Tongan volcanic island unofficially named Hunga Tonga-Hunga Haapai was initially only expected to stay above sea level for a matter of months
A new Tongan island formed from the ash of a 2014 volcanic eruption in the South Pacific could exist for decades, according to a study released by Nasa.
The ash island, unofficially named Hunga Tonga-Hunga Haapai, formed during a submarine volcanic eruption that lasted from late December 2014 to early January 2015. The new land mass, which has a 120m summit, was originally only predicted to last months.
Instead, Nasa now believes Hunga Tonga-Hunga Haapai will remain for between six and 30 years, making it the first island of this type to persist in the modern satellite era.
Nasa has observed the island since its formation, making monthly high-resolution satellite observations using both optical sensors and radar. Observing Hunga Tonga-Hunga Haapai has allowed Nasa to build a picture of how new islands are formed and shaped over time.
Volcanic islands are some of the simplest landforms to make, said Jim Garvin, first author of the study and chief scientist of Nasas Goddard space flight centre.
Our interest is to calculate how much the 3D landscape changes over time, particularly its volume, which has only been measured a few times at other such islands. Its the first step to understand erosion rates and processes and to decipher why it has persisted longer than most people expected.
The island has also given researchers insights into similar features in other parts of the solar system, including Mars.
Everything we learn about what we see on Mars is based on the experience of interpreting Earth phenomena, Garvin said. We think there were eruptions on Mars at a time when there were areas of persistent surface water. We may be able to use this new Tongan island and its evolution as a way of testing whether any of those represented an oceanic environment or ephemeral lake environment.
The imagery has also been used to make three-dimensional maps of the islands topography, allowing researchers to study its changing coastlines and volume above sea level.
In May 2016, researchers thought Hunga Tonga-Hunga Haapai was disintegrating when the ocean washed over the south-eastern rim of the interior crater wall, opening the crater lake.
However, by June a sandbar had formed and the island continued to stabilise throughout the year.
Scientists arent certain why Hunga Tonga-Hunga Haapai has lasted so long, but a similarly formed island off Iceland, called Surtsey, may provide clues. Warmed seawater interacted with ash after the eruption that formed Surtsey, chemically altering the islands fragile and easily eroded rock and turning it into a tougher material. Researchers suspect something similar might have happened to its South Pacific counterpart.
Exactly how long Hunga Tonga-Hunga Haapai persists will depend on environmental factors, including wave erosion, according to Nasa.
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