New Insights Reveal Rapid Shifts in Earth's Rotation Axis

One of the most dramatic processes in Earth's history remains largely invisible and heavily debated among scientists. True polar wander involves the entire surface of the planet shifting in a massive rotational movement relative to its axis of rotation. While the scars of colliding continents or opening and closing oceans remain recognizable billions of years later, the tipping of the Earth as a whole leaves very few direct marks in the rock record.

Using a refined analysis of past sea level changes, a research team led by Mathew Domeier from the University of Oslo has reportedly detected such events in the distant past. According to their findings published in the journal Science, the Earth's surface has shifted drastically and rapidly relative to its rotational axis on multiple occasions.

Experts have long suspected that true polar wander is not uniform but occurs in irregular bursts. The Earth is capable of tipping because its mass distribution varies over time. In a rotating body, the moment of inertia is typically aligned symmetrically with the axis of rotation to maintain the lowest energy state. However, processes within the mantle and drifting continents gradually alter this moment of inertia, requiring the mantle and surface to constantly realign.

Currently, this polar wander progresses at a rate of about ten centimeters per year. However, researchers suggest that imbalances may accumulate over time and resolve rapidly over tens of millions of years, reaching speeds of several dozen centimeters annually. Such rapid shifts would have drastic effects on climate and life, as climate zones are tied to the rotational axis, potentially moving a region from a temperate zone into the tropics within a short period.

Proving these events has historically been difficult because most methods rely on the paleomagnetic orientation of rocks, which makes it challenging to distinguish whole-Earth rotation from continental drift. To bypass this, Domeier's team analyzed sea level fluctuations relative to continents in ten-million-year steps. They identified two periods where the expected pattern matched data: one between 150 and 140 million years ago, and another around 100 million years ago.

Meanwhile, separate research focusing on the Pacific floor offers additional clues regarding a later period. Magnetic patterns in the ocean crust suggest that the solid Earth body reoriented itself by six to seven degrees relative to its rotation axis between 56 and 48 million years ago, translating to a shift of roughly 500 miles. Led by Professor Richard G. Gordon of Rice University, this study also helps explain the mysterious bend in the Hawaiian-Emperor seamount chain.

The Hawaiian islands form the youngest end of a long chain of extinct volcanoes created as the Pacific Plate moves over a mantle hotspot. The prominent bend in the chain, dating back about 47 million years, has long sparked debate over whether the Pacific Plate abruptly changed course or the mantle plume itself migrated. By determining a new magnetic reference point for the Pacific from 56 million years ago, the Rice University researchers provided vital context to help resolve the debate.