- Earth's Heating Sources Article 2022

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Oct 30, 2023

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Earth’s Interior Heating Sources Why is the earth's core so hot? And how do scientists measure its temperature? Quentin Williams, associate professor of earth sciences at the University of California at Santa Cruz offers this explanation: There are three main sources of heat in the deep Earth: (1) heat from when the planet formed and accreted, which has not yet been lost; (2) frictional heating, caused by denser core material sinking to the center of the planet; and (3) heat from the decay of radioactive elements. Q: What are the 3 main sources of heat in the deep Earth? A. Heat from when the planet formed and accreted B. Frictional heating, cause by denser core material sinking to the center of the planet C. Heat form the decay of radioactive elements Q: Which of these three sources of heat is still providing (new) heat today? Why do you think so? Frictional heating and heat form the decay of radioactive elements It takes a rather long time for heat to move out of the Earth. This occurs through both convective transport of heat within the earth's liquid outer core and solid mantle and slower conductive transport of heat through non-convecting boundary layers, such as the earth's plates at the surface. As a result, much of the planet's primordial heat, from when the Earth first accreted and developed its core, has been retained. Q: List the two types of heat transport discussed above, then state where in the Earth that form of heat transport is important. A. Convection B. Conduction Q: What does the author mean by the statement that “the planet’s primordial heat … has been retained”? Inner core The amount of heat that can arise through simple accretionary processes, bringing small bodies together to form the proto-earth, is large: on the order of 10,000 kelvins (about 18,000° Fahrenheit). The crucial issue is how much of that energy was deposited into the growing Earth and how much was radiated back into space. Indeed, the currently accepted idea for how the moon was formed involves the impact or accretion of a Mars sized object with or by the proto-earth. When two objects of this size collide, large amounts of heat are generated, of which quite a lot is retained. This single episode could have largely melted the outermost several thousand kilometers of the planet.

Q: What does the term accretionary mean? Bring small bodies together to form the proto-earth Q: Would you describe the amount of heat “deposited” into the earth from accretionary processes as large or small? Explain why you think this based on the article. A lot of heat Additionally, descent of the dense iron-rich material that makes up the core of the planet to the center would produce heating on the order of 2,000 kelvins (about 3,000° F). The magnitude of the third main source of heat--radioactive heating--is uncertain. The precise abundances of radioactive elements (primarily potassium, uranium and thorium) are poorly known in the deep earth. Q: Frictional heating was a significant source of heat for the Earth when the earth was forming. How does the amount of heat provided by frictional heating compare to that of accretionary heating? It happen in the core Q: Radioactive heating is a significant source of heat today. How does the amount of heat provided by radiative heating compare to the other two? Explain your answer. idk In sum, there was no shortage of heat in the early Earth, and the planet's inability to cool off quickly results in the continued high temperatures of the Earth's interior. In effect, not only do the Earth's plates act as a blanket on the interior, but not even convective heat transport in the solid mantle provides a particularly efficient mechanism for heat loss. The planet does lose some heat through the processes that drive plate tectonics, especially at mid-ocean ridges. For comparison, smaller bodies such as Mars and the Moon show little evidence for recent tectonic activity or volcanism. Q: What sort of heat transport happens in Earth’s solid mantle? Convection Q: Where does heat loss from the Earth’s interior occur? Plate tectonic and mid ocean ridges We derive our primary estimate of the temperature of the deep Earth from the melting behavior of iron at ultrahigh pressures. We know that the Earth's core depths from 2,886 kilometers to the center at 6,371 kilometers (1,794 to 3,960 miles), is predominantly iron, with some contaminants. How ? The speed of sound through the core (as measured from the velocity at which seismic waves travel across it) and the density of the core are quite similar to those seen in iron at high pressures and temperatures, as measured in the laboratory. Iron is the only element that closely matches the seismic properties of the Earth's core and is also present in sufficient abundance in the universe to make up the approximately 35% of the mass of the planet present in the core.

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