What Is at the Center of the Earth?
By studying earthquakes, scientists have discovered that the inside of the earth is divided into three main parts. First comes a crust of ordinary rock. This is twenty or thirty miles (48 km.) thick in most places. Next comes a layer of heavier rock that extends halfway to the center of the earth. This is known as the mantle.
Inside the mantle is the core. The core is made up of two layers. The outer core appears to be a sort of liquid metal. The ball-like inner core is actually the center of the earth. It is probably made up mostly of solid iron. Because the Earth has a ball of metal in the middle of it, the entire planet is magnetic.
Scientists believe the liquid outer core is what controls the Earth’s magnetic field. The magnetic field acts almost like a bubble. It protects the planet from charged particles floating around in the solar system, such as those from the sun. The magnetic North and South Poles are opposing sides of Earth’s big magnet.
The hard, metallic material in the core is balled up in the center of the Earth because it’s the heaviest material on the planet. When Earth was formed about 4.5 billion years ago, all the heavier substances sank toward the middle. The lighter and less dense material, such as air and water, stayed closer to the crust.
Inside the core, the metals are constantly moving. The core of the Earth rotates regularly. Some scientists say the inner core actually rotates faster than the rest of the planet! As the liquid outer core moves, it can change the location of the magnetic North and South Poles.