Major Explosive Event Research Articles

A Composite Seismic Source Model for the First Major Event During the 2022 Hunga (Tonga) Volcanic Eruption

AbstractThe violent eruption of the Hunga (Tonga) submarine volcano on 15 January 2022 caused a 58 km‐heigh ash plume, catastrophic tsunami, and significant global seismic and infrasound waves. However, the physical mechanism underpinning its multiple‐explosive events remains unclear, and its resolvability relies on the seismic waveform source inversion. The studies of two different point‐source models, the seismic moment tensor (MT) and the single force (SF), have been performed separately for this eruption, which, interestingly, can explain the seismic data adequately. Here, we use a joint inversion of MT and SF to unravel a composite source of an explosion‐like MT and a significant upward force for the first major explosive event. Regarding the direction and magnitude, we propose that the upward force is likely a rebound force in response to the pressure drop on the seafloor because the water body above the volcano was abruptly uplifted by the shallow underwater explosion.

A 22,000-year tephrostratigraphy record of unidentified volcanic eruptions from Ternate and Tidore islands (North Maluku, Indonesia)

Investigating past eruptions gives a unique opportunity to understand volcanic hazards, particularly in Indonesia, where volcanic eruptions occur frequently. Here, we present the first reconstruction of the eruptive history of the Ternate and Tidore Islands (North Maluku, Indonesia) over the past 22,000 years cal. BP, based on a new identification and characterization of past volcanic events methodological approach. This multidisciplinary study (geomorphology, tephrochronology, sedimentology, geochronology, geochemistry) constitutes the first stratigraphic and chronological continuum from volcanic deposits found in a set of fifteen sections established in Ternate, Tidore, and Maitara Islands. Sedimentological and geochemical data from tephrostratigraphy studies and radiocarbon dating suggest that these islands experienced at least four major explosive events from c. 22,000 to 740 years cal. BP. The oldest event recorded is a Plinian eruption associated with a caldera-forming eruption of Telaga volcano on Tidore Island at c. 22,000–17,500 cal. BP. A second pumiceous eruption dated at c. 18,000 cal. BP is attributed to the last Plinian eruption of Gamalama volcano on Ternate, whose current eruptive activity is mainly strombolian or phreatomagmatic. A succession of pyroclastic deposits of phreatomagmatic origin is related to the Ngade maar formation on Ternate Island, and the abundant deposits of scoria, pumice, and ash found in all sites probably occurred c. 14,500–13,000 cal. BP. No eruptions of the Kie Matubu volcano on Tidore Island have been reported by human beings since their presence in the region from the 16th century, but this study highlights two late Holocene eruptions, c. 2500 cal. BP and 740 cal. BP. This first chronostratigraphic framework from the late Pleistocene to recent eruptions in this region, sheds new light concerning the management of prediction and warning information about potential eruptions that may occur on these small volcanic islands in the future.

The Skaros effusive sequence at Santorini (Greece): Petrological and geochemical constraints on an interplinian cycle

Santorini volcanic complex (Greece) is the result of a long evolutionary history, marked by the alternation of explosive (Plinian) eruptions and interplinian low explosive/effusive eruptive cycles. Products emitted during the interplinian stages are well exposed along the rim of the calderic structure formed during the major Minoan (3.6 ka) Plinian eruption. We conducted a systematic sampling of the basaltic to dacitic lavas erupted by the interplinian volcanic centre of Skaros, active between 67 and 54 ka. The continuously exposed products of the Skaros lifecycle offer the tremendous opportunity to reconstruct the petrological evolution of the volcanic centre, and in turn to provide new insights on the behaviour of Santorini feeding system during interplinian stages. The combination of whole-rock, mineral chemistry and synchrotron X-ray computed microtomography analyses enabled us to decipher the main physico-chemical parameters of the Skaros plumbing system that drove ascent and differentiation processes of magmas. Results indicate that the main magma ponding zone beneath Skaros centre extended from 12 to 4 km b.s.l., where it underwent frequent refilling by basaltic melts. In the later evolutionary stage of the Skaros system, the basaltic replenishment became less frequent allowing the ultimate differentiation of magma towards dacitic composition. The shallow nature of the magma ponding zone, sited well above the H2O saturation depth, favoured the continuous degassing and inhibited the increase of vapor pressure during differentiation, preventing the onset of explosive eruptions, as in case of the major explosive events at Santorini.

