Overview
- Published March 19 in Science, the Harvard-led study analyzed more than 900 samples from over 100 East Pilbara sites using step-heating and ultra-sensitive magnetometry to isolate ancient magnetic signals.
- Paleomagnetic data indicate the Pilbara block shifted from roughly 53° to 77° in latitude and rotated more than 90° over about 30 million years, with motion on the order of tens of centimeters per year before slowing.
- Comparisons with prior work in South Africa’s Barberton Greenstone Belt, which stayed near the equator and was nearly stationary, show differential motion between cratons at the time.
- The team documents the oldest-known geomagnetic reversal at around 3.46 billion years ago, with evidence suggesting reversals were less frequent than in more recent Earth history.
- The results eliminate a globally immobile ‘stagnant lid’ at 3.5 billion years ago yet leave unresolved whether early Earth operated in a sluggish, episodic, or modern-style active lid regime, with implications for early life preserved in Pilbara rocks.