Everyone has pondered how hot the inside of the earth is, especially on a hot summer day. But just how hot is the earth’s mantle?
The earth’s mantle is sandwiched between the crust and the core, so temperatures change depending on the depth. The mantle closer to the crust can reach 1,652°F and when you get nearer to the core, temperatures can reach 7,230°F. For reference, the temperature of the surface of the sun is about 10,000°F. That’s a hot sandwich!
What is the mantle and what does it do?
The mantle is the second layer of the earth and is also the largest, running about 1,800 miles thick. It upholds the crust and is ultimately responsible for the qualities determining habitability. It consists of various materials like iron and magnesium-silicates, which all have different melting points and behaviors at certain temperatures. This helps to determine how hot the earth’s mantle is at different depths between the crust and the core.
The various materials composing the mantle and the temperature differential from the cooler crust and hotter core allow the mantle to behave as a very viscous liquid. Interestingly, the mantle is solid, dense rock, but the liquid-like state is important. This is what causes the tectonic plates that rest below the crust to move. These shifts in tectonic plates are responsible for such events like earthquakes, mountain formations, volcano eruptions, and continental drift.
How do we know how hot the mantle really is?
For many reasons, it’s impossible to take a temperature reading of the mantle on-site. Aside from the aforementioned extreme temperatures, the pressure as you move towards the center of the earth would be crushing. Fortunately, laboratory experiments can simulate the conditions of the mantle to get an approximation of the temperature scientists could expect.
Estimates are made by using the melting points of the known materials that compose the mantle along with the high pressures of the depths along this layer of the Earth. Once the role of water is factored in more information about the true temperatures of the mantle is understood. Water is a critical part of determining a better approximation of what the temperature of the mantle might be. This is because the more water there is in a rock, the lower the melting point. Scientists simulated a mantle-like sample under mantle-like conditions with the addition of olivine, a mineral naturally found in the mantle.
Olivine, like water, became an integral part of the synthetic mantle sample. After careful analysis, the synthetic substance was found to contain approximately the same amount of water as a true sample of the mantle. Scientists can use this information to conclude that the melting of the mantle occurs at a shallower depth than expected. With that, better estimations of where the mantle is melting and at what temperature are made.
The importance of a closer approximation of the mantle’s true temperature gives geologists a more clear picture of tectonic movements. Understanding these movements can paint a more clear picture of the origins of mountains, continental movement, and convection currents.
What causes the mantle to heat up?
The core of the earth is hot, so naturally it can be assumed that is the reason for the temperatures of the mantle. However, the responsibility for the heat in the mantle comes from the radioactive decay of isotopes, which accounts for almost half of the heat.
Over time, Earth will continuously lose heat to the surrounding universe. The radioactive decay of isotopes like potassium and uranium helps to keep the Earth from too much heat loss, which is good for it to stay a habitable planet!
Other contributions to the temperature of the mantle include the heat from the core of the earth, as suspected. Heat transfer from the cooling of the crust as centuries pass, known as secular cooling, is another factor.
The photo featured at the top of this post is © Rost9/Shutterstock.com
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