Magma reservoir failure and the onset of caldera collapse at Kīlauea Volcano in 2018

Abstract

Caldera-forming eruptions are among Earth’s most hazardous natural phenomena, yet the architecture of subcaldera magma reservoirs and the conditions that trigger collapse are poorly understood. Observations from the formation of a 0.8–cubic kilometer basaltic caldera at Kīlauea Volcano in 2018 included the draining of an active lava lake, which provided a window into pressure decrease in the reservoir. We show that failure began after <4% of magma was withdrawn from a shallow reservoir beneath the volcano’s summit, reducing its internal pressure by ~17 megapascals. Several cubic kilometers of magma were stored in the reservoir, and only a fraction was withdrawn before the end of the eruption. Thus, caldera formation may begin after withdrawal of only small amounts of magma and may end before source reservoirs are completely evacuated.

Unexpected large eruptions from buoyant magma bodies within viscoelastic crust

“…At Kilauea, interpretation of geodetic measurements finds pressure drop prior to onset of caldera collapse to be~17 MPa (ref. 50 ), similar to what we find for the Bárðarbunga collapse. In the activity east of Mayotte, drainage from a deep magma body (>20 km depth) in the mantle is inferred 51,53 where the host rock is viscoelastic.…”

“…Individual elements of the modelling framework presented here (viscoelastic host rock behaviour, magma buoyancy, sustained magma channel, development of underpressure to initiate caldera collapse) may help to understand large volume eruptions in general. The most recent large volume effusive eruptions on Earth include the rift eruption at Kilauea volcano in 2018 when~0.8 km 3 of magma erupted in relation to summit caldera collapse 38,50 , and the ongoing submarine eruption east of the Mayotte island, Indian Ocean, which began in May 2018 and where more than 5 km 3 of magma have erupted [51][52][53] . At Kilauea, interpretation of geodetic measurements finds pressure drop prior to onset of caldera collapse to be~17 MPa (ref.…”

The cascading origin of the 2018 Kīlauea eruption and implications for future forecasting

“…In 2008, a lava lake formed in Halemaʻumaʻu crater 42,43 (Fig. 1b), at the volcano's summit 20 km uprift from Puʻu ʻŌʻō, and persisted until the start of the 2018 eruption 1,3 .…”

“…The LERZ eruption drained magma from the summit reservoir, 40 km away, at rates exceeding 100 m 3 s −1 , causing rapid summit deflation 3 . By mid-May, the summit lava lake had drained and the floor of Halemaʻumaʻu crater disintegrated in a piece-meal fashion, accompanied by several small explosive events (Fig.…”

“…An apparent increase in the rate of summit drainage after the earthquake supports the notion that the M w 6.9 earthquake boosted transport rates in the magmatic system 3 . If the M w 6.9 earthquake did enhance magma transport to the LERZ, this might, in part, explain the comparatively large erupted volume that triggered structural failure at the summit 3 . In comparison, the 1955 and 1960 LERZ eruptions occurred in a similar area of the rift zone but were much smaller (0.1-0.3 km 3 ) 5,68 , were not associated with ≥M6 south flank earthquakes, and did not produce large-scale collapse at the summit.…”