A massive floating mass of pumice stone discovered off of the New Zealand coast in July has been attributed to a massive eruption at the Havre Seamount, including the formation of a new volcanic cone.
New Zealand scientists mapped out the underwater volcano recently, while aboard the research vessel Tangaroa, reports Live Science.
Along with confirming the eruption of the Havre Seamount, the scientists also noted that there were two new volcano cones, one of which comes within 3,600 feet of the surface.
The eruption of the underwater volcano came on July 19 and sent pumice rocks floating to the surface. The pumice “raft” measured 8,500 square miles. It was discovered on August 9 by the HMNZS Canterbury ship. The floating island of lightweight rock measured 300 miles by 30 miles.
Lieutenant Tim Oscar, a Royal Australian Navy officer aboard the ship, observed that the floating fluffy-looking rock “lit up a brilliant white color” under a spotlight, “like the edge of an ice shelf.”
The Huffington Post notes that the researchers, from New Zealand’s National Institute of Water and Atmospheric Research (NIWA), stated that their findings, along with an analysis of satellite images from the floating mass, make a good case that the underwater volcano was the culprit.
Researchers mapped out the Havre Seamount in 2002 as well, using a multibeam echosounder, allowing them to compare images with the ones just taken this summer. NIWA marine geologist Joshu Mountjoy stated:
“The new map shows that the internal wall of the caldera now has up to 180 meters [590 feet] of lateral ‘bulging’ indicating the location of future eruption, or wall collapse.”
There were also two different types of magma that were expelled during the eruption. One of them, called rhyolite, is more explosive. It was likely responsible to shooting pumice to the ocean surface. The other, a less volatile one, settled down to build the new volcanic cones.
NIWA scientists have said that the pumice mat is still floating in thin areas. It will most likely take some time for the rocks to disperse completely.