The 1996 Eruption at Loihi Volcano

The 1996 Eruption and July-August Seismic Event

This document contains an Introduction to the 1996 Eruption of Loihi
MOST RECENT ACTIVITY IS SUMMARIZED ON THE LOIHI UPDATE PAGE

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THE 1996 ERUPTION - WHAT HAPPENED? The largest swarm of earthquakes ever recorded on ANY Hawaiian volcano lasted for 2 months of summer 1996 at Loihi seamount (see graphic below). It began on 17 July 1996 and by the end of August, a total of over 4000 earthquakes have been recorded by the Hawaii Volcano Observatory (HVO) network, with more than 40 earthquakes between magnitude 4 and 5 recorded by the World Wide seismic network.

In August 1996, a National Science Foundation-funded expedition to Loihi by UH scientists began investigating this unique event and its origin. Additional "follow-up" expeditions to Loihi (including a series of manned-submersible dives completed in August and September of 1997) as well as a great deal of shore-based research have been conducted since then. Ongoing results are described on the Loihi Update Page

SUMMARY OF THE 1996 ERUPTION AND SEISMIC EVENT (Compiled from the research of many individuals)

There was at least one, possibly two eruptions at Loihi in 1996, based on radiometric dating of young lavas collected by manned-submersible from Loihi
The summit of Loihi has undergone some drastic changes in 1996, including the formation of a third new pit crater and deposition of large quantities of glassy sands and gravels on the southern part of the summit platform
New vents issuing the hottest waters ever observed at Loihi (up to 200 ° C) are present in the new pit crater
The water column above Loihi has signatures of enhanced hydrothermal activity at or near the summit

Events with known dates are summarized in the image below (by Ken Rubin of the Univ. of Hawaii). Included are the seismic swarm (shown as a histogram of events in orange), the date of the initial Rapid Response Expedition to Loihi in August of 1996, and the ²¹⁰Po-²¹⁰Pb "eruption windows" (in red) of allowed eruption dates for two samples collected in August 1996 from the Loihi summit. The small pink bars represent uncertainty in the maximum age of lavas and the light purple t-bars ( ---| ) depicts the date of sample collection. Also shown is the calendar year 1997 running across the bottom of the figure. The info in this figure, as well as results of other petrological and geochemical research on lavas from this eruption are to described in this recently published paper by UH scientists and their colleagues from other institutions:

Bull. Volcanol.

The histogram below of depicts seismic events during the "swarm". Each red vertical bar represents a 6-hour time interval; the green swath represents the time period during which the UH R/V KOK event response cruise was at the seamount. (This figure contains unpublished but copyright protected data. Use by permission of the webmaster only)

Earthquakes of the seismic swarm at Loihi are depicted in the two diagrams below (by Jackie Caplan-Auerbach at the UH; These figures contain unpublished but copyright protected data. Use by permission of the webmaster only).
	On the left, earthquakes from the recent swarm have been superimposed on a bathymetric map of the seamount Click on either of these image to view them full-scale.
	In this second image, the locations of recent Hawaiian Earthquakes between 1 July and 22 Sept. 1996 (including those at Loihi) are superimposed on a map of the Big Island of Hawaii. Earthquakes are color-coded by date of occurence (red = 1-19 July 1996, green = 19-31 July 1996, yellow = 1 Aug-22 Sept 1996).

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Last page update on 22 Jul 1998