Live Science
The center of the Earth is located about 6,400 km below our feet. To put that in context, the deepest humans have ever drilled is 12.2 km, and it took geologists about 20 years to reach that limit.
Fortunately, scientists don’t have to drill into our planet to study it. By measuring seismic waves traveling through Earth, scientists have developed a solid understanding of its basic internal structure.
What is inside the earth?
Planet Earth generally consists of a crust, mantle (core), and core. The crust hosts all known life forms, but it is just the Earth’s outer shell, representing only 1% of the planet’s total volume. The mantle, or core, or middle layer, makes up 84% of the Earth’s volume, and the inner layer, the core, makes up the last 15%, according to the University of Illinois Urbana-Champaign.
Dandruff
The crust is divided into oceanic crust and continental crust. Oceanic crust is 5 to 10 km (3 to 6 miles) thick and lies beneath the oceans, while continental crust is up to 80 km (50 miles) thick, according to the Sesmin project at University College London.
Oceanic crust is composed mostly of basalt rock, and is denser than continental crust, which is largely composed of granite. So when an oceanic plate collides with a continental plate, the denser oceanic crust moves beneath the continental crust, according to the Space website. This process takes a long time, but it eventually sends the oceanic crust into the mantle at a rate of 2 to 8 centimeters per year, according to the US Geological Survey.
The scarf
The mantle is not liquid, but it is less solid than sinking oceanic crust, Sunyoung Park, an assistant professor who studies the Earth’s internal structure at the University of Chicago, told Live Science. “On the geological time scale, it appears almost like a liquid, even though it is a solid rock,” she added.
Park noted that the mantle is composed of different minerals, but bridgmanite is likely the most abundant.
This part of the Earth extends to a depth of about 2,900 kilometers (1,800 miles), according to the Sesmin project, and there is an upper mantle and a lower mantle.
The Earth’s internal temperature rises between the boundaries of the upper mantle and the bottom of the lower mantle, and ranges from 1,000 to 3,700 degrees Celsius (1,800 to 6,700 degrees Fahrenheit), according to the Space website.
Nucleus
A 2,300 km (1,400 mi) thick sea of molten iron and nickel marks the beginning of the Earth’s core. This liquid sea, known as the outer core, surrounds a mostly solid iron sphere — about 2,440 km (1,520 miles) across — called the inner core. The outer core of liquid iron revolves around the inner core, giving the Earth its magnetic field.
Our planet formed about 4.6 billion years ago, and as it cooled, heavier elements such as iron and nickel migrated inward to form the core.
Park said the Earth’s interior is still cooling, and as that happens, the inner core continues to form.
According to Park: “Just as water turns into ice, iron solidifies and turns into an inner core, so the inner core actually grows.” She added that it grows slower than a human fingernail.
The temperature of the inner core is about 5,200 degrees Celsius (9,400 degrees Fahrenheit), roughly equivalent to the temperature of the sun’s surface, but the enormous pressure keeps it mostly solid. Inside the inner core is the innermost core, a solid metal sphere 725 km (450 miles) across.
