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Abstract On 15 January 2022, Hunga volcano erupted, creating an extensive and high-reaching umbrella cloud over the open ocean, hindering traditional isopach mapping and fallout volume estimation. In MODIS satellite imagery, ocean surface water was discolored around Hunga following the eruption, which we attribute to ash fallout from the umbrella cloud. By relating intensity of ocean discoloration to fall deposit thicknesses in the Kingdom of Tonga, we develop a methodology for estimating airfall volume over the open ocean. Ash thickness measurements from 41 locations are used to fit a linear relationship between ash thickness and ocean reflectance. This produces a minimum airfall volume estimate of$${1.8}_{-0.4}^{+0.3}$$ km3. The whole eruption produced > 6.3 km3of uncompacted pyroclastic material on the seafloor and a caldera volume change of 6 km3DRE. Our fall estimates are consistent with the interpretation that most of the seafloor deposits were emplaced by gravity currents rather than fall deposits. Our proposed method does not account for the largest grain sizes, so is thus a minimum estimate. However, this new ocean-discoloration method provides an airfall volume estimate consistent with other independent measures of the plume and is thus effective for rapidly estimating fallout volumes in future volcanic eruptions over oceans.
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This content will become publicly available on March 16, 2027
Volcanic Ash Affected by Lightning During the Hunga 2022 Eruption
Abstract The 15 January 2022 eruption of Hunga volcano (Kingdom of Tonga) produced the most lightning ever documented during an explosive eruption to date. This study estimates the mass of erupted tephra that may be structurally or electromagnetically affected by the lightning, based upon lightning peak current, channel length, and ash plume particle concentration. The lightning channels totaled 1.67 million m3in volume and contained 548 kg of volcanic ash at a calculated plume concentration of 0.328 g/m3. From this total, 54.8 kg of ash may display physical evidence in the form of lightning‐induced textures, such as lightning‐induced volcanic spherules, but this is an insignificant fraction of the total airfall deposit (10−8%). However, the total mass of ash exposed to magnetic flux densities exceeding Earth's ambient surface values is 2.24 × 1014 g, corresponding to just over a third (34.9%) of the calculated mass of total airfall (5.21 × 1014 g). This study reveals that even though physical evidence of volcanic lightning may be limited, ash particles will still be affected by the electromagnetic fields generated by the lightning discharge. The extent of these effects will be a function of lightning properties, ash properties, and location of the ash in relation to the discharge channel.
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- Award ID(s):
- 2151806
- PAR ID:
- 10673137
- Publisher / Repository:
- American Geophysical Union
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 131
- Issue:
- 5
- ISSN:
- 2169-897X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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