THE deep ocean continues to surprise: it appears a volcano on the seabed has exploded with a force thought impossible.
In 1999, the largest-ever swarm of quakes was recorded on a mid-ocean plate boundary, on the Gakkel Ridge in the east Arctic basin.
To find out what caused it, Robert Sohn of the Woods Hole Oceanographic Institution, Massachusetts, and colleagues peeked at the ridge with a remote-controlled device. They found shattered rock spread over 10 square kilometres, suggesting a series of volcanic explosions (Nature, vol 453, p 1236).
Such explosions can occur in shallow water if the water rapidly…
