Earth's Inner Core Rotation Has Paused and Reversed Direction, Researchers Find

Researchers have discovered an unusual phenomenon in the Earth’s inner core: a change in its rotational direction after a period of deceleration. Findings published by a team from Peking University in China indicate that this dynamic occurs over a multi-decade timescale. The research is expected to help understand what is happening deep inside the planet and its effects on the surface. Seismologists Yi Yang and Xiaodong Song, the study’s authors, observed seismic waves travelling through the Earth. They analysed differences in waveform shape and travel time from earthquakes occurring between 1990 and 2021. The results were striking. Before 2009, the inner core’s rotation was slightly faster than that of the Earth’s surface and mantle. However, the movement then slowed and paused for several years. The research team also suggested their findings could be linked to a reversal of the inner core’s rotation occurring on a roughly seven-decade cycle, with a similar event having taken place in the early 1970s. According to the researchers, the fluctuation in the core’s rotation aligns with several periodic changes, resulting from interactions between the Earth’s different layers. One potential impact of this phenomenon is a slight variation in the length of a day experienced on the surface. The Earth’s core consists of two layers: a liquid outer core and a solid inner core composed of rotating iron.