Pressures here are immense: well over 3 million times greater than on Earth’s surface. That’s almost as hot as the surface of the sun. It’s also intensely hot: Temperatures sizzle at 5,400° Celsius (9,800° Fahrenheit). The inner core spins a bit faster than the rest of the planet. Extremely dense, it’s made mostly of iron and nickel. It’s located some 6,400 to 5,180 kilometers (4,000 to 3,220 miles) beneath Earth’s surface. This solid metal ball has a radius of 1,220 kilometers (758 miles), or about three-quarters that of the moon. A cut-away of Earth’s layers reveals how thin the crust is when compared to the lower layers. Here’s a primer on Earth’s layers, starting with a journey to the center of the planet. Scientists - including Isaac Newton, three centuries ago - have also learned about the core and mantle from calculations of Earth’s total density, gravitational pull and magnetic field. The speed and behavior of these waves change as they encounter layers of different densities. They’ve plumbed it by studying how earthquake waves travel through the planet. Still, scientists know a great deal about Earth’s inner structure. In fact, the deepest humans have ever drilled is just over 12 kilometers (7.6 miles). Except for the crust, no one has ever explored these layers in person. They are, from deepest to shallowest, the inner core, the outer core, the mantle and the crust. Starting at the center, Earth is composed of four distinct layers. To really understand Earth, you need to travel 6,400 kilometers (3,977 miles) beneath our feet. Yet even the deepest canyon is but a tiny scratch on the planet. Earth’s surface is an amazing place to behold.
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