The Evolution of the Popocatépetl Volcanic Complex: Constraints on Periodic Edifice Construction and Destruction by Sector Collapse

Popocatépetl is one of the most active volcanoes in North America. Its current predominantly mild activity is contrasted by a history of large effusive and explosive eruptions and sector collapse events, which was first summarised by Espinasa-Pereña and Martin-Del Pozzo (2006). Since then, a wealth of new radiometric, geophysical and volcanological data has been published, requiring a re-evaluation of the evolution of the Popocatépetl Volcanic Complex (PVC). Herein, we combine existing literature with new field observations, aerial imagery and digital elevation model interpretations to produce an updated and improved reconstruction of the growth and evolution of the PVC through all of its history. This will be fundamental for the assessment and mitigation of risks associated with potential future high-magnitude activity of the PVC. The PVC consists of four successive volcanic edifices separated by three sector collapse events producing avalanche deposits: Tlamacas (>538 - >330 ka, described here for the first time), Nexpayantla (∼330 - >96 ka), Ventorrillo (∼96 ka - 23.5 ka) and Popocatépetl (<23.5ka) edifices. The newly described Tlamacas collapse propagated towards ENE forming part of the Mayorazgo avalanche deposit.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5709190

New Evidence to Support Zephyria Tholus as a Composite Volcano on Mars

Zephyria Tholus has been proposed to be a composite volcano, however, detailed geomorphological study was not carried out due to limited high-resolution remote sensing data. Here we use MOLA, THEMIS, CTX and HiRISE data to conduct topographical and geomorphological analysis of Zephyria Tholus. We identify extensive valleys and troughs on the flank, which are sector collapse or glacio-fluvial in origin. The valleys and troughs indicate coexistence of different erosion resistance materials, along with the observed solid lava outcrops. There are also layered materials identified on the wall of the largest valley. In addition, perched craters are identified on the top depression and flanks of Zephyria Tholus, indicating the presence of ice-rich layer. We conducted crater size-frequency distribution of the caldera and found the absolute model age is 3.74 (+0.03, −0.04) Ga. The geomorphology evidence and chronology result support the composite volcano nature of Zephyria Tholus, and indicate the magma volatile content in the Aeolis region in Noachian is more than 0.15 wt% if the atmosphere paleo-pressure was similar to present Mars.

A channelised debris-avalanche deposit from Pirongia basaltic stratovolcano, New Zealand

A newly discovered, large volume (3.3 km3) volcanic debris-avalanche is described from the Pirongia Volcano in North Island, New Zealand. Mapping, field surveys and drill core data were used to reconstruct the distribution and facies of the deposit (the Oparau breccia). The debris avalanche was channelised into a lowland graben structure resulting in a prolonged runout distance of ≥20 km and substantial thickness of >200 m in medial areas. The deposit contains block and matrix facies dominated by ankaramite basalt sampled from the oldest parts of the volcanic edifice. The age of deposition of the Oparau breccia is constrained to the period 2.2-1.75 Ma. The collapse source zone is marked by a prominent unconformity on the southwestern flank of the mountain. Movement on faults within the graben is identified as the most likely cause of sector collapse. The collapse scarp is infilled by 5 km3 of post-collapse volcanic material.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5505549

Landslide-tsunamis along the flanks of Mount Epomeo, Ischia: propagation patterns and coastal hazard for the Campania coasts, Italy

Ischia Island has been repeatedly affected by mass collapses, which are mainly caused by the steepness of the main peak (Mt. Epomeo) and by phenomena related to its volcanic activity.The most relevant cases of mass failure studied in the literature and postulated to be tsunamigenic cover a wide spectrum of sizes, from sector collapse to small-volume mass transports. Tsunamis generated by landslides in Ischia may affect the coast of the Campania mainland, including the Gulf of Naples.The focus of this work is the evaluation of the pattern of the maximum tsunami energy. To this purpose, we perform a series of numerical simulations by moving the same landslide source in different hypothetical positions around the island. The landslide dynamics is computed through the code UBO-BLOCK, and the tsunami propagation by employing the code UBO-TSUFD, both in-house developed. The final goal is to characterize the coastal areas of the Campania mainland most exposed to tsunami attack from Ischia sources.It is found that the position of the landslide influences deeply the distribution of the tsunami elevation in the coastal stretch north of the Procida Mount, while, remarkably, it is irrelevant inside the Gulf of Naples where the bathymetric effect prevails.

