2023-07-04 23:00:39
The slice you see cut into the ground reveals its core, shown here in bright yellow. Our Earth, built in layers similar to an onion, consists of a crust, mantle, outer core, and inner core, each with its own characteristics. How did the Earth’s core stay as hot as the Sun’s surface for billions of years? The stratified structure of the Earth, which includes moving plates, is heated by leftovers from planetary formation and the decay of radioisotopes. Geologists use seismic waves to study these internal structures and motions, which are essential to environmental changes and the evolution of life on Earth. Internal heat drives plate motions, contributing to phenomena such as earthquakes and volcanic eruptions and creating new lands and oceans, making the Earth habitable. The structure of our land is much like an onion – layer after layer. Starting from top to bottom is the crust, which includes the surface on which you walk; Then the mantle descends, consisting mainly of solid rock; then deeper, the outer core, made of liquid iron; And finally, the inner core, made of solid iron, whose radius corresponds to 70% of the volume of the Moon. The deeper you dive, the hotter it gets – parts of the core are as hot as the surface of the sun. This illustration shows the four subsurface sections. Journey to the Center of the Earth As a teacher of earth and planetary sciences, I study the interior regions of our world. Just as a doctor can use a technique called ultrasound to image the structures inside your body with ultrasound, scientists use a similar technique to image the internal structures of the Earth. But instead of ultrasound, geoscientists use seismic waves — sound waves generated by earthquakes. On Earth’s surface, you see dirt, sand, grass, and of course sidewalks. Seismic vibrations reveal what’s underneath: rocks big and small. It is all part of the earth’s crust that can go down to a distance of up to 30 kilometers; It floats above a layer called the mantle. The upper part of the mantle generally moves with the crust. Together they’re called the lithosphere, which is about 60 miles (100 kilometers) thick on average, although it can be much thicker in places. The lithosphere is divided into many large blocks called plates. For example, the Pacific Plate lies under the entire Pacific Ocean, and the North American Plate covers most of North America. The plates are somewhat like saw cuts that fit roughly together and cover the surface of the earth. the panels are not stationary; Instead, they move. Sometimes it’s the smallest fraction of an inch over a period of years. Other times, there is more movement, and it is more sudden. This type of movement is what causes earthquakes and volcanic eruptions. Furthermore, plate motion is an important, and perhaps necessary, factor in the evolution of life on Earth, because moving plates alter the environment and force life to adapt to new conditions. From seeing all life happen at your feet. The heat is on and the movement of the plate requires a warm coat. Indeed, the deeper you go into the ground, the higher the temperature. At the bottom of the plates, at a depth of about 100 kilometers, the temperature is about 2,400 degrees[{” attribute=””>Fahrenheit (1,300 degrees Celsius). By the time you get to the boundary between the mantle and the outer core, which is 1,800 miles (2,900 kilometers) down, the temperature is nearly 5,000 °F (2,700 °C). Then, at the boundary between outer and inner cores, the temperature doubles, to nearly 10,800 °F (over 6,000 °C). That’s the part that’s as hot as the surface of the Sun. At that temperature, virtually everything – metals, diamonds, human beings – vaporizes into gas. But because the core is at such high pressure deep within the planet, the iron it’s made up of remains liquid or solid. plate tectonics, humans probably wouldn’t exist. Collision in space Where does all this heat come from? It does not come from the sun. Although it warms us and all plants and animals on Earth’s surface, sunlight cannot penetrate miles into the planet. Rather, there are two sources. One is the heat inherited by the Earth when it formed 4.5 billion years ago. Earth is made from the solar nebula, a giant cloud of gas, amid endless collisions and mergers of chunks of rock and debris called planetesimals. This process took tens of millions of years. An enormous amount of heat was produced in these collisions, enough to melt the entire Earth. Although some of this heat was lost to space, the rest was trapped inside the Earth, where much of it remains today. The other source of heat: the decay of radioactive isotopes scattered everywhere on Earth. To understand this, first imagine an element as a family with isotopes as members. Each[{” attribute=””>atom of a given element has the same number of protons, but different isotope cousins have varying numbers of neutrons. Radioactive isotopes are not stable. They release a steady stream of energy that converts into heat. Potassium-40, thorium-232, uranium-235, and uranium-238 are four of the radioactive isotopes keeping Earth’s interior hot. Some of those names may sound familiar to you. Uranium-235, for example, is used as a fuel in nuclear power plants. Earth is in no danger of running out of these sources of heat: Although most of the original uranium-235 and potassium-40 are gone, there’s enough thorium-232 and uranium-238 to last for billions more years. Along with the hot core and mantle, these energy-releasing isotopes provide the heat to drive the motion of the plates. No heat, no plate movement, no life Even now, the moving plates keep changing the surface of the Earth, constantly making new lands and new oceans over millions and billions of years. The plates also affect the atmosphere over similarly lengthy time scales. But without the Earth’s internal heat, the plates would not have been moving. The Earth would have cooled down. Our world would likely have been uninhabitable. You wouldn’t be here. Think about that, the next time you feel the earth under your feet. Written by Shichun Huang, Associate Professor of Earth and Planetary Sciences, University of Tennessee. Adapted from an article originally published in The Conversation.
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