550 / 2024-09-18 11:59:02

Geological evidence reveals a staircase pattern in Earth’s rotational deceleration evolution

Earth-Moon system, Earth’s rotation, cyclostratigraphy, tidal dissipation, geological evolution

Session 42 - Deep-time ocean and climate changes: insights from models and proxies

The Earth’s rotation has been decelerating throughout its history due to tidal dissipation, but the variation of the rate of this deceleration through time has not been established. We present a detailed analysis of eight geological datasets to constrain the Earth’s rotational history from 650 to 240 million years ago. The results allow us to test physical tidal models and point to a staircase pattern in the Earth’s deceleration from 650 to 280 million years ago. During this time interval, the Earth-Moon distance increased by approximately 20,000 km and the length of day increased by approximately 2.2 hours. Specifically, there are two intervals with high Earth rotation deceleration, 650 to 500 million years ago and 350 to 280 million years ago, separated by an interval of stalled deceleration from 500 to 350 million years ago. The interval with stalled deceleration is attributed mainly to reduced tidal dissipation due to the continent-ocean configuration at the time, not to changes in Earth’s dynamical ellipticity from continental assembly or glaciation. Modeling indicates that, except for the very recent time, tidal dissipation is the main driver for decelerating Earth rotation. One potential implication of our findings is that the Earth’s tidal dissipation, along with Earth’s rotation deceleration, may play a role in the evolving Earth.