Eruptive style and flow dynamics of the pyroclastic density currents related to the Holocene Cerro Blanco eruption (Southern Puna plateau, Argentina)

The Pleistocene-Holocene Cerro Blanco Volcanic Complex (CBVC), one of the youngest caldera complexes in the Southern Central Andes, is the source of possibly one of largest Holocene eruptions on Earth, the 4.2 ka, Cerro Blanco eruption. This caldera forming eruption is the younger of two major explosive events from the CBVC. Previous work has estimated the range from VEI 6 to 7, yet to date there is no detailed study of the stratigraphy and volcanology of the proximal deposits and dynamics of the Cerro Blanco eruption. Here we present the first detailed analysis of the eruptive products of the Holocene Cerro Blanco eruption that reveal the eruptive sequence highlighting the flow dynamics of the related pyroclastic density currents (PDCs). The PDCs were mainly inertia-dominated, however, channelization of parental PDCs into deep valleys resulted in the flow transformation to forced convection-dominated flows. In addition, topographic constriction in valleys enhanced the sedimentation rate producing regressive bed forms and ultimately the avulsion of the main path of the PDCs resulting in flooding of secondary valleys. A model is presented whereby simultaneous convective and collapsing eruptive column dynamics were established and sustained throughout the eruption. Towards its end, instabilities of the column occurred in response to the climax of a protracted incremental caldera collapse. This eruptive sequence is similar to those observed in well-documented small collapse calderas. An important unresolved issue for the CB eruption is it volume. The currently estimated volume of 83 km3 (DRE) by Fernando-Turiel et al. (2019) is inconsistent with the size of the Cerro Blanco caldera and to date the over thickening of the distal ash by local rework is poor assessed. Further work is needed to fully evaluate this mismatch and accurately estimate the volume of this important Holocene eruption.

Anatomy of the Xáltipan ignimbrite at Los Humeros Volcanic Complex; the largest eruption of the Trans-Mexican Volcanic Belt

The Xáltipan ignimbrite (ca. 290 km3 DRE) represents the major explosive event from Los Humeros Volcanic Complex (LHVC) that can be ranked as the largest caldera-forming eruption of the Trans-Mexican Volcanic Belt (TMVB). This eruption marked the onset of an explosive period of LHVC producing the collapse of the main Los Humeros caldera at 164 ± 4.2 ka. This paper provides a detailed characterization of the Xáltipan ignimbrite anatomy and eruptive chronology that records a multi-phase, single eruption. This eruption resulted in more complex architecture and lithofacies variations of the ignimbrite than previously reported. To support these findings, we present two representative composite Xáltipan stratigraphic columns based on two regional reference sections, together with a welding lithofacies map, digital mapping, energy line projections, geologic sections and high-resolution petrophysical characterization (micro-CT, He-pycnometry). Additionally, we have reevaluated the magnitude (DRE volume), and the total erupted mass of the deposit by taking into account critical primary and post-emplacement processes such as lithic concentration, welding grade, and bulk loss due to erosion. The internal architecture of the Xáltipan ignimbrite is composed of two flow units and two pumice fallout deposits (a basal one and an intercalated layer), which formed as a result of a voluminous and sequential eruption that can be resumed in four eruptive phases. The initial stage of the eruption produced a basal pumice fallout (BPF) (phase 1) derived from a buoyant plume that eventually collapsed, generating pyroclastic density current (PDC) deposits with intra-ignimbrite pumice fallout beds. This event was followed by the climactic, caldera-forming, boiling over-type eruptive phase (phase 2) that generated voluminous PDCs of the lower flow unit (LFU). As the eruption waned, a brief eruptive hiatus occurred, immediately followed by a second explosive event in the western rim of the caldera with a boiling-over type eruptive column depositing a discrete pumice fallout layer (IPF) (phase 3), which later collapsed depositing less voluminous PDC (UFU) in the western flank of the Los Humeros caldera (phase 4). The anatomy of the deposits shows that the Xáltipan ignimbrite was emplaced in different behaviors: radially in the proximal parts and channelized and confined in the distal parts, showing significant welding variations that range from non-to-highly welded conditions (welding ranks I-VI) controlled mainly by the paleotopography. The size calculations indicate that the deposits have an aerial extent of ca. 4600 km2, an ejected bulk volume of ca. 330 km3 with a DRE volume of ca. 290 km3, and an ejected mass of 1.1 × 1012 kg, which points out to a paroxysmal eruption (VEI 6-7).

