100 Years Ago on Kīlauea: The Last Overflow of Halemaʻumaʻu

INTRODUCTION 100 years ago, Kīlauea also hosted a lava lake within Halemaʻumaʻu crater, yet the scene was much different than today. For starters, the lava level had been much higher during the previous 4 years, fluctuating between ~1200 to ~1300 feet above its current 2021 elevation (~350 to ~400 m) as it repeatedly overflowed its rim. The massive overflow of March 1921 would be the last for over a century, “long remembered as the most tremendous fiery display of Kilauea overflow of this Hawaiian cycle,” Dr. Thomas Jaggar wrote. “Never in the past decade had Halemaumau presented so brilliant, large, and continuous a sheet of liquid lava overflowing its rim.” Kīlauea’s Halemaʻumaʻu crater hosted five lava pools named the central lake, east and west ponds, the southeast pool and the southwest arm (Figure 2 - February 8 and March 14 maps). The entire sequence was documented by Dr. Thomas Jaggar, founder and first director of the Hawaiian Volcano Observatory. LEAD UP TO THE OVERFLOW “At the beginning of March the continued subsidence of the lava in the pit made the scene surpassingly impressive owing to the great inner crags towering above the five lava lakes. The walls around the several lakes were sheer precipices, 70 feet high in places, and the rim of the pit stood 90 feet above the liquid lava.” (Figure 3 - March 10) As the lava levels within the five pools began to rise from March 14-16, 1921, Dr. Jaggar describes the scene (Figure 4 - March 16): “An astonishing transformation had taken place in the new islet of the central lake. It had lifted bodily by a swelling upward of the lake bottom around it, to become an immense hill with the flat islet standing like a thin-stemmed wine glass on top of it. This mass stood 40 feet above the lake. The tilted toadstool on top threatened to fall at any minute.” “The whole mass had lifted faster than the lake and filled a great part of the lake area.” THE ~1-WEEK LAVA SURGE As the early Hawaiian Volcano Observatory registered an increase in earthquakes and harmonic tremor in the early hours of March 18, 1921, Dr. Jaggar made his way back to Halemaʻumaʻu: “From [the] rim of [the] pit at south pressure ridge a most sensational change was found to have taken place, in contrast to the dull crusted lava of the previous evening, forty feet down. The lakes were now 4 feet below the east margin of the pit, all merged into a small sea of fountaining lava with the crags standing high as islands, and the liquid was brimming over the southwestern and northern sides. ... The liquid was rising rapidly.” (Figure 5 - March 25) “The several pools of lava of Halemaumau were marked only by fountaining areas, with fountains not so numerous as in December, but with more large centers of effervescence separated by surfaces as skin. All the crags were islands. The hollows north and northeast of Halemaumau had filled evenly with an extension of the lake backed by a new rampart of slabby crusts, and this during the high level greatly enlarged the actual lake surface beyond the limits of the pit.” “Very large fountains had started a cauldron of gas release and depressed lava in what had been the east corner of the southeast pool. Towards this focus there were inrushing currents from east pond, south channel and central lake. The action increased until this stormy center of activity was the most conspicuous feature of the eruption, the inflow from the other pools frequently becoming cascades into the vortex at the cauldron. The immense fountains built a black glassy rampart grotto and flung up clouds of droplets and filaments that formed deep cindery beds to leeward, southwest of Halemaumau.” (Figure 1 - March 19) “The fountains made a swishing sound like the surf and had the quality of the Mauna Loa fountains, only the lava was much more viscous. Every now and then spurts of brown fume violently blown up from below rose through the storm of fountaining. Individual fountains were of the ʻperpetual’ type, with flings 15 to 20 feet high, but much of the time the cauldron was a roaring abyss of hundreds of fountains indistinguishable as units ... Kilauea was never more spectacular.” LAVA FLOWS “The overflow northeast swept down for a mile in the Volcano House direction, crossed the trail, and made aa lava at its front.” This flow also consumed the nearby tool hut: “Its contents were water