Report on Loihi (United States) — October 1993
Bulletin of the Global Volcanism Network, vol. 18, no. 10 (October 1993)
Managing Editor: Edward Venzke.
Loihi (United States) Seismic swarm on S flank
Please cite this report as:
Global Volcanism Program, 1993. Report on Loihi (United States) (Venzke, E., ed.). Bulletin of the Global Volcanism Network, 18:10. Smithsonian Institution.
18.92°N, 155.27°W; summit elev. -975 m
All times are local (unless otherwise noted)
A microearthquake swarm occurred on the morning of 12 October 1993 with >140 events counted in two days. The peak of this activity occurred in the first 4 hours with 90 events counted from 1000-1400 on 12 October. Eight of these events had M >3. Hypocentral determinations indicated that the S flank of the seamount was active at that time.
Geologic Background. Loihi seamount, the youngest volcano of the Hawaiian chain, lies about 35 km off the SE coast of the island of Hawaii. Loihi (which is the Hawaiian word for "long") has an elongated morphology dominated by two curving rift zones extending north and south of the summit. The summit region contains a caldera about 3 x 4 km wide and is dotted with numerous lava cones, the highest of which is about 975 m below the sea surface. The summit platform includes two well-defined pit craters, sediment-free glassy lava, and low-temperature hydrothermal venting. An arcuate chain of small cones on the western edge of the summit extends north and south of the pit craters and merges into the crests prominent rift zones. Deep and shallow seismicity indicate a magmatic plumbing system distinct from that of Kilauea. During 1996 a new pit crater was formed at the summit, and lava flows were erupted. Continued volcanism is expected to eventually build a new island; time estimates for the summit to reach the sea surface range from roughly 10,000 to 100,000 years.
Information Contacts: T. Mattox and P. Okubo, USGS Hawaiian Volcano Observatory.