Recently, groundbreaking research has suggested that the Earth’s inner core, previously thought to rotate faster than its surface, may have slowed down. This surprising shift has potential ramifications for our understanding of the planet’s evolution and dynamics.
Highlights of the Recent Research
To establish this conclusion, researchers analyzed seismic waves from repeated earthquakes spanning the last six decades – a seminal methodology in the field. Alterations in the time and propagation of these signals provided an estimate of the inner core’s rotation. This innermost layer of Earth is believed to operate independently from the mantle and the rest of the planet.
According to the findings, the inner core began rotating at a slightly higher speed than the rest of the planet in the early 1970s. However, this pace decreased until it achieved parity with the Earth’s rotation around 2009. Since then, the inner core has exhibited a “negative trend,” indicating that it is now rotating slower than the surface. Researchers predict the next significant change may occur in the mid-2040s, suggesting the Earth’s inner core alters its speed every 60-70 years on average.
Significance of the Study
This study holds broad implications for Earth science. It may inspire researchers to construct and test models that treat the Earth as a single dynamic system. Additionally, the deceleration could affect the speed at which the entire planet spins, and influence the evolution of the core over time.
A Closer Look at Earth’s Inner Core
The Earth’s inner core, a solidified iron ball roughly the size of Pluto, constitutes the Earth’s innermost layer. Its solidity is due to the extreme pressure exerted by the Earth’s other layers. Unlike the liquid outer core, the inner core, situated approximately 5,000 kilometers (3,100 miles) beneath our feet, can spin independently as it floats in the molten outer core. The inner core has an average radius of 1220 km, with the boundary between the inner and outer core — known as the Lehman Seismic Discontinuity — located at approximately 5150 km below the Earth’s surface. Temperature within the inner core ranges between 7,200–8,500ºF (4,000–4,700ºC), and it is projected to exhibit high thermal and electrical conductivity.
The Three Layers of Earth
The Earth is composed of three primary layers: the crust, the mantle, and the core. The crust consists primarily of solid rock, such as basalt and granite. The mantle, a layer of hot, dense, iron and magnesium-rich solid rock, extends up to 2900 km in thickness beneath the crust. At the Earth’s center is the core, composed of two sections: the liquid outer core, containing nickel, iron, and molten rock; and the solid inner core.
Review Questions from UPSC Civil Services Examination
Past UPSC examinations have featured questions related to this topic. For example, in prelims (2009), a question was asked: “In the structure of planet Earth, below the mantle, the core is mainly made up of which one of the following? (a) Aluminium (b) Chromium (c) Iron (d) Silicon.” The answer is c) Iron. In the mains (2018), candidates were asked to “Define mantle plume and explain its role in plate tectonics.”