Tephra and cryptotephra in a ~ 60,000-year-old lacustrine sequence from the Fucino Basin: new insights into the major explosive events in Italy

Two cores were sampled in the Fucino Basin (central Apennines, Italy), which represents an extensional intramountain basin filled by Pliocene to Quaternary continental alluvial and lacustrine deposits. The cores were investigated for tephra content and five visible tephras with thickness ranging from 1 to 8 cm were identified. Six additional cryptotephra were identified during the inspection of significant peaks of the magnetic susceptibility curve. Texture and mineralogy of five tephra and six cryptotephra layers were analyzed by means of scanning electron microscope coupled with energy-dispersive X-ray spectrometry system (SEM-EDS) and geochemical measurements were performed by an electron microprobe (EPMA) equipped with five wavelength-dispersive spectrometers (WDS) and using a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) system on single glass shards. The results allowed us to assign tephra and cryptotephra to ten known volcanic eruptions that occurred over the last ca. 60 ka in the Campanian Province (Phlegrean Fields and Ischia Island), the Alban Hills volcanic complex, and Lipari island. In particular, we recognized the deposits of the Monte Epomeo Green Tuff and the Piroclastiti di Catavola eruptions of Ischia, the pre-Campanian Ignimbrite Tlc, the Campanian Ignimbrite and the Neapolitan Yellow Tuff eruptions of the Phlegrean Fields, the Gabellotto-Fiume Bianco eruption of Lipari, and all the four explosive events belonging to the last cycle of volcanic activity of Albano maar (Albano 4–7). Deposits from five of these identified events (i.e., Piroclastiti di Catavola, Gabellotto-Fiume Bianco, Albano 5 and 6 eruptions, and Campanian Ignimbrite) were previously un-reported in the Fucino basin. These findings add new tephra layers to the list of possible tephrochronologic markers in the region and highlight that a comprehensive tephra record may be constructed when the study of cryptotephra layers is included. Moreover, results provide insights into the most recent volcanic activity of Albano maar, allowing us to date the onset of activity at the maar system at ca. 40 ka and to estimate the ages of all four eruptions that made up this eruptive sequence at ca. 37.5 ka (Albano 5), ca. 36.5 ka (Albano 6) and ca. 36 ka (Albano 7), respectively. Our work extends the known dispersal of several major explosive events, suggesting the intensity and magnitude appraisals, and attended risk scenario’s need to be revised using improved records of distal fall out.

Explosive eruption of El Chichón volcano (Mexico) disrupted 6th century Maya civilization and contributed to global cooling

Abstract A remarkably long period of Northern Hemispheric cooling in the 6th century CE, which disrupted human societies across large parts of the globe, has been attributed to volcanic forcing of climate. A major tropical eruption in 540 CE is thought to have played a key role, but there is no consensus about the source volcano to date. Here, we present evidence for El Chichón in southern Mexico as the most likely candidate, based on a refined reconstruction of the volcano’s eruption history. A new chronological framework, derived from distal tephra deposits and the world’s largest Holocene beach ridge plain along the Gulf of Mexico, enabled us to positively link a major explosive event to a prominent volcanic sulfur spike in bipolar ice core records, dated at 540 CE. We speculate that voluminous tephra fall from the eruption had a severe environmental impact on Maya societies, leading to temporary cultural decline, site abandonment, and migration within the core area of Maya civilization.

