Megaplume

A megaplume is a supermass of extremely hot rocks that moves very slowly under the surface of the earth and influences the breakup of tectonic plates.

The rise height of a buoyant plume increases with the discharge rate of its source fluid, and all previously observed hydrothermal plumes had been found no more than a few hundred meters above their sources. The megaplume reached a stunning 1,000 meters above the ridge axis depth of 2,300 meters.

Taken together, the two pieces of evidence could mean only one thing: the North Atlantic volcanoes were sitting atop a titanic, previously unknown hot spot, a megaplume of superheated magma rising from far down in the earth's mantle.

As well as these small continuous sources there exist much larger-scale episodes, which give rise to the so-called ‘megaplumes’.

"That's what I mean," Use said. "What if we emit an active sonar beam, one that's directionally very tight, at minimum power? Wave it back and forth and grab the micro-echoes off the precipitation particles? That would give a picture of water motion in the megaplume."