Deep-sea volcano eruption seen for first time

Marine geologists have the first-ever measurements of the eruption of a deep-sea volcano after a sensor was accidentally caught up in one.

The device, nicknamed a rumbleometer, was feared lost when the sea mount it was supposed to be monitoring erupted.

Although the aftermath of undersea eruptions have been studied, none had been 'seen' because of the time research ships take to get to the site.

The rumbleometer was intended to measure tiny vertical movements as magma shifts around beneath the Axial volcano, 300 miles off the west coast of North America.

The sequence of events was entirely fortuitous and "absolutely unique", admits geophysicist Christopher Fox.

"We didn't put these things out with the intention of having them caught up in lava flows," he says.

The data - obtained after a dramatic rescue effort involving a research ship and a robotic submarine - yielded "very, very, accurate" measurements of lava flowing from the volcano.

When Axial erupted in January 1998, the sensor recorded being lifted up nearly three metres on a bubble-like crust of lava.

It was held aloft for less than an hour before the bubble collapsed when the lava beneath it drained away, it was reported.