Earthquake history at the eastern boundary of the South Taupo Volcanic Zone, New Zealand

ABSTRACTAt the eastern boundary of the south Taupo Rift, the NE-striking, rift-bounding Rangipo and the ENE-striking Wahianoa active normal faults intersect. We investigate their intersection at the Upper Waikato Stream to understand the kinematics of a rift termination in an active volcanic area. The Upper Waikato Stream Fault is a previously unrecognised seismogenic source also at the eastern boundary, capable of producing a MW6.5 and up to MW7.1 earthquake if it ruptures in conjunction with the Rangipo or Wahianoa faults. We found a minimum of 12 surface-rupturing earthquakes in the last 45.16 ka on the Upper Waikato Stream Fault (mean slip-rate c. 0.5 mm/yr), and a minimum of nine surface-rupturing earthquakes in the last 133 ka on the Wahianoa Fault (mean slip-rate c. 0.2 mm/yr). Periods of highest slip-rate on these faults may coincide in time with Taupo, Ruapehu or Tongariro eruptions, but, despite their intersection, movement was not coincident across all faults. The Upper Waikato Stream Fault responded to a major Taupo Volcano eruption, the Wahianoa to a major eruptive sequence from Mt Tongariro and the Rangipo to major explosive events from Mt Ruapehu.

The ∼1000-years BP explosive eruption of Caldeira Volcano (Faial, Azores): the first stage of incremental caldera formation

The ∼1000-years BP eruption of Caldeira Volcano (Faial Island) was one of the last major explosive events recorded in the Azores. It produced a complex succession of pyroclastic deposits, known as the C11, divided into three members. At the base is the Brejo Member, a sequence of fine- to coarse-grained parallel-bedded ash layers found in the NW sector of the island. The middle part corresponds to the Inverno Member, a coarse-grained massive pumice fall deposit, restricted to the north flank of Caldeira Volcano. The top is dominated by the Cedros Member which includes massive to diffuse-stratified lapilli-ash and lithic breccias, exposed along the north and east flanks of the volcano. A minimum bulk volume of at least 0.22 km3 (>0.1 km3 dense rock equivalent (DRE)) is estimated for the C11 eruption, although a large portion may have been deposited offshore. The juvenile products are trachytic (59 wt% SiO2) with a homogenous whole-rock composition and mineral assemblage throughout the pyroclastic succession. However, petrographic and groundmass glass analyses indicate magma mingling/mixing processes between two trachytic batches. The C11 eruption history is divided into three phases (following the member division) with distinct eruptive styles: (1) an initial phreatomagmatic phase caused by rising magma (∼950 °C) encountering a crater pond or aquifer, (2) a fall-dominated phase which established a sub-Plinian column up to 14 km high (mass eruption rate (MER) of 1.2 × 107 kg/s) and (3) prolonged pyroclastic fountaining and sustained quasi-steady pyroclastic density current generation followed by summit collapse. The C11 eruption is interpreted as the first stage in the formation of an incremental caldera. This study provides valuable insights for a better understanding of small but complex explosive eruptions and their impact on ocean islands.

Coronal behavior before the large flare onset

Abstract Flares are a major explosive event in our solar system. They are often followed by a coronal mass ejection that has the potential to trigger geomagnetic storms. There are various studies aiming to predict when and where the flares are likely to occur. Most of these studies mainly discuss the photospheric and chromospheric activity before the flare onset. In this paper we study the coronal features before the famous large flare occurrence on 2006 December 13. Using the data from Hinode/Extreme ultraviolet Imaging Spectrometer (EIS), X-Ray Telescope (XRT), and Solar and Heliospheric Observatory (SOHO)/Extreme ultraviolet Imaging Telescope (EIT), we discuss the coronal features in the large scale (a few 100″) before the flare onset. Our findings are as follows. (1) The upflows in and around the active region start growing from ∼ 10 to 30 km s−1 a day before the flare. (2) The expanding coronal loops are clearly observed a few hours before the flare. (3) Soft X-ray and extreme ultraviolet intensity are gradually reduced. (4) The upflows are further enhanced after the flare. From these observed signatures, we conclude that the outer part of active region loops with low density was expanding a day before the flare onset, and the inner part with high density was expanding a few hours before the onset.

Volcanic evolution of the back-arc Pleistocene Payun Matru volcanic field (Argentina)

