Unfortunately, Jules Verne’s story is just fiction. Such an amazing subterranean world as he describes does not exist. The depth where his characters find the central sea is in reality, the region of the upper mantle and quite inhospitable if anyone where ever to reach its depth. (The deepest we’ve been able to reach is 7miles/12 km, in a well drilled by the Soviet Union in the Kola Peninsula.) The earth we now know is a solid sphere with several different layers making up its composition. We live on a very thin portion of these layers, known as the crust. The other layers we have learned are composed of solid and liquid rock, making up the mantle and the core. As an analogy, we can think of the Earth as a coconut. A coconut has a tough, but thin, outer shell, analogous to the crust. The white meat of the coconut is like the earths mantle. Finally, the coconut milk found in the center of the nut is similar to the liquid outer core of the earth.
We know quite a bit about the center of our planet, even though no man has ever journeyed as far as the fictional adventures put forth by Jules Verne. Nearly all of our knowledge about the center of the earth comes from interpreting seismic waves as they travel through the planet. We will begin our own journey through the layers of the earth at the center, starting with the core.
Unlike our coconut analogy, the core of the earth is not one single liquid structure, but two separate structures, one liquid, the other solid. The Inner Core is solid and is composed of an iron-nickel alloy. It has a radius of 1215 kilometers (km), extending from 6370 km (the center of the earth) to 5155 km. It is also very dense, nearly 13 times as dense as water. Estimates put the temperature of the inner core at 8100 degrees Fahrenheit (4500 degrees Celsius). Surrounding the solid inner core is the outer core. The Outer Core is liquid and composed of an iron-sulfur mixture. This liquid core is in constant motion and it is this convection that produces the magnetic field of the Earth. The outer core is nearly twice as thick as the inner core (2255 km), extending from 5155 km to 2900 km. Despite the fact that it is a liquid, the outer core is actually cooler than the inner core, reaching only to 5700 degrees F (3200 degrees C). The core (both inner and outer) accounts for 31 percent of the Earth’s mass.
