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Geologists sample growing pond in Halema‘uma‘u

U.S. Geological Survey’s Hawaiian Volcano Observatory on Saturday collected samples from the growing water pond in Kilauea volcano’s Halema‘uma‘u crater.

HVO confirmed the presence of water in the bottom of Halema‘uma‘u this summer.

Patricia Nadeau, a research geologist with HVO, said there has always been ground water near the Kilauea summit.

HVO can measure the height of groundwater in the summit area using a well located about a kilometer south. But the ground was too high and lava present at the summit kept the ground too warm, so “water was never able to make it to the surface,” she said.

The volcano’s 2018 eruption, however, led to the collapse of the summit area.

“Now we have this deeper crater bottom that is lower than where we knew the ground water level to be based on the well,” Nadeau said.

One of the reasons HVO wanted to collect a sample from the pond was to test the water’s chemistry to confirm whether it’s rainwater, “which we don’t think it is,” or groundwater, she said.

“It also gives us an indication of how much the water is interacting with the volcanic gases coming from the deeper magma,” Nadeau said.

Sulfur dioxide emissions “are a proxy for volcanic activity,” she said.

Last year, there were “huge amounts of that coming out, and now we have very little we’re able to measure, but one of the issues is that sulfur dioxide is very easily dissolved in water,” Nadeau said. “So now that we know we have water, it’s likely at least in part we’re getting low emission rates of sulfur dioxide because it’s getting dissolved in the water.”

Nadeau said other volcanic observatories around the world with crater lakes like the one in Halema‘uma‘u monitor water chemistry changes through time to see if any differences coincide with changes in volcanic activity.

HVO, however, doesn’t have any such plans in place yet, she said. They were “happy to get the first sample.”

According to Nadeau, an unmanned aerial system flown by USGS colleagues from the mainland was used to collect the sample. She said this is the first sample of water that has been collected.

The sample was sent to the California Volcano Observatory for chemical analyses.

According to the HVO website, water levels at the summit continue to slowly rise, and the pond is gradually enlarging. As of Friday, the pond was at least 460 feet long in the east-west direction.

According to Nadeau, the lake is located about 656 yards below the crater rim.

HVO scientists are “still learning” about the lake, and Nadeau said they monitor the water by also visually looking for color changes or measuring surface temperatures.

Current surface temperatures are about 158 degrees.

Halema‘uma‘u has never had a pond of water since written observations began, HVO said in a “Volcano Watch” article in August.

Email Stephanie Salmons at ssalmons@hawaiitribune-herald.com.
Source: Hawaii Tribune Herald

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