Geodetic observations indicate the presence of a flat-topped sill-like magma reservoir at ~2 km depth below the caldera 6, 7, 22, giving a low roof thickness to caldera diameter aspect ratio of ~0.25 (compared to >1.0 for Kilauea and Bárðarbunga). Past eruptions occurred on both circumferential and radial fissure systems, with evidence for topographic control of dike orientation 14, 21. It has a large elliptical summit caldera, 9.5 km by 7.5 km wide and 100 m deep 19, 20 (Fig. Sierra Negra is an 1100 m high shield volcano on Isabela Island, Galápagos (Fig. Integration of geodetic, seismic, and geochemical observations through the eruption cycle of a Galápagos caldera offers the possibility of new insights into critical processes, thus starting to fill a major gap in our understanding of basaltic volcanism. Consequently, there are no multidisciplinary studies of the volcanic processes underpinning Galápagos Island volcanism. However, despite their significance, the Islands’ remote location means that no previous eruption has been monitored by a local, ground-based, geodetic, and seismic network. In addition, the wide calderas and shallow depths of magma reservoirs of Sierra Negra and Alcedo result in low roof thickness to diameter ratios 10, 17, 18. Galápagos Island volcanoes have generally not developed subaerial rift zones, like systems in Hawaii or the Canary Islands, which exert a first-order control on shallow magma migration and emplacement, and subsequent caldera formation. This distinction has been furthered by observations from satellite data of prolonged surface uplift and trapdoor faulting 6, 16. The steep upper flanks, large calderas 8, 12, 13, and circumferential and radial eruptive fissures 14, 15 of the volcanoes of the western Galápagos Islands distinguish them from more intensively studied basaltic systems in Hawaii and Iceland. Although resurgence is well documented over long time scales at silicic calderas 11, it is rare at basaltic systems, and suggests fundamental differences between Galápagos calderas and archetypes in Hawaii and Iceland.

In addition, elevated intra-caldera topography indicates that these are sites of long-term uplift or resurgence 7, 9, 10, rather than subsidence. In contrast, some basaltic calderas in the Galápagos Islands, Ecuador, exhibit several metres of uplift and intense seismicity for years before eruptions 6, 7, 8. However, the minor pre-eruptive uplift and seismicity preceding these eruptions provided little warning of the scale of these forthcoming events. 3, 4), involved rapid subsidence along caldera-bounding ring faults of >500 (ref. These observations reveal the importance of intra-caldera faulting in affecting resurgence, and the mechanisms of eruption in the absence of well-developed rift systems.īasaltic calderas are the sites of some of the largest deformation events on Earth. Although co-eruptive magma withdrawal resulted in 8.5 m of subsidence, net uplift of the inner-caldera on a trapdoor fault resulted in 1.5 m of permanent resurgence. Magma supply to a shallow reservoir drove 6.5 m of pre-eruptive uplift and seismicity over thirteen years, including an Mw5.4 earthquake that triggered the eruption. Here we combine a unique multiparametric dataset to show how the 2018 eruption of Sierra Negra contributed to caldera resurgence. However, a scarcity of observations has obscured the mechanisms underpinning such behaviour. These systems also display long-term intra-caldera uplift, or resurgence. In contrast, some eruptions at Galápagos Island volcanoes are preceded by prolonged, large amplitude uplift and elevated seismicity. Recent large basaltic eruptions began after only minor surface uplift and seismicity, and resulted in caldera subsidence. Nature Communications volume 12, Article number: 1397 ( 2021) Caldera resurgence during the 2018 eruption of Sierra Negra volcano, Galápagos Islands

Most recent volcano eruption 2018