Earth & Its Anatomy

Mountain ranges touch the sky and oceans plummet to impossible depths. Earth’s surface is an interesting place. Earth is made up of four layers. Beginning at the center - inner core, outer core, the mantle, and the crust. The deepest any human has traveled is just 12 kilometers, which took 20 years.

The Inner Core

The inner core is a solid ball with a radius of 1220km, located 6400km - 5180km under the Earth’s surface. It is extremely dense and is made up of mainly iron and nickel. It is also extremely hot with temperatures reaching 5400 Celsius, making it as hot as the surface of the sun. The inner core is also under great pressure almost over 3 million times greater than on Earth’s surface.

The Outer Core

The outer core is also made up of mainly iron and nickel but just in liquid form. It is 5,180 to 2,880 kilometers below the surface. It is heated due to the radioactive decay of the element’s uranium and thorium, this liquid churns in huge, turbulent currents. This generates electric currents which also generate Earth’s magnetic field. The Earth’s magnetic field gets reversed after every 200,000 to 300,000 years. Scientists are still trying to understand it.

The Mantle

The mantle is the Earth’s thickest layer at 3000km thick, starting at just 30km under the Earth’s surface. It consists of mostly iron, magnesium, and silicon, it is dense, hot, and semi-solid form. Just like the outer core, the mantle also circulates but much slower.

The mantle’s temperature is also the melting point of rock. It forms a layer of partially melted rock sludge called the asthenosphere (As-THEEN-oh-sfeer). Geologists have come to believe this slippery part of the mantle is what Earth’s tectonic plates ride upon and slide across. Diamonds are just tiny pieces of the mantle.

The Crust

Earth’s crust is extremely thin, cold, and brittle compared to the other layers that lie below it. The crust is made of comparatively light elements, like silica, aluminum, and oxygen. It’s also highly varied in its thickness. Under the oceans, it may be as little as 5 kilometers thick. Beneath the continents, the crust may be 30 to 70 kilometers thick.

The inside of the crust is broken into big pieces, known as tectonic plates. These plates move slowly just at 3 to 5 centimeters per year. Scientists are still trying to understand this movement to its full extent. One theory is that it may be related to heat-driven convection currents in the mantle below. Whereas some scientists theorize it’s caused by the tug from slabs of the crust of different densities, something called “slab pull.” Over time, these plates will converge, pull apart or slide past each other. This movement of tectonic plates is what causes most earthquakes and volcanoes.