Lake atop Hawaiian volcano is mysteriously changing color ‘by the minute.’ But why?

A lake that started mysteriously growing atop Hawaii’s Kilauea volcano is puzzling scientists yet again, by exhibiting rapidly changing “dynamic colors and patterns” ... and even signs of movement.

The Halemaumau crater lake, which began forming 16 months ago, is one of the world’s deadliest bodies of water: 154 feet deep and a skin-scalding 185 degrees.

Yet it is proving to be anything but stagnant, leaving the U.S. Geological Survey scrambling to understand what’s going on beneath it.

“The water surface is a mosaic in constant motion, a scene that changes by the minute and hour. Sharply defined color boundaries are often seen,” the USGS wrote in a Nov. 6 Facebook post.

“When it first emerged, it was described as a pond of milky turquoise water. Later, it developed yellow hues and green shoreline margins. Today, the lake surface has lobes of rust orange water over expanses of deep brown ... Elongated green inflows emerge from the rocky shoreline, along which several ruddy spots have recently upwelled.”

The “patchwork” of colors could be due to minerals melting in “distinct temperature” zones, experts say. And the movement could be attributed to the water density, winds and rising groundwater, the USGS wrote.

However, what’s alarming is anecdotal evidence that certain color changes may precede eruptions. An example happened in 2003, when a lake at Japan’s Aso Volcano “changed from blue green to solid green before an eruption,” the USGS says.

The Hawaiian Volcano Observatory says it recently began collecting color data from the lake, using a colorimeter instrument “more commonly used in industries like food processing and textile manufacturing.” The instrument measures depths of “wavelength and intensity of light” not visible to the naked eye, officials said.

“Analysis of the colorimetry data from this experimental technique may help scientists explain the dynamic colors,” the USGS said. “While we don’t know if the water lake within Halemaumau would have a similar color change (to Aso Volcano) prior to an eruption, it is a potential indicator.”

Experts remain unsure as to what is causing the lake to stay so hot. It could be due to “residual heat ... from rock that was heated by the lava,” according to an August USGS report. It might also be connected to nearby gas vents (fumaroles) that generate heat of around 300 degrees, the report said.

The lake appeared after a May 2018 eruption that caused the floor of Kilauea’s caldera to collapse, creating “a hole nearly as deep as One World Trade Center,” NASA’s Earth Observatory reported. “The water table in this area is estimated to be 230 ft above the crater floor, so the lake level will slowly continue to rise until it equilibrates with the local water table,” the USGS says.

It is a source of concern because “magma interacting with near-surface water can, in some circumstances, trigger steam-blast explosions,” the USGS reports.

This story was originally published November 9, 2020 at 12:04 PM with the headline "Lake atop Hawaiian volcano is mysteriously changing color ‘by the minute.’ But why?."