USGS Preliminary Analysis_LERZ_7-15-18_v1.1

Home

COOPERATOR REPORT TO HAWAII COUNTY CIVIL DEFENSE Preliminary Analysis of the ongoing Lower East Rift Zone (LERZ) eruption of Kilauea Volcano: Fissure 8 Prognosis and Ongoing Hazards Prepared by the U.S. Geological Survey Hawaiian Volcano Observatory July 15, 2018 (V 1.1) Introduction In late April 2018, the long-lived Pu'u 'O'o vent collapsed, setting off a chain of events that would result in a vigorous eruption in the lower East Rift Zone of Kilauea Volcano, as well as the draining of the summit lava lake and magmatic system and the subsequent collapse of much of the floor of the Kilauea caldera. Both events originated in Lava Flow Hazard Zone (LFHZ) 1 (Wright et al, 1992), which encompasses the part of the volcano that is most frequently affected by volcanic activity. We examine here the possible and potential impacts of the ongoing eruptive activity in the lower East Rift Zone (LERZ) of Kilauea Volcano, and specifically that from fissure 8 (fig. 1). Fissure 8 has been the dominant lava producer during the 2018 LERZ eruption, which began on May 3, 2018, in Leilani Estates, following intrusion of magma from the middle and upper East Rift Zone, as well as the volcano's summit, into the LERZ. The onset of downrift intrusion was accompanied by collapse of the Pu'u 'O'o vent, which started on April 30 and lasted several days. Kilauea Volcano's shallow summit magma reservoir began deflating on about May 2, illustrating the magmatic connection between the LERZ and the summit. Early LERZ fissures erupted cooler lava that had likely been stored within the East Rift Zone, but was pushed out in front of hotter magma arriving from farther uprift. This hotter magma, similar in composition to lava that had been erupting at Pu'u 'O'o, arrived in mid-May, coincident with an increase in discharge from the fissures. The volume of lava erupted during the current activity exceeds that of many past eruptions. Given this volume and the sustained withdrawal of magma from the summit reservoir without appreciable deformation in the lower East Rift Zone, it is most likely that the LERZ eruption may continue for months to years. While additional fissures may form either uprift or downrift of the current activity, the continued focus of activity within the current fissure system after 10 weeks of activity (as of July 15, 2018) makes this scenario increasingly unlikely. This document reviews current activity, focusing on the fissure 8 vent, channel, and ocean entry. It describes a credible set of future scenarios for fissure 8 and discusses uncertainties. This document is meant as a guide for managing hazards and risks in Kilauea's East Rift Zone.