density and the mantle’s convection. Since the theory of continental drift has been accepted in the 1960s, it has been a debate whether the plates movement is driven by activities in the mantle, or the plates themselves are self-driven. This essay will walk through the history of the continental drift theory, backed up by several key evidence proposed by Alfred Wegener and other geologists, and most importantly, the
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Like what is pointed out by Keith Runcorn in 1980, “In science a phenomenon or a hypothesis can become so familiar and its utility in providing as explanation, or consistent description of a greater number of diverse facts so evident, that the underlying mechanism may often be left unstudied (http://www.umich.edu/).” Thus in order to fully understand why the continental drift theory is widely accepted today, discovering the driving forces for the plates movement is significant. Before we go into the internal force inside of the Earth which drives the plates’ movement, it is necessary to first look at the Earth’s lithosphere. The tectonic plates are made of the Earth’s crust and the upper part of the mantle, and these two parts together are called lithosphere. From Figure 1, we can see that the plates fit together like a jigsaw puzzle. Although the plates are made of rigid rocks, the inner part of the Earth is even denser due to the higher pressure as we go deeper into the Earth, and this is why the plates “float”. The heat deep inside the Earth is moving through conduction as well as convection, and towards the surface of the earth. This is believed to be a main reason for the plates’ movement. “Scientists once thought that Earth’s plates just surfed on top of the mantle’s giant convection cells, but now scientists believe that plates help themselves move instead …show more content…
However, the heat energy was much greater in the early stages of the Earth because the heat is constantly created and lost from the interior of the earth. The major role in heat transfer is convection--a result of movement of material in the medium due to buoyancy. This accounts for 85 percent of the heat lost. As a result, the heat in the lower mantle is transferred to the cooler upper regions. Before the 1990s, it is believed by majority that “the only adequate mechanism for continental drift which have yet been suggested are based on the activity of convection currents in the Earth’s mantle, and the heat carried upwards by the mantle are originated by radioactive decay within the mantle and the core, supplemented by heat produced through the loss of gravitational energy due to a growing core (Bott, 1964).” There is a circulation of convection currents inside the mantle, and the rate at which heat is lost, according to heat budget of the earth, should equal the heat generated. However, at some area of the mantle, convection does not take place, so the temperature will rise steadily. Take the example given in the journal from Nature, “assuming heat production within the mantle at a rate about 0.036 u cal/g/yr. Based on chondritic model and a specific heat of 0.3 cal/g the temperature will rise
Like what is pointed out by Keith Runcorn in 1980, “In science a phenomenon or a hypothesis can become so familiar and its utility in providing as explanation, or consistent description of a greater number of diverse facts so evident, that the underlying mechanism may often be left unstudied (http://www.umich.edu/).” Thus in order to fully understand why the continental drift theory is widely accepted today, discovering the driving forces for the plates movement is significant. Before we go into the internal force inside of the Earth which drives the plates’ movement, it is necessary to first look at the Earth’s lithosphere. The tectonic plates are made of the Earth’s crust and the upper part of the mantle, and these two parts together are called lithosphere. From Figure 1, we can see that the plates fit together like a jigsaw puzzle. Although the plates are made of rigid rocks, the inner part of the Earth is even denser due to the higher pressure as we go deeper into the Earth, and this is why the plates “float”. The heat deep inside the Earth is moving through conduction as well as convection, and towards the surface of the earth. This is believed to be a main reason for the plates’ movement. “Scientists once thought that Earth’s plates just surfed on top of the mantle’s giant convection cells, but now scientists believe that plates help themselves move instead …show more content…
However, the heat energy was much greater in the early stages of the Earth because the heat is constantly created and lost from the interior of the earth. The major role in heat transfer is convection--a result of movement of material in the medium due to buoyancy. This accounts for 85 percent of the heat lost. As a result, the heat in the lower mantle is transferred to the cooler upper regions. Before the 1990s, it is believed by majority that “the only adequate mechanism for continental drift which have yet been suggested are based on the activity of convection currents in the Earth’s mantle, and the heat carried upwards by the mantle are originated by radioactive decay within the mantle and the core, supplemented by heat produced through the loss of gravitational energy due to a growing core (Bott, 1964).” There is a circulation of convection currents inside the mantle, and the rate at which heat is lost, according to heat budget of the earth, should equal the heat generated. However, at some area of the mantle, convection does not take place, so the temperature will rise steadily. Take the example given in the journal from Nature, “assuming heat production within the mantle at a rate about 0.036 u cal/g/yr. Based on chondritic model and a specific heat of 0.3 cal/g the temperature will rise