The different evolution of recently grown volcanic islands in Tonga: two neighbouring volcanoes New Late&#8216;iki and Home Reef
Authors: Plank Simon , Ciancia Emanuele , Genzano Nicola , Pergola Nicola , Falconieri Alfredo , Martinis Sandro , Marchese Francesco 
Published: March 2024

Late&#8217;iki, formerly called Metis Shoal, and Home Reef are two active volcanoes located close to each other with a distance of approx. 23 km. Both volcanoes belong to the Tonga Volcanic Arc, west of the Tonga Trench in the South Pacific. During eruption processes, both volcanoes have produced ephemeral islands multiple times. The youngest volcanic islands were formed at Late&#8217;iki (called New Late&#8217;iki) during an eruption in mid-October 2019 and at Home Reef in September/October 2022. New Late&#8217;iki survived two months only, while the island at Home Reef survived over one year. Moreover, its area was even extended during a second eruption phase in September to November 2023. In this study, we analysed time series of multi-sensor satellite data in order to investigate the different evolution of the two youngest islands formed by the neighbouring volcanoes in 2019 and 2022, respectively. The information about the evolution of New Late&#8217;iki is taken from Plank et al. (2020), while recent multi-sensor satellite data have been analysed for the 2022/23 Home Reef eruption. Both islands, New Late&#8217;iki 2019 and Home Reef (2022), were formed during one single eruption phase. Analysis of MODIS and VIIRS visual and thermal data showed a 12-days long lasting eruption phase at New Late&#8217;iki in mid-October 2019 during which the island reached a maximum area of about 21,000 m&#178; (measured by Sentinel-2). Six weeks later, New Late&#8217;iki Island was completely reclaimed by the sea. The 2022 eruption at Home Reef was three times longer and produced an island with a maximum area of approx. 54,900 m&#178; (as measured on 8 October 2022). Comparing the evolution of the total island&#8217;s area, we see a 13 times faster erosion rate at New Late&#8217;iki compared to the one at Home Reef (until the beginning of the second eruption phase in September 2023). What caused the different evolution of the two neighbouring volcanic islands? Here, we will show how analysis of very high resolution (VHR) TerraSAR-X Starring Spotlight data (25 cm spatial resolution) supported by short wave infrared (SWIR) data from Sentinel-3 and HR imagery from Sentinel-2 and Landsat-8/9 satellites acquired over Home Reef provides more details to a better understanding of the evolution of volcanic islands. VHR radar data clearly shows a blocky structure developed at Home Reef, typical for a lava dome, i.e. very hard material robust against erosion. VHR TerraSAR-X data also enables to differentiate between the lava dome and the newly developed beach of unconsolidated material that was previously eroded from the lava dome.&#160;Reference:Plank, S., Marchese, F., Genzano, N., Nolde, M. &amp; Martinis, S. (2020): The short life of the volcanic island New Late&#8217;iki (Tonga) analyzed by multi-sensor remote sensing data. Scientific Reports 10, 22293. http://dx.doi.org/10.1038/s41598-020-79261-7