By PETER SUR
Tribune-Herald staff writer
When Pele speaks, people listen.
For the last few nights, visitors to the Thomas A. Jaggar Museum overlook at the summit of Kilauea have been hearing constant “booming and popping sounds” from the glowing lava lake.
The causes of the sounds are no mystery. The lava lake, now 525 feet across, has recently reached an all-time high of 157 feet below the floor of Halema‘uma‘u crater.
The lake is heating and weakening the vent’s rock walls, causing pieces of the vertical conduit to fall in.
“Of late people are hearing a lot of sounds from Halema‘uma‘u,” said Janet Babb, a geologist with the U.S. Geological Survey Hawaiian Volcano Observatory, which is located adjacent to Jaggar Museum. “Because of the high level of the lava lake the rocks in the wall of the vent rim above the lava level are being heated, and as they heat they expand. That causes them to crack.”
It’s a continuous sound; one person described it as “heavy rain falling on the surface of the lava pond.”
“There’s a lot of booming and popping sounds that can be heard from the Jaggar Museum overlook,” Babb said.
The recent lack of trade winds is making the sound audible over longer distances, Babb said, so the expected return of normal weather patterns could diminish it.
The volcano has done this before. In late February 2011, following an extended period of inflation, the lava lake reached a high level and the walls of the vent began to crack, causing booming sounds that were audible from the Jaggar overlook.
By March 3, 2011, the walls of the vent had weakened so much that large sections of the rim began to fall into the lava lake, creating large clouds of dust. Three days later, the underground conduit carrying magma to Pu‘u ‘O‘o ruptured and the short-lived vent known as Kamoamoa erupted lava on the East Rift Zone.
This time, geologists have not seen the seismic signals that would indicate an imminent flank eruption, but they are watching Kilauea’s magma reservoir repressurize. Tuesday marked the ninth straight day of inflation.
Babb said the prolonged period of inflation is “worth noting, but not extraordinary.”
What happens next will depend on a number of factors. The lava supply could decline, ending the inflationary trend of the last nine days and causing the surface of the lava lake to recede. The magma conduit could rupture anywhere between Halema‘uma‘u and Pu‘u ‘O‘o, as it did in the Kamoamoa fissure eruption of 2011. Or, if the lava lake keeps rising, it is possible that lava could spill out of the vent and onto the crater floor.
According to HVO’s Tim Orr, the lava lake still has a ways to go before visitors to the Jaggar Museum overlook can view it directly. Orr calculated that the lake won’t be visible unless it rises to within 65 to 80 feet of the crater floor. Until then, visitors will have to be content with the glow.
But geologists are noticing that while the level of the lava lake rises and falls daily (it was 167 feet below the crater floor on Tuesday), over time it has been rising higher.
In March 2011, the lake was 230 feet below Halema‘uma‘u’s floor.
Then the Kamoamoa eruption drained the lava lake, creating a gaping, fuming cavern perhaps 660 feet deep. The lake has refilled slowly, in fits and starts, over the last year and a half.
Lava from the lake returns underground as magma and appears at Pu‘u ‘O‘o, where it enters a series of lava tubes on its way through Royal Gardens and on the coastal plain to the sea.
Surface flows remain active in Kalapana, but webcams show that the lava is still advancing across the plain, about a mile from the ocean.
Email Peter Sur at firstname.lastname@example.org.