Graph showing the depth of the Halema‘uma‘u crater lava lake at Kīlauea Volcano's summit. Measurements began one day after the start of the eruption on December 20, 2020 and are updated by geologists making observations from the field. HVO field crews use a portable laser range finder to measure the vertical distance between points of known elevation and the lava lake surface. Frequent sets of repeat manual measurements were averaged and plotted to derive the lava lake depth.  

On January 8, 2021, a novel laser rangefinder was stationed at Kīlauea Volcano's summit. The fixed instrument continuously measures the distance to the lava lake surface, and telemeters data to HVO in real time. The raw data has been edited for this graph, with a running mean average filter of 3600 seconds. 

Variations in plotted depth can occur due to alternating field crews, the uneven surface of the lava lake, or laser rangefinder returns on gas rather than the lake surface.

Sulfur dioxide (SO₂) emission rates measured using an upward-looking ultraviolet spectrometer. These data are collected by traversing the gas plume in a vehicle or helicopter, downwind of Halema‘uma‘u, generally within and/or southwest of Kīlauea caldera. Results from multiple traverses during a day are averaged to yield the emission rates shown here. Successful measurements depend on wind, weather, and staff availability. Values are preliminary and are subject to revision.

This map of Halema‘uma‘u at the summit of Kīlauea shows 20 m (66 ft) contour lines (dark gray) that mark locations of equal elevation above sea level (asl). The map shows that the lava lake has filled 224 m (735 ft) of the crater, to an elevation of 741 m (2431 ft) asl since the eruption began on December 20, 2020. Contour lines highlighted in green, purple, and blue mark the approximate rim of Halema‘uma‘u, the edge of the eastern down-dropped block, and the approximate rim of the 2018 collapse, respectively. Lava is expected to be within view of the Kīlauea Overlook visitor area shortly before it rises to the level of the green contour line at 800 m (2625 ft) asl. USGS map.