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The Earth's core lies at the very center of the planet, playing an essential role in its structure and dynamics. From producing Earth's magnetic field to maintaining high temperatures, there are many Earth's core facts that explain its importance. In this article, we uncover 20 intriguing facts about Earth's core.1
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Earth’s interior is structured in several distinct layers. The outermost layer is the crust, which is underlain by the mantle, the thickest layer, Beneath the mantle lies the core, which is divided into two regions: the liquid outer core and the solid inner core. 1
The inner core is a hot, dense sphere predominantly made of iron, with a radius of about 1,220 kilometers (758 miles). It reaches temperatures of approximately 5,200°C (9,392°F) and is under nearly 3.6 million atmospheres of pressure. 2
Both the inner and outer cores are primarily composed of iron and nickel. The outer core, which extends from a depth of about 2,890 km to 5,150 km, is liquid and contributes to Earth’s magnetic field.
Some geoscientists refer to the outer core as Earth's "geodynamo." For a planet to possess a geodynamo, it must rotate, have a fluid medium in its interior, and the fluid must be electrically conductive. 3
The inner core is the Earth's innermost layer, playing a crucial role in generating the planet’s magnetic field through its interactions with the liquid outer core. As the Earth cools, the inner core is slowly growing at a rate of approximately 1 mm per year. 4
Direct observation of the inner core is impossible. The deepest drilling has only reached about 12 km, which remains within the crust, before the drill malfunctioned. This depth is far from reaching the core. 5
Studying the core is extremely challenging due to its inaccessibility. Most information comes from analyzing seismic waves and conducting high-pressure experiments in laboratories. 6
Earth's core formed about 4.5 billion years ago from molten iron and nickel. Over time, this mixture settled into a solid inner core and a liquid outer core. This differentiation was driven by the cooling of the planet and the gravity's effect on the molten materials. 7
Seismic waves from earthquakes travel through the core. Studying their behavior helps scientists infer details about the core's structure and composition. These waves reveal how the core's density and state vary with depth. 8
The core-mantle boundary is located about 2,900 kilometers (1,800 miles) below Earth's surface. This boundary separates the outer core from the mantle. It marks a significant transition in composition and physical state between the two layers. 9
The core releases heat into the mantle through thermal convection. This process is crucial for volcanic activity and mantle dynamics. It also drives the movement of tectonic plates on Earth's surface. 10
The inner core is denser than the outer core. The inner core’s density is about 12.8 g/cm³, compared to the outer core’s 9.9-12.2 g/cm³. This difference in density is due to the solid state of the inner core and the liquid state of the outer core. 11
Heat from the core drives convection currents in the mantle. These currents move tectonic plates, causing earthquakes and volcanic activity. This process also contributes to the formation of mountain ranges and oceanic trenches. 12
The inner core is younger than Earth. It began solidifying around 1 billion years ago, long after the outer core had already formed. The ongoing solidification of the inner core continues to release heat into the outer core and mantle. 13
Geoscientists believe that the iron crystals in the inner core are arranged in a hexagonal close-packed (hcp) pattern. These crystals align north-south, parallel to Earth's axis of rotation and magnetic field. 14
The orientation of the crystal structure in the inner core causes seismic waves—the most reliable method to study the core—to travel faster in the north-south direction compared to the east-west direction. 15
The growth of the inner core is not uniform; it occurs in lumps and bunches rather than steadily. This irregular growth is influenced by activities in the mantle, which impact the core's solidification patterns. 16
Growth tends to be more concentrated around subduction zones—regions where tectonic plates descend from the lithosphere into the mantle, thousands of kilometers above the core. 17
The core will never "freeze over" because the crystallization process is extremely slow, further delayed by the ongoing radioactive decay of Earth's interior. Scientists estimate it would take about 91 billion years for the core to fully solidify. 18
Geoscientists have recently discovered that the inner core contains an even smaller core, known as the inner inner core. This inner inner core differs from the main inner core in a similar way that the inner core differs from the outer core.
