New island forms in Tonga

The evolution of the newly-erupted "surtseyan" island ( 180 hectares in area) in the Kingdom of Tonga in the Southwestern Pacific is documented in a time-lapse sequences of perspective views using a time-series of DigitalGlobe WorldView images from just after the eruption ended in late January 2015 until late September 2017. These meter-resolution views were generated using Digital Elevation Models (DEMs) created by the NASA- led science team using stereo-pairs of DigitalGlobe Worldview images, and have allowed the erosional history of this unique island to be studied from a never-before-possible spaceborne perspective. The impact of marine abrasion on the somewhat fragile volcanic-ash landscapes is evident as the southern and southeastern margins of the new island, informally known as Hunga Tonga Hunga Ha'apai (HTHH), recede, while deposition of a widening isthmus grows to the northeast. Research results from NASA-funded science team led by James B. Garvin (NASA GSFC), Daniel A. Slayback (SSAI), Vicki Ferrini (Columbia) recently submitted for publication in the AGU's Geophysical Research Letters journal suggest the island's lifetime may be extended for another 25-30 years if geochemical fortification continues to protect key regions. The HTHH island is the first surtseyan eruption-based island to have persisted as "new land" for more than 6 months since Surtsey erupted near Iceland in 1963. Studies of the landscape evolution of pristine volcanic islands of this variety previously relied on a combination of aerial photography, field mapping, and laboratory sample analysis, but this new work enables an optimized approach via advanced satellite optical and radar imaging in combination with ship-based bathymetric mapping. Results of this work can be applied to understanding numerous small volcanic landforms on Mars whose formation may have been in shallow-water environments during epochs when persistent surface water was present. Field photography and sampling of the HTHH island "system" by French sailors who served as citizen geoscientists for the NASA project greatly enhanced the project and validated several key interpretations. (Special thanks to NASA Earth Sciences RRNES program, French sailors Damien Grouille and Cecile Sabau of the sailing vessel Colibri, and to the Schmidt Ocean Institute R/V Falkor).

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