Abstract
Submarine volcanism in shallow waters (<100 m), particularly in remote settings, is difficult to monitor quantitatively and, in the rare formation of islands, it is challenging to understand the rapid-paced erosion. However, these newly erupted volcanic islands become observable to airborne and/or satellite remote sensing instruments. NASA’s ICESat-2 satellite laser altimeter, combined with visible imagery (optical and microwave), provide a novel method of evaluating the elevation characteristics of newly emerged volcanoes and their subaerial eruption products. Niijima Fukutoku-Okanoba (NFO) is a submarine volcano 1300 km south of Tokyo (Ogasawara Archipelago of Japan) that periodically breaches the ocean surface to create new islands that are subsequently eroded. The recent eruption in August 2021 is a rare opportunity to investigate this island evolution using high-resolution satellite datasets with geodetic-quality ICESat-2 altimetry. Lansdat-8 and Planet imagery provide a qualitative analysis of the exposed volcanic deposits, while ICESat-2 products provide elevation profiles necessary to quantify the physical surface structures. This investigation determines an innovative application for ICESat-2 data in evaluating newly emerged islands and how the combination of satellite remote sensing (visible and lidar) to investigate these short-lived volcanic features can improve our understanding of the volcanic island system in ways not previously possible.
Highlights
Submarine volcanism presents as underwater fissures built from the seafloor volcano-tectonic structure and tend to be more difficult to monitor quantitatively because of the remote locations and the absence of easy observational access
Since submarine volcanism occurs predominately in more remote oceanic locations, in situ and continuous measurements are limited, which elevates the need for using the space-based vantage point to monitor the dynamics associated with these events
This effort establishes one specific combinations of instrument observations to quantify the development and erosion of volcanic systems, such as Niijima FukutokuOkanoba (NFO), via some of the most recent onreturns within the shallow water zone on both sides of the island in Figure 5i,j shows, roughly, a three times greater return in the southern side, reinforcing the hypothesis of increased turbidity in this area. Further investigation of this theory may establish a quantitative method using the ATLAS radiometric response to evaluate shallow water erosion. This rapid response technique using both satellite laser altimetry and visible satellite imagery provides a novel method for evaluating emerging volcanic structures
Summary
Submarine volcanism presents as underwater fissures (and vents) built from the seafloor volcano-tectonic structure and tend to be more difficult to monitor quantitatively because of the remote locations and the absence of easy observational access (see [1,2]). Satellite imagery can be used to visibly identify volcanic submarine eruption events in shallow waters predominantly based on the distinct discoloration in the water column [2], but is limited in specific 2D eruption characterizations This visible coloration change from milky white to a reddish-brown is often caused by very fine materials (tephra) produced from the interaction of the surrounding seawater with the super-heated water from the underwater erupting volcano [4]. These volcanic structures provide an opportunity to investigate the early evolutionary stages of volcanic island systems, additional monitoring techniques need to be developed via newly available remote sensing data streams such as satellite laser altimetry (among others)
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