USGS Drone, Second Batch Of Water Samples From Kilauea

Imagery and text from USGS-HVO Field observations today show that the diameters of the crater lake within Halema‘uma‘u at the summit of Kīlauea are about 94 m (308 ft) north-south and around 192-195 m (630-640 ft) east-west. Too much steam at the west end interfered with measurements this morning. Two small circles above the northeast edge of the water show how much the lake has grown since January 24. On January 17, 2020, USGS-HVO scientists and DOI Unoccupied Aerial System (UAS) team members collected three additional samples of water from the Halema‘uma‘u crater lake. Here, the sampling device and temperature logger were readied for takeoff. The plastic sleeve was attached to the UAS (drone) with a cord about 20 feet (6 m) long. Colored flags were attached to the cord at 5-foot (1.5-m) intervals so that the UAS pilot and other team members could visually gauge how deep the sampler was under the water surface. One water sample was collected close to the lake surface. Two others were collected from a depth of 10-15 feet (3-4.5 m)—one in a yellow-orange patch of water and the other in a yellow-green patch of water. The purpose of the UAS flights was to collect water samples and gas data to assess ongoing volcanic hazards. HVO's work in a culturally sensitive area closed to the general public was done with permission of Hawai‘i Volcanoes National Park. After a sample was collected, HVO team members transferred water from the sampling device to plastic bottles. The scientists wore protective gear, including hardhats in case of rockfall hazards near the crater rim, as well as aprons, goggles, and gloves to shield them from the hot, acidic water. Team members took notes, measured water pH, and evaluated water temperature data for each sample collected. Water temperatures up to 60 degrees Celsius (140 degrees Fahrenheit) were recorded but are an underestimate due to equilibration time issues with the temperature sensor. Remote measurements of the water's surface temperature via a thermal camera have consistently indicated temperatures of 70-80 degrees Celsius (roughly 160-175 degrees Fahrenheit). Field measurements of pH indicated values of 4.3 for the surface water, 4.2 for the yellow-orange water, and 3.9 for the yellow-green water (pH of the October 26, 2019, sample was 4.2). Additional laboratory analyses by USGS California Volcano Observatory colleagues revealed that the three January samples, while more dilute (perhaps due to recent heavy rainfall), are chemically similar to the water sampled in October, which indicates ongoing reactions between the lake water, volcanic gases, and the surrounding basaltic rocks. HVO's work in a culturally sensitive area closed to the general public is done with permission of Hawai‘i Volcanoes National Park. The purpose of the UAS flights was to collect water samples and gas data to assess ongoing volcanic hazards.