Search

Unrest began in July 2021 at Askja volcano in the Northern Volcanic Zone (NVZ) of Iceland. Its most recent eruption, in 1961, was predominantly effusive and produced ∼0.1 km3 lava field. The last plinian eruption at Askja occurred in 1875. Geodetic measurements between 1983 and 2021 detail subsidence of Askja, decaying in an exponential manner. At the end of July 2021, inflation was detected at Askja volcano, from GNSS observations and Sentinel‐1 interferograms. The inflationary episode can be divided into two periods from the onset of inflation until September 2023. An initial period until 20 September 2021 when geodetic models suggest transfer of magma (or magmatic fluids) from within the shallowest part of the magmatic system (comprising an inflating and deflating source), potentially involving silicic magma. A following period when one source of pressure increase at shallow depth can explain the observations. Plain Language Summary: Askja volcano, situated in the Northern Volcanic Zone in Iceland, has been quiet since its last eruption in 1961, with surface deformation measurements from 1983 to 2021 displaying a decaying subsidence signal within the Askja caldera. However, at the end of July 2021, the volcano began to inflate. This was detected on both GNSS and satellite observations. As of September 2023, ∼65 cm of uplift had been measured at GNSS station OLAC. Modeling of surface deformation measurements indicates that the inflation was triggered by upward migration of melt (or magmatic fluids). Key Points: At the end of July 2021, Askja volcano began to inflate—detected on both GNSS and satellite observations, ending 1983–2021 subsidenceGeodetic modeling indicates upward migration of magma, feeding a magma body at an inferred depth of 2.5–3.1 km under the main Askja calderaStart of unrest was associated with magma transfer within the upper part of the system, followed by possible additional influx from depth [ABSTRACT FROM AUTHOR]

In 2018 Kı̄lauea volcano erupted a decade's worth of basalt, given estimated magma supply rates, triggering caldera collapse. Yet, less than 2.5 years later Kı̄lauea re‐erupted. At the 2018 eruption onset, pressure within the summit reservoir was ∼20 MPa above magmastatic. By the onset of collapse this decreased by ∼17 MPa. Analysis of magma surges at the 2018 fissures, following collapse events, implies excess pressure at the eruption end of only ∼1 MPa. Given the new vent elevation, ∼11–12 MPa pressure increase was required to bring magma to the surface in December 2020. Analysis of Global Positioning System data between 8/2018 and 12/2020 shows there was a 73% probability that this condition was met at the onset of the 2020 eruption. Given a plausible range of possible vent elevations, there was a 40%–88% probability of sufficient pressure to bring magma to the surface 100 days before the eruption. Plain Language Summary: In 2018 Kı̄lauea volcano erupted so much lava that, based on long‐term magma supply rates, one might have anticipated a decade long quiescence. Yet Kı̄lauea erupted in December 2020 less than 2.5 years later. Volcano deformations are used to infer pressure changes within magma systems. However, large inelastic deformations during Kı̄lauea's 2018 caldera collapse prohibit this approach. Here, we utilize diverse observations to infer the pressure history within the magma system during the inter‐eruptive period. Analysis of magma surges following caldera collapse events suggests that the pressure available to drive flow was very low at the end of the 2018 eruption. Due to unique observations of lava lake drainage in 2018 eruption, we were able to use Global Positioning System displacements to estimate the pressure increase between the end of the 2018 eruption and the start of the 2020 eruption. Given that eruption was most likely between the bottom of the 2018 pit and the top of the largest down‐dropped block, we show that there was a high probability that reservoir pressure was sufficient to bring magma to the surface well before the 2020 eruption. Our approach could aid future eruption forecasting. Key Points: Time predictable estimate based on 2018 erupted volume and long‐term magma supply rate greatly overestimates the post 2018 repose periodModeling magma surges following collapse events shows driving pressures at the end of collapse cycles of only ∼1 MPaWe estimate a 73% chance of pressure sufficient to raise magma to the 20 December 2020 eruptive vents based on Global Positioning System data up to that date [ABSTRACT FROM AUTHOR]

