Scientists developed a computer model to identify four possible instances of true polar wander in the past. And, they say, true polar wander is happening now.
Scientists based in Germany and Norway today published new results about a geophysical theory known as true polar wander. That is a drifting of Earth’s solid exterior – an actual change in latitude for some land masses – relative to our planet’s rotation axis. These scientists used hotspots in Earth’s mantle as part of a computer model, which they say is accurate for the past 120 million years, to identify four possible instances of true polar wander in the past. And, they say, true polar wander is happening now. These scientists published their results in the Journal for Geophysical Research today (October 1, 2012).
The scientists – including Pavel V. Doubrovine and Trond H. Torsvik of the University of Oslo, and Bernhard Steinberger of the Helmholtz Center in Potsdam, Germany – established what they believe is a stable reference frame for tracking true polar wander. Based on this reference frame, they say that twice – from 90 to 40 million years ago – the solid Earth traveled back and forth by nearly 9 degrees with respect to our planet’s axis of rotation. What’s more, for the past 40 million years, the Earth’s solid outer layers have been slowly rotating at a rate of 0.2 degrees every million years, according to these scientists.