Volcano Watch: Innovative monitoring of Kilauea’s summit water lake

  • M. PATRICK/USGS photo The colorful caldera lake at Kilauea summit on Aug. 25. The view is from the western rim of Halema‘uma‘u crater, 1,900 ft (580 m) above the water surface, in a restricted area of Hawaii Volcanoes National Park.

  • M. PATRICK/USGS photo A Hawaiian Volcano Observatory scientist tests a colorimeter instrument on the water lake within Halema‘uma‘u at Kilauea’s summit. Colorimetry is the measurement of the wavelength and intensity of light.

Famous for glowing red lava and billowing volcanic plumes, Halema‘uma‘u has long inspired poets, painters and photographers to find meaning in the color and light of this dynamic landscape.

Today, Kilauea’s current phase of activity has inspired volcanologists to experiment with cutting-edge techniques to understand the dynamic colors and patterns of Halema‘uma‘u’s newest feature: a steaming hot water lake.

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For 15 months, hot groundwater has been seeping into the collapse pit created by the evacuation of the 2008-18 Halema‘uma‘u lava lake and part of the underlying summit magma chamber. Since the gaping pit and the water lake rising within are physically inaccessible, the USGS Hawaiian Volcano Observatory uses remote techniques to monitor this changing, and potentially hazardous, environment.

HVO uses unoccupied aircraft systems (UAS, or “drones”) to collect water samples, the chemical analyses of which are snapshots of lake composition. Visual and thermal cameras keep constant watch on the lake surface and the hot fumaroles surrounding it. LiDAR (Light detection and ranging) helps to reveal the lake’s growing form. A digital elevation model (DEM) is integrated with frequent water level measurements to calculate lake depth, volume and inflow rate. These quantitative data sets are complemented by the written accounts of HVO scientists, who document their firsthand observations in field logs.

The lake gives strong impressions of color, pattern and motion. 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, with patches of light brown and tan. Elongated green inflows emerge from the rocky shoreline, along which several ruddy spots have recently upwelled.

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, accompanied by more subtle gradients and mixing. The patchwork waters might indicate zones of distinct temperature and dissolved constituents, and their movement is likely driven by differentials of density, wind and fresh groundwater inflow.

As HVO scientists documented the lake’s early growth and development, they recognized the need to define these valuable visual observations of color with quantitative measurements, and to help control for variable effects of lighting, personal impressions and the color biases in cameras.

A colorimeter instrument, a handheld optical device that measures chromaticity and brightness, is being field tested for this purpose. A similar type of color measurement was conducted at Aso Volcano in Japan in 2010, inspiring the techniques used by HVO. In an experiment to test its efficacy at Kilauea, HVO scientists use a portable colorimeter to quantify visual observations and track color changes through time.

Colorimeters are commonly used in industries such as food processing and textile manufacturing. Colorimetry is the measurement of the wavelength and intensity of light. The quantification of color can be divided in two parts. Brightness, or luminicity, is the quantity of light reflected, emitted from or that passes through an object. Chromaticity is a measurement of hue and colorfulness, independent of brightness. Colorimetry relates these variables to the human eye’s sensation of color, and to our judgment of the physical stimulus of light.

In the field, scientists make broad visual observations, then sight the colorimeter at a point of interest. The record of chromaticity and brightness builds upon hydrologic and geologic data sets, contributing insight that might help link other remote observations. Analysis of the colorimetry data from this experimental technique might help scientists explain the dynamic colors seen at the Halema‘uma‘u lake.

Lake color changes might possibly even signal changing volcanic conditions beneath the watery depths. Water color and appearance changes have been observed at other active crater lakes around the world. For example, at Aso Volcano in Japan in 2003, Yudamari lake changed from blue-green to solid green before an eruption occurred at the lake bottom.

While we don’t know if the water lake within Halema‘uma‘u would have a similar color change prior to an eruption, it is a potential indicator HVO scientists will be looking for and tracking as part of routine monitoring in the post-2018 collapse era of Kilauea activity.

Volcano activity updates

Kilauea Volcano is not erupting. Its USGS Volcano Alert level remains at Normal (www.usgs.gov/natural-hazards/volcano-hazards/about-alert-levels). Kilauea updates are issued monthly.

Kilauea monitoring data for the month of October show variable but typical rates of seismicity and ground deformation, low rates of sulfur dioxide emissions and only minor geologic changes since the end of eruptive activity in September 2018. The water lake at the bottom of Halema‘uma‘u continues to slowly expand and deepen. For the most current information about the lake, visit www.usgs.gov/volcanoes/kilauea/k-lauea-summit-water-resources.

Mauna Loa is not erupting and remains at Volcano Alert Level Advisory. This alert level does not mean an eruption is imminent or progression to eruption is certain. Mauna Loa updates are issued weekly.

This past week, about 42 small-magnitude earthquakes were recorded beneath the upper-elevations of Mauna Loa; most of these occurred at shallow depths of less than 8 kilometers (about 5 miles). GPS measurements show long-term, slowly increasing summit inflation, consistent with magma supply to the volcano’s shallow storage system. Gas concentrations and fumarole temperatures as measured at Sulphur Cone and the summit remain stable. Webcams show no changes to the landscape. For more information about current monitoring of Mauna Loa Volcano, visit www.usgs.gov/volcanoes/mauna-loa/monitoring.

There were three events with three or more felt reports in the Hawaiian Islands during the past week: a M2.6 earthquake 6 km (3 mi) N of Waiohinu at 0 km (0 mi) depth at 6:40 a.m. Nov. 3, a M3.5 earthquake 9 km (5 mi) ENE of Pahala at 30 km (18 mi) depth at 1:47 a.m. Nov. 2 and a M2.9 earthquake 1 km (0 mi) W of Pahala at 34 km (21 mi) depth at 8:25 a.m. Oct. 31.

HVO continues to closely monitor Kilauea and Mauna Loa for any signs of increased activity.

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Visit HVO’s website for past Volcano Watch articles, Kilauea and Mauna Loa updates, volcano photos, maps, recent earthquake info and more. Email questions to askHVO@usgs.gov.

Volcano Watch is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates.

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