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Kīlauea Eruption Update: Lava Lake Shrinks Almost 25% In Past Week

7:21 PM · Apr 27, 2021

According to our estimates based on USGS photos, time-lapse sequences, and map area calculations, Kīlauea’s open lava lake surface has shrunk by close to 25% over the past week. Meanwhile, gas emissions have decreased by about half since last week, all while low lava output continues. There is still liquid lava below the newly crusted areas on the northeast and southwest lake margins, but it loses some volume as it cools, degasses and compresses, according to USGS-HVO. As a result, the recently stagnant surface now sits 7-10 ft (2-3 m) lower than the active lava surface nearby, which itself has slowed its rise to only ~1.6 ft (~0.5 m) during the past week, only to regain its previous depth of 227 m (745 ft). Latest on Kīlauea, Eruption Day 128, Week 18: -Active lake surface shrinking continues at the time of this writing; our estimates yield reductions of ~20% in the southwest and ~5% in the northeast, thus far. -Another Deflation-Inflation cycle begins today, after completing the third leg of a triple DI over the first half of the week. Possibly related, no ooze-up flows have been observed along the lake’s perimeter, next to the crater walls, during the past 2 weeks. -SO2 measurements from April 21-25: 350 tonnes/day, 550 t/d, 300 t/d, 350 t/d, 375 t/d (USGS), “among the lowest emission rates measured during the current eruption.” The single measurement during the previous week was 950 t/d on April 14, while the previous low measurements ranged around 500-600 t/d about one month ago, at the end of March. -GPS shows continued caldera spreading, with a possible increase in the extension rate following the slow-down over the past month. Seismic activity is still within background levels, and still focused mainly below the summit and South Flank. Join our weekly live video review of Kīlauea’s eruption! Broadcast at 5pm HST Tuesdays and archived, along with short video updates, on this channel - including monitoring signals, photos & videos, time-lapses, geologic context and annotation, and discussion of live viewer questions. #Kilauea2021 Image 1: This zoomed-in photo of the far southwest end of the active lava lake within Halema‘uma‘u at Kīlauea's summit was captured on Thursday, April 22, and it illustrates the process by which parts of the lava lake become inactive. This area, which had seen substantial lava circulation as recently as last week, now has a stagnant pāhoehoe crust that sits 2–3 m (7–10 ft) lower than the fluid lava surface just to the northeast (right). This crust overlies and possibly overhangs fluid lava underneath, as evidenced by the incandescence visible through a hole along the levee at left. The process starts when the circulation of surficial lava slows in a part of the lake—for reasons that are not entirely clear—allowing the pāhoehoe crust to form. At this point, the area is no longer replenished with new surface lava, and the underlying molten lava will actually contract due to degassing, compression, and cooling. The crust may remain attached to the levees, and as the lava underneath cools and contracts, voids can form below the crust. Eventually, deeper accumulation of molten lava may start lifting this area again, as has happened in the eastern end of the Halema‘uma‘u lava lake. USGS image & caption. Image 2: On Thursday, April 22, HVO scientists observed the ongoing eruption at the Kīlauea summit from the south rim of Halema‘uma‘u. This photo shows the active western portion of the lava lake, which appears to be in the process of shrinking again, with its northeast (upper-right) and southwest (lower-left) ends crusting over substantially. For scale, the distance from the western fissure (upper-left) to the nearest part of the main island in the lake (lower-right) is approximately 180 m or 590 ft. USGS image & caption.