Scientists identify four bursts of fast true polar wander on Earth

A team at the University of Oslo led by Mathew Domeier found four episodes of true polar wander over the past 320 million years by tracking sea-level changes. Earth's surface shifted relative to its spin axis by up to 0.6 degrees per million years, faster than plate tectonics. The findings were published Oct. 1 in the journal Science.

• Four true polar wander episodes found: 190–200, 140–150, 90–100 and 30–20 million years ago
• Shifts reached 0.6 degrees per million years, faster than plate tectonics
• Method relies on a quadrupolar pattern of sea-level change between hemispheres
• A suspected event around 300 million years ago was ruled out as Pangea plate motion