Cyclostratigraphic reconstruction of k and its trends over time. Credit: Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2317051121
A multi-institutional team of geoscientists has found evidence that Earth’s rotation is slowing in a staircase pattern, with two distinct stable periods. In their study, published in the journal Proceedings of the National Academy of SciencesThe group analyzed data from sediment samples dating back more than half a billion years.
Previous research has shown that Earth’s axial rotation is slowing, primarily due to tidal dissipation, but as the researchers in this new initiative noted, the rate of deceleration has not been consistently mapped. In this initiative, they attempted to do so by going back 650 million years.
The researchers analyzed eight geological datasets compiled over several decades. These sedimentary archives provide information not only about geographical history, but also about the history of the Earth’s rotation. The datasets cover the period from 280 to 650 million years ago.
The timeline reveals that the slowdown was not smooth. Instead, Earth experienced a series of slowdowns followed by periods of stability, resulting in a staircase pattern. The researchers also found two notable periods of stability, one that coincided with the Cambrian explosion, which led to a massive increase in wildlife diversity, and another that coincided with the largest known mass extinction. They suggest that the periods following both slowdowns may have been more than coincidences.
The data also confirmed that, except in modern times, when humans have disrupted the global environment, the deceleration has been due to tidal dissipation – the dissipation of orbital and rotational energy as heat on the ocean surface, in the planet’s interior, or on the Moon. Tidal heating occurs as the Moon stretches and compresses as it moves closer to Earth.
The research team also found that during the period studied, the distance between the Moon and Earth was about 20,000 kilometers greater than it is today, and Earth days were about 2.2 hours longer. The research team plans to continue its work by looking for links between changes in Earth’s rotation and major environmental events.
More information:
He Huang et al., Geological evidence reveals a staircase model in the evolution of Earth’s rotational deceleration, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2317051121
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