barrels, crow-bars, shovels, hammers and some pipes, lumber and furniture, belonging to the Observatory.” “The longest flow was pouring all over the southern end of Kilauea Crater and out through a gap in the wall ... where it advanced a third of a mile into the desert and stopped.” The inner caldera had been breached at an elevation of 3625 feet above sea level (1105 m). The lava flow was aided by a cone 500 feet to the southwest of the lake, known as the “Red Solfatara”, which also connected to the lava column and erupted with the rising lava. (Figure 6 - March 20) “There was a slight lowering of the lava lake, [and it] had become a Niagara of complicated lava falls, pouring into northern and eastern cauldrons. .. As the greater cascades were from 50 to 100 feet wide and the fall fully 40 feet, something of the grandeur of this fiery maelstrom can be imagined. The whole pit was resolved into three parts, quiet source pools southwest and west, rapid torrents center and southeast, gigantic cascades and churning cauldrons, north and east.” (Figure 7 - March 21) WHIRLWINDS “This activity was accompanied by whirlwinds generated by uprush of hot gas.” One “developed a basal breadth of 800 feet, migrating across the east rim of Halemaumau.” Another “started in the south cauldron and migrated back and forth over the hot rapids inside the pit. Fragments were carried up 700 feet. The lava was drawn up into what appeared to be streamers of red flame. Whenever the spout migrated over a crag or the brink of the pit it became blackened with lava particles. After action for 20 minutes with loud roaring noise, this whirl expended itself… Larger fragments seen close at hand as they struck the ground were red hot and pasty; one of these on the west side of the pit was 52 inches long and 20 inches greatest width, and must have weighed over 40 pounds.” “Much scoriaceous glassy lava was blown about, which gave rise to false reports of an explosive eruption. ... Hot whirlwinds are common here, but these were unusually large.” BACK TO BACKGROUND “The end of the month started a rapid sinking away of the lava column to the hundred-foot level. This was the closing stage of the eruptive crisis, and the fire-pit resumed its more normal condition, with scores of fountains, numerous islands and crags, lava cascades pouring into wells, and shifting surface currents across the incandescent lake.” “Crags and lake lowered ten feet or more per day, whirlpool and shifting sink-holes formed, the crags and islets increasingly emerged, fume grew thicker, and lines of traveling fountains .. became conspicuous features. The noise, glow and heat greatly diminished. The flow on the Kilauea floor ceased when the subsidence began and impressive underground chambers were revealed at the two source cones, with wells surrounded by glowing stalactites, and banners of pale flame.” (Figure 8 - April 4) 100-YEAR PERSPECTIVE While the “normal” of 100 years ago is quite different from today, it is interesting to consider whether the activity in 2021 could eventually lead to a similar volcanic landscape as described by Dr. Jaggar. The lava presently filling Halemaʻumaʻu crater appears to be cooling and degassing at the surface rather than draining back underground, such that it may already be forming a semi-solid material similar to the crags and bottom of the 1921 lava ponds. From this perspective, the biggest difference today may be that Kīlauea’s lava is not forced to erupt through this material and puddle onto its already-hardened surface. Yet the 2021 West Vent continues to be further submerged by lava accumulating in the crater, so could a change could be coming if the current eruption persists long enough to completely drown the vent? Or will a future summit eruption emerge through the cooling lava body, rather than around it? Only time will tell if the lava ponds of 100 years ago will return, and if we are witnessing the start of that process. SOURCES Bevens, D., T.J. Takahashi, and T.L. Wright, eds. 1988. The Early Serial Publications of the Hawaiian Volcano Observatory. 3 v. vols. Hawaii National Park: Hawaii Natural History Association. Fiske, R.S., T. Simkin, and E.A. Nielsen, eds. 1987. The Volcano Letter. Washington, DC: Smithsonian Institution Press. Jaggar, T.A., Jr. 1947. “Origin and Development of Craters.” Geological Society of America Memoir 21, 508 p. Original photographs by Dr. Thomas Jaggar, colorized by Dane DuPont.