Abstract For the first time, about 30 volcanic formations of the back-arc Payun Matru volcanic field (Payun Matru volcanic field, Argentina, 36°S, 69°W) have been sampled for K–Ar geochronology and geochemistry in order to reconstruct the eruptive history of this key province in the Andean back-arc. The Payun Matru volcanic field has been built since final Pleistocene until present with ages ranging from 280 ± 5 to 7 ± 1 ka. Erupted lavas belong to calc-alkaline series, with characteristics of both arc and intraplate magmas. From previous studies, three main units are distinguished: (1) a basaltic field (Los Volcanes), which covers a large surface of the Payun Matru volcanic field, composed of strombolian cones and associated lava flows emitted from 300 ka to Holocene times, (2) the stratovolcano Payun, with intermediate compositions, built around 265 ka, and (3) the shield volcano Payun Matru s.s. characterized by trachytic compositions and a large summit caldera. The earlier stages of the Payun Matru volcano are not dated, but we constrain the major explosive event, related to the eruption of a widespread ignimbrite and to the formation of the caldera, between 168 ± 4 ka (internal wall of caldera) and 82 ± 1 ka (flow within the caldera). Based on the geochemical similarities of the ignimbrite and the upper lava flow of the pre-caldera cone, we suggest that the age of this event is most probably at the older end of this interval. Numerical modeling using a GIS program has been used to reconstruct the morphological evolution for Payun Matru volcano before and after the caldera collapse. The ancient edifice could be modeled as a flattened cone, 2300 m high, with a volume of about 240 km3. The ignimbrite eruption associated with the Payun Matru caldera formation could be related to the regional tectonic environment, which is characterized by multiple Plio-Pleistocene extensional stages during the last 5 Myr. The evolution of the Nazca plate subduction from a flat slab to a normal dip induced an input of fluid mobile elements and asthenosphere plume-like mantle source beneath the Patagonian lithosphere, which yields the observed intraplate signature. We also interpret this geodynamic evolution as the influence of extensive processes in the upper crust leading to caldera-forming eruptions as observed throughout this province.

TITAN2D simulations of pyroclastic flows at Cerro Machín Volcano, Colombia: Hazard implications

Cerro Machín is a dacitic tuff ring located in the central part of the Colombian Andes. It lies at the southern end of the Cerro Bravo–Cerro Machín volcanic belt. This volcano has experienced at least six major explosive eruptions during the last 5000 years. These eruptions have generated pyroclastic flows associated with Plinian activity that have traveled up to 8 km from the crater, and pyroclastic flows associated with Vulcanian activity with shorter runouts of 5 km from the source. Today, some 21,000 people live within a 8 km radius of Cerro Machín. The volcano is active with fumaroles and has shown increasing seismic activity since 2004, and therefore represents a potentially increasing threat to the local population. To evaluate the possible effects of future eruptions that may generate pyroclastic density currents controlled by granular flow dynamics we performed flow simulations with the TITAN2D code. These simulations were run in all directions around the volcano, using the input parameters of the largest eruption reported. The results show that an eruption of 0.3 km3 of pyroclastic flows from a collapsing Plinian column would travel up to 9 km from the vent, emplacing a deposit thicker than 60 m within the Toche River valley. Deposits >45 m thick can be expected in the valleys of San Juan, Santa Marta, and Azufral creeks, while 30 m thick deposits could accumulate within the drainages of the Tochecito, Bermellón, and Coello Rivers. A minimum area of 56 km2 could be affected directly by this kind of eruption. In comparison, Vulcanian column-collapse pyroclastic flows of 0.1 km3 would travel up to 6 km from the vent depositing >45 m thick debris inside the Toche River valley and more than 30 m inside the valleys of San Juan, Santa Marta, and Azufral creeks. The minimum area that could be affected directly by this kind of eruption is 33 km2. The distribution and thickness of the deposits obtained by these simulations are consistent with the hazard map presented by INGEOMINAS (Geological Survey of Colombia) in 2002. The composite map of the simulated flow deposits suggests that after major explosive events such as these, the generation of lahars is probable.

Seismic, acoustic, and thermal network monitors the 2003 eruption of Stromboli Volcano

The date 28 December 2002, heralded the onset of a 7‐month‐long effusive eruption at Stromboli volcano in Italy. The onset was accompanied on 30 December by a large landslide (Figure 1). This landslide produced a tsunami that damaged the villages on Stromboli and affected coastal zones around the southern Tyrrhenian Sea [Pino et al., 2004]. Following the landslide, the eruption was mostly characterized by effusive activity with lava flows extending from vents between 500 and 650 m above sea level. Simultaneously, Stromboli's typical explosive activity died out, with no explosions from the summit craters during the initial months of the eruption. However, a major explosive event on 5 April 2003 caused considerable alarm.

