Mystery of the Floating Pumice Island Solved!

It was really an underwater volcanic eruption, but then that was already known. What wasn’t known was which underwater vent it was that caused this huge pumice spread. Samples were taken from the unusual island and analysed. Now, a source has been identified.

We reported the news here:

The floating island of pumice.

One suspect ruled out, another implicated

Many volcanologists have suggested that an active seamount, the Monowai seamount, erupting along the Kermadec arc was responsible for the huge emission of the light rock. The problem is with the alibi – the island was reportedly spotted as early as 1st of August by an airline pilot, while Monowai erupted only on the 3rd of August. Ruling out time travel, the only logical explanation seems to be another source, a bit farther away.

The offender has been pinpointed as the Havre Seamount, says volcanologist Erik Klemetti, assistant professor of geosciences at Denison University. The data going into this analysis comprises pictures from the Moderate Resolution Imagine Spectrometer (MODIS) aboard the Terra and Aqua satellites and accurate depth mapping of the seabed. Ocean bathymetry, or seafloor topography, maps out the physical features of the seafloor. An erupting underwater volcano is like a new pimple on the face of the seafloor.

How they did it

The seafloor map revealed a volcanic plume and the MODIS images from the 19th of July revealed high ash content in the water and also some pumice in and around the Havre seamount. The MODIS thermal images from a day, taken at 10:50 PM, before revealed a lot of heat in the region, indicating that the volcano was erupting. The eruption was strong enough to breach the surface in under 12 hours, which means penetrating a column of water more than a kilometer in height.

The Havre seamount activity receded around the 21st of July, but, by then, it left off enough pumice residues to create the huge island that was seen.

First hand look

But people are still not satisfied. They want to view the Havre eruption first hand, after going down to the seafloor in a research vessel and photographing the area.

It has been speculated that such underwater vents spewing out pumice can be responsible for replenishing the pumice content in the coral reefs around the world.

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Debjyoti Bardhan

Is a science geek, currently pursuing some sort of a degree (called a PhD) in Physics at TIFR, Mumbai. An enthusiastic but useless amateur photographer, his most favourite activity is simply lazing around. He is interested in all things interesting and scientific.