Respuesta :
Mountain ranges tower to the sky. Oceans plummet to impossible depths. Earth’s surface is an amazing place to behold. Yet even the deepest canyon is but a tiny scratch on the planet. To really understand Earth, you need to travel 6,400 kilometers (3,977 miles) beneath our feet.
This solid metal ball has a radius of 1,220 kilometers (758 miles) or about three-quarters that of the moon. It’s located some 6,400 to 5,180 kilometers (4,000 to 3,220 miles) beneath Earth’s surface. Extremely dense, it’s made mostly of iron and nickel. The inner core spins a bit faster than the rest of the planet. It’s also intensely hot: Temperatures sizzle at 5,400° Celsius (9,800° Fahrenheit). That’s almost as hot as the surface of the sun. Pressures here are immense: well over 3 million times greater than on Earth’s surface. Some research suggests there may also be an inner, inner core. It would likely consist almost entirely of iron.
This part of the core is also made from iron and nickel, just in liquid form. It sits some 5,180 to 2,880 kilometers (3,220 to 1,790 miles) below the surface. Heated largely by the radioactive decay of the elements uranium and thorium, this liquid churns in huge, turbulent currents. That motion generates electrical currents. They, in turn, generate Earth’s magnetic field. For reasons somehow related to the outer core, Earth’s magnetic field reverses about every 200,000 to 300,000 years. Scientists are still working to understand how that hap
At close to 3,000 kilometers (1,865 miles) thick, this is Earth’s thickest layer. It starts a mere 30 kilometers (18.6 miles) beneath the surface. Made mostly of iron, magnesium, and silicon, it is dense, hot, and semi-solid (think caramel candy). Like the layer below it, this one also circulates. It just does so far more slowly.
Earth’s crust is like the shell of a hard-boiled egg. It is extremely thin, cold, and brittle compared to what lies below it. The crust is made of relatively light elements, especially silica, aluminum, and oxygen. It’s also highly variable in its thickness. Under the oceans (and the Hawaiian Islands), it may be as little as 5 kilometers (3.1 miles) thick. Beneath the continents, the crust maybe 30 to 70 kilometers (18.6 to 43.5 miles) thick.
