PNNL

Abstract

We have monitored a newly-erupted surtseyan volcanic island in the Kingdom of Tonga, unofficially known as Hunga Tonga Hunga Ha’apai (HTHH), by means of very high-resolution satellite observations. The new ~1.8 km2 island formed as a tuff cone over the course of a month-long hydro-volcanic eruption in early 2015 in the Tonga-Kermadec Islands volcanic arc. Such tephra-dominated eruptions usually produce fragile subaerial landscapes that wash away rapidly due to marine abrasion, as documented in 2009. Our measured rates of erosion are five to twenty times greater than observed at Surtsey (Iceland). Preliminary measurements of the topographic expression of the primary tuff cone from the past ~ 30 months suggest an extended lifetime of at least ~ 6.5 years (and potentially up to 29 years), documenting details of its landscape evolution using satellite and ship-based remote sensing approaches never-before available at such scales for this type of newly-formed island. A new volcanic island in the southwestern Pacific Ocean that formed by means of an eruption style similar to that of Surtsey (Iceland) was monitored and observed via high resolution satellite imaging for over ~30 months since its time of formation in early 2015. This island, unofficially named Hunga Tonga Hunga Ha'apai (HTHH), was not expected to persist as land for more than a few months, but our observations have documented its lifetime for 30 months. Using topography derived from high resolution satellite images, the above-sea-level volume of the island was measured over time, leading to a "volumetric" erosion rate that was compared with other oceanic islands. The HTHH island is disappearing five times (or more) faster than Surtsey, but much slower than typical models predict, allowing detailed measurement of its erosional history at new spatial scales. Regional submarine topography (bathymetry) shows that shallow-water topology may be an important factor in explaining the unexpected lifetime of this new island, together with the likelihood of internal strengthening by hydrothermal mineralization. The stages of erosion of the HTHH island may have implications for similar landforms discovered on Mars and their formation and evolution.