China-led team reveals patterns in Earth's rotational deceleration over millions of years

Chinese researchers, in collaboration with counterparts from France, Germany and Ireland, have discovered that between 650 million and 280 million years ago, the Earth-Moon distance increased by approximately 20,000 km, and the length of a day extended by roughly 2.2 hours, the Science and Technology Daily reported on Tuesday.

The Earth's rotation has been slowing over time due to tidal dissipation, but the rate of this deceleration has not been consistently established, according to a relevant research article published in the journal Proceedings of the National Academy of Sciences (PNAS).

The researchers analyzed eight geological datasets to reconstruct the Earth's rotational history from 650 million to 240 million years ago. Their findings enabled them to test physical tidal models and identify a staircase pattern in the Earth's deceleration between 650 million and 280 million years ago.

Specifically, there are two periods with high Earth rotation deceleration, from 650 to 500 million years ago and from 350 to 280 million years ago, separated by an interval of stalled deceleration from 500 million to 350 million years ago.

These two periods roughly coincided with the Cambrian explosion and the largest mass extinction event in Earth's history, the article noted, adding that the two periods may have provided the necessary conditions for the evolution of early marine ecosystems.

Modeling indicated that, except for very recent times, tidal dissipation is the main driver for the deceleration of Earth's rotation, according to the research article.

The study has important theoretical significance for exploring the climate, environment and biological evolution due to Earth's rotation deceleration, said Ma Chao, a professor at the Chengdu University of Technology.

The team of researchers will further study the internal links between the Earth's rotation changes and natural phenomena such as the Earth's magnetic field, tidal actions and climate change in order to build a more comprehensive and accurate Earth system evolution model, Ma said.