A Young Island in the South Pacific Oozes Mysteries and Mud

It offers clues to unanswered questions about how volcanic landscapes form.

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NASA/Dan Slayback

It’s not every day scientists get the chance to walk on a volcanic island shortly after it erupts from the ocean. But that’s what research scientist Dan Slayback got to do during his visit to a small group of islands in the South Pacific. Slayback, of NASA’s Goddard Space Flight Center in Maryland, joined a group of scientists and students with the Woods Hole Sea Education Association (SEA) to investigate first-hand a three-year-old landform he’d been observing via satellite off the coast of the island nation of Tonga.

Geologically speaking, three years is hardly a blip, and islands of this kind often don’t last for more than a few months due to ocean erosion. This island, temporarily named Hunga Tonga-Hunga Ha’apai (HTHH for short) after the older islands surrounding it, is one of only three in the past 150 years that have survived this long. Clues to its staying power may lie in the thick mucky clay washing out of the island’s cone and down its deeply furrowed flanks.

HTHH erupted from a submarine volcano in late December 2014. By January 2015, the ash had settled, revealing a new island with a summit 400 feet high and a base about three miles across. What look like shallow grade beaches on NASA satellite images are in fact steep, gravelly shores not well suited for smooth landings—or open-toed footwear for that matter. “Most of it is this black gravel … pea sized gravel,” notes Slayback documenting the expedition, “and we’re mostly wearing sandals so it’s pretty painful.”

This was the first of many useful lessons about the difference between studying the landform from space and studying it from the ground. The crater lake, for example, is surrounded by dramatic canyon-like gulches, the result of erosion from rainfall. As the island grows, it’s also getting scoured away. “It’s another aspect that’s made very clear when you’re standing in front of these huge erosion gullies,” says Slayback. “Okay, this wasn’t here three years ago, and now it’s two meters deep.” Add that to the constant wave erosion and you begin to understand why many volcanic newborns are short-lived.

Another surprise was the discovery of flowering vegetation that had taken root on the volcanic cone and in the mud of the isthmus connecting HTHH to its neighbor. Where did the seeds come from? Most likely from bird droppings; a whole colony of sooty terns had taken up residence among the cliffs surrounding the lake.

Slayback’s primary goals were to collect soil and rock samples for chemical analysis at Goddard’s Nondestructive Evaluation Lab and to determine the island’s true elevation. Using stable and mobile GPS devices, the team recorded upwards of 150 elevation and location measurements, which will be combined with drone survey footage and satellite imagery to create a 3D model of the island.

From there, Slayback can calculate how much volcanic material it took to create the island and perhaps learn about any hydrothermal processes still at work, and whether they might generate a substrate resistant to erosion. If so, this baby island could survive into adolescence, and possibly into adulthood, according to .

Understanding how new islands form on earth can help scientists learn more about how volcanic landscapes may have evolved on ancient Mars (there’s the NASA connection). But this muddy little hunk of terra firma in the South Pacific presents enough unsolved mysteries to keep Slayback busy for a while. He’ll return next year for further study, with a sturdier pair of shoes.

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