Volcano‐Tectonic Activity at Deception Island Volcano Following a Seismic Swarm in the Bransfield Rift (2014–2015)

Abstract

In September 2014 there was a sharp increase in the seismic activity of the Bransfield Strait, Antarctica. More than 9,000 earthquakes with magnitudes up to 4.6 located SE of Livingston Island were detected over a period of 8 months. A few months after the series onset, local seismicity at the nearby (∼35 km) Deception Island volcano increased, displaying enhanced long‐period seismicity and several outbursts of volcano‐tectonic (VT) earthquakes. Before February 2015, VT earthquakes occurred mainly at 5–20 km SW of Deception Island. In mid‐February the numbers and sizes of VT earthquakes escalated, and their locations encompassed the whole volcanic edifice, suggesting a situation of generalized unrest. The activity continued in anomalously high levels at least until May 2015. Given the spatial and temporal coincidence, it is unlikely that the Livingston series and the Deception VT swarm were unrelated. We propose that the Livingston series may have produced a triggering effect on Deception Island volcano. Dynamic stresses associated to the seismic swarm may have induced overpressure in the unstable volcanic system, leading to a magmatic intrusion that may in turn have triggered the VT swarm. Alternatively, both the Livingston earthquakes and the VT swarm could be consequences of a magmatic intrusion at Deception Island. The Livingston series would be an example of precursory distal VT swarm, which seems to be a common feature preceding volcanic eruptions and magma intrusions in long‐dormant volcanoes.

Deciphering the evolution of Deception Island’s magmatic system

“…Our results lead us to interpret that the magma imaged by geophysical studies 54,75 beneath DI corresponds to a combination of: (i) non-eruptible magma residues of the reservoir responsible for the caldera-forming event; (ii) magma remnants stagnated in chambers that developed during the post-caldera stage; and (iii) possible magma batches newly intruded in the last decades as suggested by the monitoring data recorded during the volcanic unrest episodes that happened in 1992, 1999, and 2014–2015 (e.g., 7,8,39 ). Indeed, magma plumbing systems of similar configuration have been described for other calderas worldwide such as Santorini (Greece) 68 .…”

“…However, the usual presence of DI tephras in distal (> 500 km distance) marine sediments 4 and ice cores 5,6 hints that several past eruptions may have been significantly larger and more violent (VEI > 4–5). The recorded historical volcanic activity, the recently experienced eruptions (1967, 1969, and 1970) and the unrest episodes happened in 1992, 1999 7 , and 2014–2015 8 categorise DI as a very active volcano. Therefore, the occurrence of future volcanic activity would become a serious cause for concern for scientists (see for instance the destruction of the recent Chilean and British scientific bases), technical and logistic personnel, and tourists, staying on the island or nearby.…”

Volcanic Origin of a Long‐Lived Swarm in the Central Bransfield Basin, Antarctica

“…The 2020–2021 swarm overlaps with the shallow magnetic anomaly located northeast of the Orca volcano (Almendros et al., 2020; Olivet et al., 2021). Several other swarms connected with volcanic activity have also been observed along the Bransfield Ridge (Almendros et al., 2018; Dziak et al., 2010), but are mostly located in the western part of the ridge. No significant earthquakes have occurred in the central Bransfield basin since 1970 (Figure 1).…”

The timing and widespread effects of the largest Holocene volcanic eruption in Antarctica

“…Deception Island has erupted more than twenty times since the 19 th Century including three eruptions between 1967 and 1970 and seismic crises in 1992, 1999 and 2015 10 , 19 , 20 . Whilst these recent eruptions have been relatively modest in magnitude, the hitherto undated caldera-forming event ejected a dense-rock equivalent (DRE) of 30–60 km 3 of magma, comparable in volume to the catastrophic 1815 Tambora eruption that caused global cooling and resulted in “the year without a summer” 1 , 2 , 10 – 12 .…”