On January 12, 2020, Taal volcano, Philippines, erupted after 43 years of repose, affecting more than 500,000 people. Using interferometric synthetic aperture radar (InSAR) data, we present the pre‐ to post‐eruption analyses of the deformation of Taal. We find that: (1) prior to eruption, the volcano experienced long‐term deflation followed by short‐term inflation, reflecting the depressurization‐pressurization of its ∼5 km depth magma reservoir; (2) during the eruption, the magma reservoir lost a volume of 0.531 ± 0.004 km3 while a 0.643 ± 0.001 km3 lateral dike was emplaced; and (3) post‐eruption analyses reveal that the magma reservoir started recovery approximately 3 weeks after the main eruptive phase. We propose a conceptual analysis explaining the eruption and address why, despite the large volume of magma emplaced, the dike remained at depth. We also report the unique and significant contribution of InSAR data during the peak of the crisis. Plain Language Summary: Taal volcano in the Philippines erupted on January 12, 2020. Here, we present the pre‐, co‐, and post‐eruption data, model, and analyses using interferometric synthetic aperture radar (InSAR) data acquired by various satellite systems. We find that: (1) prior to the eruption, the volcano experiences a sequence of long‐term (>1 year) deflation followed by short‐term (≤1 year) inflation as a result of the depressurization‐pressurization of its ∼5 km depth magma reservoir; (2) during the eruption, the magma reservoir lost a volume of 0.531 ± 0.004 km3 while a 0.643 ± 0.001 km3 lateral dike was emplaced; and (3) post‐eruption analyses reveal that the magma reservoir is in recovery starting ∼3 weeks after the main eruptive phase. We propose a conceptual analysis to explain the 2020 Taal eruption and the dike emplacement. We also report the unique and significant contribution of remote sensing data, particularly InSAR during the peak of the crisis. Key Points: We present a comprehensive interferometric synthetic aperture radar (InSAR)‐based data, analyses, and models of Taal's pre‐ to post‐eruptive stateDuring the eruptive crisis, Taal's magma reservoir lost 0.531 ± 0.004 km3 of volume while a 0.643 ± 0.001 km3 lateral dike was emplacedLow‐latency InSAR‐derived products provided crucial and significant information to PHIVOLCS during the January 2020 eruptive event [ABSTRACT FROM AUTHOR]

We conducted gravity surveys of the summit area of Kīlauea Volcano, Hawaiʻi, in November 2018 and March 2019, with the goal of determining whether there was any mass change at depth following the volcano's May–August 2018 caldera collapse. Surface deformation between the two surveys was minimal, but we measured a gravity increase (maximum 44 μGal) centered on the caldera that can be modeled as mass accumulation in a region ~1 km beneath the surface. We interpret this mass increase to be mostly magma accumulation in void space that was created during the summit collapse. Caldera uplift was evident by April 2019, indicating that the magma volume had reached a point where pressurization could be sustained. Modeled gravity change suggests a maximum magma storage rate at Kīlauea's summit during November 2018 to March 2019 that is much less than the pre‐2018 magma supply rate to the volcano. Plain Language Summary: Measuring changes in gravity over time at a volcano provides an indication of mass variation beneath the surface, which can offer evidence of whether or not magma is accumulating in, or draining from, subsurface reservoirs. After the 2018 collapse of Kīlauea Volcano, Hawaiʻi, there was uncertainty over the status of subsurface magmatic activity. We found that an increase in gravity occurred between November 2018 and March 2019. The gravity increase was not accompanied by uplift of the surface, which implies that mass, probably magma, was accumulating in void space created during the collapse. The rate of magma accumulation was much less than the pre‐2018‐collapse magma supply rate. By April 2019 Kīlauea was inflating, indicating that the magma reservoir beneath the summit had filled to the point that pressure could be sustained. Key Points: A gravity increase following the 2018 collapse of the summit of Kīlauea Volcano, Hawaiʻi, indicates mass accumulation in void space ~1 km beneath the surfaceThe maximum magma storage rate determined from gravity and deformation is much less than the pre‐collapse magma supply rate to the volcanoGravity monitoring provides an important means of assessing subsurface magma storage and supply rates as Kīlauea recovers from its 2018 collapse [ABSTRACT FROM AUTHOR]