Volcanic Lateral Collapse Processes in Mafic Arc Edifices: A Review of Their Driving Processes, Types and Consequences

Volcanic cones are frequently near their gravitational stability limit, which can lead to lateral collapse of the edifice, causing extensive environmental impact, property damage, and loss of life. Here, we examine lateral collapses in mafic arc volcanoes, which are relatively structurally simple edifices dominated by a narrow compositional range from basalts to basaltic andesites. This still encompasses a broad range of volcano dimensions, but the magma types erupted in these systems represent the most abundant type of volcanism on Earth and rocky planets. Their often high magma output rates can result in rapid construction of gravitationally unstable edifices susceptible both to small landslides but also to much larger-scale catastrophic lateral collapses. Although recent studies of basaltic shield volcanoes provide insights on the largest subaerial lateral collapses on Earth, the occurrence of lateral collapses in mafic arc volcanoes lacks a systematic description, and the features that make such structures susceptible to failure has not been treated in depth. In this review, we address whether distinct characteristics lead to the failure of mafic arc volcanoes, or whether their propensity to collapse is no different to failures in volcanoes dominated by intermediate (i.e., andesitic-dacitic) or silicic (i.e., rhyolitic) compositions? We provide a general overview on the stability of mafic arc edifices, their potential for lateral collapse, and the overall impact of large-scale sector collapse processes on the development of mafic magmatic systems, eruptive style and the surrounding landscape. Both historical accounts and geological evidence provide convincing proofs of recurrent (and even repetitive) large-scale (&gt;0.5 km3) lateral failure of mafic arc volcanoes. The main factors contributing to edifice instability in these volcanoes are: (1) frequent sheet-like intrusions accompanied by intense deformation and seismicity; (2) shallow hydrothermal systems weakening basaltic rocks and reducing their overall strength; (3) large edifices with slopes near the critical angle; (4) distribution along fault systems, especially in transtensional settings, and; (5) susceptibility to other external forces such as climate change. These factors are not exclusive of mafic volcanoes, but probably enhanced by the rapid building of such edifices.

Multi-scale impacts of Antuco basaltic stratovolcano (Southern Andes, Chile) ca. 6.2 ka sector collapse: avalanche deposition, eruptive behavior transformation and hydrologic reconfiguration

&lt;p&gt;Reconstructing the complex processes triggered by catastrophic destruction of volcanoes on both their own magmatic system and the surrounding landscape, is a fundamental task for evaluating long-timescale volcanic hazards and controls on the development of volcanoes. Antuco stratovolcano (37.4&amp;#176;S, 71.4&amp;#176;W; Chile), is a dominantly basaltic composite edifice which original ca. 3300 m altitude edifice experienced a ca. 5 km&lt;sup&gt;3&lt;/sup&gt; Bandai-type sector collapse at ~6.2 ka BP. We carried out field studies of its debris avalanche deposit (DAD), which was distributed to the W and consist of chaotic breccias, with a longitudinal facies transformation from 2 large proximal toreva-block facies (4 &amp; 9 km W from the scar) to megablocks, blocks and matrix facies in distal areas (up to 20 km from the scar). Basal facies are fine grained shredded rocks and contain substratum injections and clastic dykes. The surface of the avalanche is hummocky, and the size, internal architecture and lithology of hummocks vary with distance. At El Pe&amp;#241;&amp;#243;n and Manquel (10 to 20 km W from the scar) the DAD is overlaid by a sequence of dilute pyroclastic density currents (PDCs) containing juvenile ash and highly vesicular porphyritic basalt scoria fine to medium lapilli size. Further W, one of the latest dilute PDC gave ca. 3.4 ky BP in charcoal. &amp;#160;These PDCs are separated from two thick, far-reaching basaltic andesite overlying lava flows (post-collapse Antuco basal flows) by a paleosol, and they show compositional features consistent with mixing of a highly zoned or compartmentalised magma storage system at &lt;5km depth. Subsequently, that event was followed by the initiation of a renewed basaltic magmatic stage and cone regeneration at Antuco during the Late Holocene to the present. These observations plus the detailed study of the composition and texture of post-collapse products suggests a long-lasting reconfiguration of the plumbing system in response to depressurization induced by the sector collapse. The DAD also blocked the natural output of Lake Laja, increasing its level ca. 200 m and then triggering catastrophic outburst floods by dam rupture, preserved as alluvial beds interpreted as debris and hyperconcetrated flow deposits. The ancestral Laja lake outburst, eroded and redeposited tens of meters of basaltic sediments and boulders as far as 120 km within the Central Depression, W from the volcano. Downstream, along the Itata and Biob&amp;#237;o rivers (the latter fed by Laja River) at least two fluvial/alluvial terraces are formed by these volcaniclastic materials, 140-170 km WNW from Antuco volcano. These deposits develop laminar, cross bedded and flaser structures. In addition, fragments of pumice, charcoal and archaeological ceramics have been recognised in the sediments. Ceramics where likely produced at the Talcahuano-1 archaeological site (ca. 1.890 BP), in agreement with charcoal that provides a maximum age between 1.8 and 1.85 ky BP for the younger flooding events. The coupled investigation of the impacts produced by massive debris avalanches, especially at basaltic-arc stratovolcanoes, is important to understand their long-term system evolution and hazards.&lt;/p&gt;

