The core of Earth is the central part of our planet, lying beneath the mantle and making up about one-third of Earth’s total mass. It is divided into two distinct parts: the outer core, which is liquid, and the inner core, which is solid. The core is composed mainly of iron and nickel, with traces of lighter elements.
Structure of the Outer Core
The outer core extends from about 2,900 km to 5,100 km below Earth’s surface. It is made of molten iron and nickel and is in constant motion due to convection currents. These movements generate Earth’s magnetic field through the geodynamo effect. Temperatures here range between 4,000 °C and 6,000 °C, making the metals fluid despite the immense pressure.
Structure of the Inner Core
The inner core lies at the very center of Earth, starting around 5,100 km deep and extending to Earth’s center at 6,371 km. Unlike the outer core, it is solid due to the extreme pressure that prevents atoms from moving freely, despite temperatures estimated to exceed 6,000 °C. The inner core is thought to grow slowly as the outer core cools and solidifies over geological time.
How Scientists Determined the Core’s Structure
Scientists cannot directly observe Earth’s core, but they discovered its nature through seismic waves generated by earthquakes. Seismic waves travel at different speeds through solids and liquids. By studying how these waves bend, reflect, and sometimes fail to pass through certain regions, scientists deduced the existence of a liquid outer core and a solid inner core.
Key Discoveries in Core Science
- In 1906, Richard Dixon Oldham showed that Earth has a central core by analyzing seismic wave paths.
- In 1936, Inge Lehmann, a Danish seismologist, discovered the solid inner core by detecting how certain waves reflected inside Earth.
- Modern seismic tomography and supercomputers now allow detailed modeling of the core’s dynamics, confirming its composition and role in generating the magnetic field.
Why the Core Matters
The core is vital to life on Earth. The liquid outer core drives the geodynamo, which creates the magnetic field that shields Earth from harmful solar radiation. Without it, our atmosphere and oceans could be stripped away by solar winds, making Earth uninhabitable.
Conclusion
Earth’s core, though unreachable, is one of the most studied parts of our planet thanks to seismic science. It consists of a liquid outer core and a solid inner core, both made mostly of iron and nickel. The discovery of the core not only deepened our understanding of Earth’s structure but also revealed its role in sustaining life by protecting the planet with a magnetic shield.
Glossary
- Outer core – liquid layer of iron and nickel located beneath the mantle.
- Inner core – solid sphere of iron and nickel at the planet’s center.
- Seismic waves – vibrations from earthquakes used to study Earth’s interior.
- Geodynamo – process in which fluid motion in the outer core generates Earth’s magnetic field.
- Seismic tomography – imaging technique using seismic waves to model Earth’s interior.
- Magnetic field – invisible field around Earth that protects it from solar radiation.
