THE geological scar left by the devastating earthquake off the coast of Sumatra in December 2004 has healed more quickly than expected.
Satellite measurements of Earth’s gravitational field taken just after the quake show it left a depression 8 millimetres deep in the crust and shallow mantle. While this doesn’t seem like much, the shifting mass jolted Earth’s axis of rotation enough to move the poles by 10 centimetres.
In under a year, however, the depression had nearly vanished – something that surprises geologists, because according to models of how rocks in the mantle move it should have taken 20…
