Evening Kīlauea Eruption Update, Dec 27 - Eruptive Vigor Declines

(Dane Dupont, Ryan Finlay) Tonight marks one week since the eruption began and there is the possibly of surface activity pausing or becoming intermittent in the days ahead. USGS releases map comparing the size of the lava lake currently to the lava lake from prior to the 2018 eruption. First, gas emissions have dropped by a factor of 8 since the height of the eruption earlier this week. Reducing from ~40,000 tonnes per day on December 21-23, down to ~20,000 tonnes on Christmas night, and dropping further to 5,000 tonnes per day in the last measurement taken by USGS. For context, the SO2 emissions today are closer to the long term average from the 2009-2017 lava lake in Halema’uma’u, roughly at 5,000-6,000 t/d, after averaging out the short term variance. During the height of the 2018 eruption at Fissure 8, in June, the SO2 emissions reached roughly 200,000 t/d. [1] In general, sulfur dioxide emissions are often connected with eruption effusion rates. The effusion rates also seem to have dropped in the last few days alongside SO2 emissions. Earlier this week, the northern vent and primary eruptive vent were submerged in lava after the depth of the lake surpassed the elevation of the eruptive vent. Shortly afterwards, activity transferred over to the more elevated western vent, which reactivated with vigor for a few hours before slowing to a more stable level, but at a level less than was seen at the northern vent. Lava from the lake preceded to backflow into the inactive northern vent as pressure fell, and fed back into the shallow magma system the summit began to slightly inflate. The level of the lake dropped almost 6 feet and formed a hardened lava high strand, or a “bathtub ring” where the high lava mark reached. The level of the lava lake has mostly held steady over the course of the day,. USGS reports that the depth of the lava lake was 580 feet at the 5:45pm this evening. To better track the depth of the lake, USGS has added a graphic tracking the depth to their website which also shows a very slowly draining lava lake. The volume of the lake is currently estimated at ~5.6 billion gallons of lava. (https://www.usgs.gov/media/images/graph-showing-depth-halema-uma-u-lava-lake-k-lauea-volcano) Images and captions from USGS, captions in the order images appear: Image 1 - The Kīlauea summit eruption within Halema‘uma‘u crater continues this evening with no major changes from earlier today, December 27. The western fissure vents (right) remain active. A HVO scientist makes observations of the ongoing activity. Mauna Loa Volcano is visible in the background. USGS photo taken at approximately 5:45 p.m. HST on December 27 by F. Trusdell. Image 2 - The ongoing eruption at Kīlauea Volcano's summit, within Halema‘uma‘u crater, has formed a lava lake that is now being fed by one fissure at its western end. The lake reached its greatest height and extent on December 25, but draining into the now-inactive north vent lowered the lava level by several meters (yards). This left a berm of lava that now bounds the slightly smaller lake, within which there are several islands, the two largest of which are marked in yellow. A dashed blue line indicates the extent of the water lake that existed in the crater until December 20, and a dashed black line indicates the extent of the 2008–2018 lava lake in Halema‘uma‘u. Image 3 - Live thermal image of Halemaʻumaʻu taken at 8:38pm and the lava lake from the west rim of the new summit collapse features [F1cam]. Camera link https://www.usgs.gov/volcanoes/kilauea/f1cam-halema-uma-u-thermal-image-west-rim-new-summit-collapse-features Image 4 - Graph showing the depth of the Halema‘uma‘u crater lava lake at Kīlauea Volcano's summit. HVO scientists measure the Kīlauea summit lava level using a small laser rangefinder mounted on a tripod. Measurements began one day after the start of the eruption on December 20, 2020 and are updated by geologists making observations from the field.