July 21, 1995

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.

Hualalai

For several weeks we have been fielding calls from anxious people in Kona asking about an imminent eruption of Hualalai Volcano. Our seismic monitoring of Hualalai indicates no increase in earthquake activity, and recent geophysical measurements show no change in the regional gravity field. These data suggest that there is no movement of magma within Hualalai. Our annual geodetic measurement of Hualalai will be done later this month, and we do not anticipate any significant surface deformation changes. Hualalai is not showing any signs of reawakening at this time.

As most people are aware, Hualalai is one of three volcanoes classified as active on the island of Hawai`i. To be classified as active, a volcano has to have erupted in historic time. The last eruptions of Hualalai were in 1800 and 1801. The Ka`upulehu and Hu`ehu`e flows are the products of those eruptions which issued from the northwest rift zone of the volcano.

Hualalai has three rift zones. One strikes north from the summit to Pu`u Wa`awa`a, another is toward the south-southeast to Pu`u Lehua, and the third, outlined by cinder cones, extends from the summit, northwest to Makalawena, and continues for another 40 miles offshore. Eruptions may occur from vents along any of these rift zones or from the summit area.

The last crisis at Hualalai was in 1929, when a swarm of earthquakes rocked the region from September 19 to mid-December. Two of the temblors were large enough to be felt on `Oahu. From the temporal pattern of energy release, the earthquakes were probably related to magmatic intrusion and not tectonics. A similar swarm of earthquakes should precede the next eruption of Hualalai and provide us with ample time to act.

Kilauea Volcano continues to erupt, and the lava flow activity has not changed significantly since our last report. Lava keeps moving from the vent to the ocean in a well-established tube system with occasional minor surface breakouts. The main ocean entry is located near the High Castle overlook area, and visitors can view this spectacular action from safe observation sites near the end of the Chain of Craters Road. Visitors are reminded to heed the safety warnings of the National Park Service and not risk their lives by going into restricted areas that are highly dangerous.

The U.S. Geological Survey's Hawaiian Volcano Observatory will have a display on the seismic hazards of Hawaii and ways to mitigate the hazards at the Hawaii Contractors' Association's Building Exposition to be held this Friday and Saturday at the Afook-Chinen Civic auditorium. The public is welcome to come and enjoy the numerous and varied displays and to meet our staff members.