HOW CLOSE TO THE EARTH’S CORE CAN WE DIG?

Digging far towards the Earth’s core is obviously a difficult task. But what is the maximum depth humans can attain?

Earth’s core. Image credit: Argonne National Labs

What is inside the Earth’s core?

The Earth’s core consists of two fundamental layers: the inner core and the outer core.

1. Inner Core

The inner core is a solid, dense sphere at the center of the Earth, with a radius of about 760 miles (1,220 kilometers).

Composed mainly of iron and nickel, it is estimated to have temperatures reaching up to 9,000 degrees Fahrenheit (5,000 degrees Celsius) due to the immense pressure exerted by the layers above. Despite these extreme temperatures, the inner core remains solid due to the high pressure, which prevents the iron and nickel atoms from rearranging into a liquid state.

The solid inner core is thought to have formed as a result of gradual cooling of the Earth’s interior over billions of years, causing the molten iron and nickel in the outer core to crystallize. This process is believed to have started approximately 1 to 1.5 billion years ago. As the inner core continues to cool, it grows at a rate of about 0.04 inches (1 millimeter) per year, primarily by the solidification of the liquid outer core.

The inner core’s solid state has important implications for Earth’s seismic activity and magnetic field. Seismic waves generated by earthquakes travel through the Earth and are influenced by the properties of the inner core. By studying how seismic waves propagate through the inner core, scientists can gain insights into its composition, temperature, and density, which helps refine our understanding of Earth’s interior structure and dynamics.

Despite its extreme conditions, the inner core remains largely inaccessible to direct observation or measurement. Scientists rely on indirect methods, such as seismic tomography and computational models, to study its properties and behavior.

2. Outer Core

Surrounding the inner core is the outer core, a layer of molten metal that extends from the inner core to a depth of about 1,800 miles (2,900 kilometers).

Like the inner core, the outer core is predominantly composed of iron and nickel, with smaller amounts of lighter elements such as sulfur and oxygen.

The outer core is in a state of constant motion, undergoing convection currents driven by heat released from the solidification of the inner core and radioactive decay in the Earth’s mantle. This convective motion generates Earth’s magnetic field through a process known as the geodynamo effect.

As the molten iron and nickel in the outer core move and flow, they generate electric currents, which in turn produce magnetic fields. The combined effect of these magnetic fields gives rise to Earth’s global magnetic field, which extends far into space and serves as a protective shield against solar radiation and cosmic particles.

The outer core’s role in generating Earth’s magnetic field has significant implications for life on our planet. The magnetic field deflects charged particles from the Sun, preventing them from stripping away the Earth’s atmosphere and protecting life from harmful radiation. It also acts as a fundamental basis used by humans in navigation, allowing compasses to align with the magnetic field lines and providing sailors and travelers with a reliable means of orientation.

Despite its importance, the outer core remains one of the least understood regions of the Earth’s interior. Its extreme conditions, including high temperatures and pressures, make it inaccessible for any direct observation or measurement. Scientists rely on a combination of laboratory experiments, computer simulations, and indirect observations, such as geomagnetic data and seismic wave analysis, to study the outer core’s properties and behavior.