Bathymetry of Eruptive Fissures in the Submarine North Arch Volcanic Field

Abstract

Submarine volcanoes make up 75% of volcanic activity on Earth, but are relatively understudied due to the lack of real-time observations of eruptions and their inaccessibility, often several kilometers below sea level. Underwater volcanoes behave differently than their land counterparts due to the cold sea water surrounding them. Some submarine volcanism is violent as water pours into active vents, rapidly cooling lava and shattering it into fragments. Other eruptions can produce lava flows that extend tens of several kilometers before solidifying. The majority of submarine volcanoes occur in areas of tectonic activity such as mid-ocean ridges and hotspot island chains. One interesting site of submarine volcanic activity is the Submarine North Arch Volcanic Field 100 kilometers north of Oahu, Hawaii, hosting a few of the longest flows on Earth and covering over 25,000 kilometers2. The field is associated with the Hawaii hotspots but the source of such extensive volcanism is poorly understood. Past studies have mapped the volcanic field flow but only at low resolution. The southeast portion of the field comprises of a series of lengthy flows, hypothesized to emanate from a 75 kilometer long fissure in the seafloor. However, the resolution of the maps was too low to test this theory. On the R.V. Thomas G. Thompson, our team used the high-resolution Kongsberg EM302 30-kHz multibeam echosounder to map the eastern boundary of the southeastern lava flow where the fissure would likely be located. Although area covered was limited by bad weather, we were able to map a 6 kilometer wide swath track extending 63 kilometers along the inferred fissure. We identified the presence of three features that were potentially part of fissures. Each extends about 1-2 kilometers and comprise a 5 meter deep and 100-400 meters wide trough with a levee on either sides.