USGS Preliminary Analysis_LERZ_7-15-18_v1.1

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maddening energy against the sides of the awful caldron, as to shake the solid earth above, and to detach huge masses of overhanging rocks, which, leaving their ancient beds, plunged into the fiery gulf below. So terrific was the scene that no one dared to approach near it, and travellers [sic] on the main road, which lay along the verge of the crater, feeling the ground tremble beneath their feet, fled and passed by at a distance ... Every thing [sic] within the caldron is new. Not a particle of lava remains as it was when I last visited it. All has been melted down and re -cast. All is new." While the summit and rift zone activities bear some similarities to 2018 events, the chronological order is reversed with the summit's apparent collapse preceding the LERZ eruption in 1840 while the 2018 summit collapse started after the LERZ eruption began. 1924 LERZ intrusion (HVO website) After years of rising lava levels within, and overflows from, Halema'uma'u crater, the lava lake dropped out of sight in February 1924. It was followed by an earthquake swarm that began in early April, reaching a peak on April 23 with ground cracking, faulting, at least 3.6 m (12 ft) of coastal subsidence, and hundreds of felt earthquakes indicating the intrusion of magma from the summit into the LERZ. Ultimately, no lava was erupted. "Halema'uma'u Crater was 115 m (377 ft) deep following the draining of the lake. As seismicity waned in lower Puna, the crater floor began to collapse on April 29, deepening to more than 150 m (490 ft) on May 1 and nearly 210 m (690 ft) on May 7. Frequent dust clouds indicated continuing collapse in the following days." "... more than 50 explosive events during a 2.5 -week period in May 1924. The explosions were then, and remain today, the most powerful at Kilauea since the early 19th century, throwing blocks weighing as much as 14 tons from the crater. Halema'uma'u doubled in diameter, deepened to about 400 m (1300 ft), and drastically changed in behavior—for the next 85 [sic; 84] years it no longer hosted a long- lived lava lake, until one returned in 2008." Although there was no LERZ eruption due to this activity, the subsidence and plentiful earthquakes suggested an intrusion similar to the 2018 intrusion and it was followed by summit collapse and explosive events. No evidence of an offshore eruption has been found after several submarine expeditions in the area. 1955 LERZ eruption: February 28—May 26 (see Macdonald and Eaton, 1964) The 1955 LERZ eruption lasted for 88 days, but consisted of three eruptive periods separated by pauses in activity. The first period of the eruption lasted from February 28 to March 7 (8 days), and consisted of fissures that extended 5.7 km (3.5 mi) from Puu Honuaula to Kapoho Crater, along a trend overlapping the eastern part of the 2018 fissure system, but north of it. The 1955 fissures generally propagated to the 13