Volcano Watch — Same rift zone eruption continues

The eruption along Kīlauea's East Rift Zone continues with little change since our last report in mid-June. There are still two erupting vents located on the southwest and west flanks of the Pu'u 'O'o cone, which is located about 11 miles east of Kīlauea's summit. The lava from these two vents directly enters underground tubes that transport it to the coast at Lae Apuki at the end of Chain of Craters Road inside Hawaii Volcanoes National Park.

The tube system has changed little in the last six weeks, with the exception of several breakouts that fed small surface flows. These breakouts have occurred several weeks ago and again on Wednesday and Thursday of this past week. In each case, the lava breached the tube system where the tube comes over Paliuli, a 50-foot-tall fault scarp located about one-half mile from the coast.

We continue to monitor the lava supply rates using a geoelectrical technique which can measure the cross-sectional area of the lava stream inside the tube. The technique works on the simple principal that the liquid lava is an electrical conductor, whereas the solid lava is a resistor. By multiplying the cross-sectional area by the measured flow rate, we can estimate the volume of lava per unit time. Starting last February, the measured rates averaged about 500,000 cubic meters per day but varied from about 600,000 cubic meters per day to as little as 300,000 cubic meters per day. During the last two weeks, the flux has been highly variable, at one time varying between the minimum and the maximum noted above in a matter of a few hours. Our most recent measurements, taken this past Thursday, indicate that the flux has decreased and is now roughly 250,000 cubic meters per day.

This past week has seen some exciting activity where the lava enters the ocean at Lae Apuki. Starting Wednesday morning, a secondary cone has formed where the well-consolidated lava channel entered the ocean. Such cones form from spatter, ribbons of molten lava, and tephra that are explosively thrown into the air and pile up around a hole in the tube system. The explosions are steam-driven and result from heating of seawater that has entered the lava tube. The last time we saw such explosive activity was in March. By Friday morning, the activity had built a cone about 100 feet in diameter and about 50 feet tall. The activity pulsed, such that there were periods of nearly continuous fountaining and explosions and periods of inactivity. The most intense activity took place on Wednesday and continued into Thursday. On Wednesday evening, nearly continuous explosions ended about one hour after a surface flow broke out on Paliuli. By Friday morning, the coastal area was quiet once again.

Shoreline Hazard

Last weekend, a person was scalded by near-boiling seawater after going beyond area closure signs that warn of dangers near the coast where lava enters the ocean. National Park Service Rangers issue citations to people found within the closed areas. More importantly, the area closure signs are posted to protect you from episodic hazards that can occur with little or no warning. These hazards include collapse of sections of the lava ledge along the ocean, acidic fumes, larger than average waves that can scald you, because the seawater is heated by lava, and unexpectedly large explosions that can hurl molten lava and solid incandecent blocks far inland. In addition, we recently mapped a block deposit along the coast and realized that it was emplaced by a large wave, probably a small tsunami, that was generated when a lava bench collapsed into the ocean. The blocks are located several hundred feet inland from the coastal lava ledge. Enjoy the activity from a safe distance and obey all posted warning and closure signs.