Volcanic Hazard Assessment for an Eruption Hiatus, or Post-eruption Unrest Context: Modeling Continued Dome Collapse Hazards for Soufrière Hills Volcano

Effective volcanic hazard management in regions where populations live in close proximity to persistent volcanic activity involves understanding the dynamic nature of hazards, and associated risk. Emphasis until now has been placed on identification and forecasting of the escalation phase of activity, in order to provide adequate warning of what might be to come. However, understanding eruption hiatus and post-eruption unrest hazards, or how to quantify residual hazard after the end of an eruption, is also important and often key to timely post-eruption recovery. Unfortunately, in many cases when the level of activity lessens, the hazards, although reduced, do not necessarily cease altogether. This is due to both the imprecise nature of determination of the “end” of an eruptive phase as well as to the possibility that post-eruption hazardous processes may continue to occur. An example of the latter is continued dome collapse hazard from lava domes which have ceased to grow, or sector collapse of parts of volcanic edifices, including lava dome complexes. We present a new probabilistic model for forecasting pyroclastic density currents (PDCs) from lava dome collapse that takes into account the heavy-tailed distribution of the lengths of eruptive phases, the periods of quiescence, and the forecast window of interest. In the hazard analysis, we also consider probabilistic scenario models describing the flow’s volume and initial direction. Further, with the use of statistical emulators, we combine these models with physics-based simulations of PDCs at Soufrière Hills Volcano to produce a series of probabilistic hazard maps for flow inundation over 5, 10, and 20 year periods. The development and application of this assessment approach is the first of its kind for the quantification of periods of diminished volcanic activity. As such, it offers evidence-based guidance for dome collapse hazards that can be used to inform decision-making around provisions of access and reoccupation in areas around volcanoes that are becoming less active over time.

The rebirth and evolution of Bezymianny volcano, Kamchatka after the 1956 sector collapse

Continued post-collapse volcanic activity can cause the rise of a new edifice. However, details of such edifice rebirth have not been documented yet. Here, we present 7-decade-long photogrammetric data for Bezymianny volcano, Kamchatka, showing its evolution after the 1956 sector collapse. Edifice rebirth started with two lava domes originating at distinct vents ~400 m apart. After 2 decades, activity became more effusive with vents migrating within ~200 m distance. After 5 decades, the activity focused on a single vent to develop a stratocone with a summit crater. We determine a long-term average growth rate of 26,400 m3/day, allowing us to estimate the regain of the pre-collapse size within the next 15 years. Numerical modeling explains the gradual vents focusing to be associated with loading changes, affecting magma pathways at depth. This work thus sheds light on the complex regrowth process following a sector collapse, with implications for regrowing volcanoes elsewhere.

Transport and Evolution of Supercritical Fluids During the Formation of the Erdenet Cu–Mo Deposit, Mongolia

Petrological and fluid inclusion data were used to characterize multiple generations of veins within the Erdenet Cu–Mo deposit, Mongolia, and constrain the evolution of fluids within the magmatic–hydrothermal system. Three types of veins are present (from early to late): quartz–molybdenite, quartz–pyrite, and quartz. The host rock was emplaced at temperatures of 700–750 °C, the first quartz was precipitated from magma-derived supercritical fluids at 650–700 °C, quartz–molybdenite and quartz–pyrite veins were formed at ~600 °C, and the quartz veins were precipitated in response to retrograde silica solubility caused by decreasing temperatures at <500 °C. We infer that over-pressured fluid beneath the cupola caused localized fluid injection, or that accumulated stress caused ruptures and earthquakes related to sector collapse; these events disrupted impermeable layers and allowed fluids to percolate through weakened zones.