Aeromagnetic survey over an active stratovolcano in central Mexico

In this paper, we briefly summarize an aeromagnetic survey over a large stratovolcano (Popocatepetl) and surrounding volcanic terrain in central Mexico to show the potential that recent improvements in these methods have in studying active volcanoes. After a decades-long period of quiescence, the Popocatepetl volcano reawakened in 1994. Background seismicity showed a two-fold increase in October 1994. This was followed on 21 December by a swarm of volcano-tectonic events and tremors accompanying a large ash plume. Popocatepetl is an andesitic stratovolcano (Figure 1) in the central sector of the Plio-Quaternary Trans-Mexican volcanic belt (TMVB)—a continental arc associated with subduction of the Cocos and Rivera plates along the Middle Ainerican trench, and oriented almost E-W from the Pacific Ocean to the Gulf of Mexico. The TMVB volcanic-capped plateau is heavily populated. Mexico City is just 70 km away. Figure 1. Landsat thematic mapper image of the Iztaccihuatl-Popocatepetl volcanic range, eastern Mexico. The volcanic range is formed by several stratovolcanoes aligned north-south. Popocatepetl forms the southern end of a north-south trending range of large volcanic structures. The Popocatepetl stratovolcano has evolved through alternate periods of cone formation and destruction, with major cataclysmic events that destroyed ancient cones followed by formation of dome complexes and new summit cones. Recent activity at first was characterized by emission of ash rich in nonjuvenile material and volatiles, marked by intense seismicity with volcano-tectonic earthquakes (VT), long-period (LP) and tremor events. The ash and gas clouds from some events distributed ash over Mexico City and surrounding areas, with lapilli and small blocks falling over the volcano flanks. In March 1996, a dacitic dome built within the summit crater; magnetic activity to the present has been characterized by episodes of dome growth and destruction. Activity during December 2000 was particularly intense and, on 21 January 2001, a major explosive event …

Fragmental lava versus welded ignimbrite on Mount Etna: arguments inferred from crystal preferred orientation

Structural and textural similarities of some silicic lavas with strongly welded tuffs often lead to alternative interpretations of silicic rocks with doubtful origin. Such silicic “lavas” associated with pyroclastic deposits of benmoreitic composition were described on Mount Etna. In the first part of this paper we discuss the stratigraphic and lithologic arguments that lead to correlate these products with the “Cratere Ellittico” caldera. In a second part, we focus on the emplacement mechanism of these foliated “lava-like” flows and we reinterpret them as the result of welding and local rheomorphism of pyroclastic flow deposits. To discriminate between the two processes (fragmentation of a flowing lava or flattening of a fragmental deposit) we make a finite-strain analysis deduced from crystal orientation density distribution functions (DDF) in selected planes of the samples. Results of strain ratios show good agreement with previous values obtained by others on welded pyroclastic flow or welded air-fall deposits. We conclude that the “Cratere Ellittico” caldera is a major explosive event in the evolution of Etna. On the southwestern flank of the volcano the deposits of this eruption arc known as the Biancavilla-Montalto ignimbrite.

The contribution of volcanoes to the global atmospheric sulfur budget

A new assessment of the global volcanic emission rates of H2S, SO2, and SO42− is presented. The assessment is based on the development of a suitable classification of volcanic activity and its application to own measurements and measuring data given in the literature. Using this classification, the volcanic sulfur release is estimated to 1.18×107 t S/a total. This estimate must be regarded as a minimum since the data available for major explosive events are very uncertain. On the other hand the frequency of such events is comparatively low. We estimate a global volcanic emission of 1.52× 07 t SO2/a for the period 1961–1979. Our calculations show that in this period the total SO2 release during eruptive activities was at least 1.0×106 t SO2/a whereas about 14 times as much, namely 1.42×107 t SO2/a, were emitted during noneruptive activities. The importance of the contribution of the noneruptive activity has been neglected in earlier assessments. The average values for the global volcanic H2S and SO42− source strength are found to be around 106 t/a and 107 t/a, respectively. We conclude that during a period of very intensive volcanic activity around the world, like that which recently has started with the eruptions of Soufrière in 1979 and Mount St. Helens in 1980, the global sulfur release during eruptive events may become up to 1 order of magnitude higher than we have calculated but that nevertheless the sulfur emission during the noneruptive activity is dominating.