The current understanding of tsunamis generated by volcanic-island landslides is reliant on numerical models benchmarked against reconstructions of past events. As the largest historical event with ...timed tsunami observations, the 1888 sector collapse of Ritter Island, Papua New Guinea provides an outstanding opportunity to better understand the linked process of landslide emplacement and tsunami generation. Here, we use a combination of geophysical imaging, bathymetric mapping, seafloor observations and sampling to demonstrate that the Ritter landslide deposits are spatially and stratigraphically heterogeneous, reflecting a complex evolution of mass-flow processes. The primary landslide mass was dominated by well-bedded scoriaceous deposits, which rapidly disintegrated to form an erosive volcaniclastic flow that incised the substrate over much of its pathway. The major proportion of this initial flow is inferred to have been deposited up to 80 km from Ritter. The initial flow was followed by secondary failure of seafloor sediment, over 40 km from Ritter. The most distal part of the 1888 deposit has parallel internal boundaries, suggesting that multiple discrete units were deposited by a series of mass-flow processes initiated by the primary collapse. The last of these flows was derived from a submarine eruption triggered by the collapse. This syn-collapse eruption deposit is compositionally distinct from pre- and post-collapse eruptive products, suggesting that the collapse immediately destabilised the underlying magma reservoir. Subsequent eruptions have been fed by a modified plumbing system, constructing a submarine volcanic cone within the collapse scar through at least six post-collapse eruptions. Our results show that the initial tsunami-generating landslide at Ritter generated a stratigraphically complex set of deposits with a total volume that is several times larger than the initial failure. Given the potential for such complexity, there is no simple relationship between the volume of the tsunamigenic phase of a volcanic-island landslide and the final deposit volume, and deposit area or run-out cannot be used to infer primary landslide magnitude. The tsunamigenic potential of prehistoric sector-collapse deposits cannot, therefore, be assessed simply from surface mapping, but requires internal geophysical imaging and direct sampling to reconstruct the event.
•Ritter Island's sector collapse provides an exemplar of volcanic tsunami hazards.•Deposit heterogeneity reflects erosion, secondary failure and a triggered eruption.•The volume of the distal deposit alone far exceeds the tsunamigenic failure.•A single catastrophic collapse led to stratigraphically complex distal deposits.•Accurate assessment of tsunami potential requires internal imaging and sampling.
The impacts of volcanic eruptions on climate are increasingly well understood, but the mirror question of how climate changes affect volcanic systems and processes, which we term “climate-volcano ...impacts”, remains understudied. Accelerating research on this topic is critical in view of rapid climate change driven by anthropogenic activities. Over the last two decades, we have improved our understanding of how mass distribution on the Earth’s surface, in particular changes in ice and water distribution linked to glacial cycles, affects mantle melting, crustal magmatic processing and eruption rates. New hypotheses on the impacts of climate change on eruption processes have also emerged, including how eruption style and volcanic plume rise are affected by changing surface and atmospheric conditions, and how volcanic sulfate aerosol lifecycle, radiative forcing and climate impacts are modulated by background climate conditions. Future improvements in past climate reconstructions and current climate observations, volcanic eruption records and volcano monitoring, and numerical models all have a role in advancing our understanding of climate-volcano impacts. Important mechanisms remain to be explored, such as how changes in atmospheric circulation and precipitation will affect the volcanic ash life cycle. Fostering a holistic and interdisciplinary approach to climate-volcano impacts is critical to gain a full picture of how ongoing climate changes may affect the environmental and societal impacts of volcanic activity.
•Reconstruction of Anak Krakatau's eruptive activity following Dec. 2018 collapse.•No evidence for the collapse being triggered by intrinsic magmatic changes.•Failure resulted from extensive ...instabilities, accumulated from edifice growth.•Sudden unloading perturbed the magmatic system, causing intense volcanic activity.•Monitoring edifice growth may isolate areas prone to edifice instability.
The lateral collapse of Anak Krakatau volcano, Indonesia, in December 2018 highlighted the potentially devastating impacts of volcanic edifice instability. Nonetheless, the trigger for the Anak Krakatau collapse remains obscure. The volcano had been erupting for the previous six months, and although failure was followed by intense explosive activity, it is the period immediately prior to collapse that is potentially key in providing identifiable, pre-collapse warning signals. Here, we integrate physical, microtextural and geochemical characterisation of tephra deposits spanning the collapse period. We demonstrate that the first post-collapse eruptive phase (erupting juvenile clasts with a low microlite areal number density and relatively large microlites, reflecting a crystal-growth dominated regime) is best explained by instantaneous unloading of a relatively stagnant upper conduit. This was followed by the second post-collapse phase, on a timescale of hours, which tapped successively hotter and deeper magma batches, reflected in increasing plagioclase anorthite content and more mafic glass compositions, alongside higher calculated ascent velocities and decompression rates. The characteristics of the post-collapse products imply downward propagating destabilisation of the magma storage system as a response to collapse, rather than pre-collapse magma ascent triggering failure. Importantly, this suggests that the collapse was a consequence of longer-term processes linked to edifice growth and instability, and that no indicative changes in the magmatic system could have signalled the potential for incipient failure. Therefore, monitoring efforts may need to focus on integrating short- and long-term edifice growth and deformation patterns to identify increased susceptibility to lateral collapse. The post-collapse eruptive pattern also suggests a magma pressurisation regime that is highly sensitive to surface-driven perturbations, which led to elevated magma fluxes after the collapse and rapid edifice regrowth. Not only does rapid regrowth potentially obscure evidence of past collapses, but it also emphasises the finely balanced relationship between edifice loading and crustal magma storage.
The edifice of Yate volcano, a dissected stratocone in the Andean Southern Volcanic Zone, has experienced multiple summit collapses throughout postglacial time restricted to sectors NE and SW of the ...summit. The largest such historic event occurred on 19th February 1965 when ∼6.1–10 × 10
6
m
3
of rock and ice detached from 2,000-m elevation to the SW of the summit and transformed into a debris flow. In the upper part of the flow path, velocities are estimated to have reached 40 m s
−1
. After travelling 7,500 m and descending 1,490 m, the flow entered an intermontane lake, Lago Cabrera. A wavemaker of estimated volume 9 ± 3 × 10
6
m
3
generated a tsunami with an estimated amplitude of 25 m and a run-up of ∼60 m at the west end of the lake where a settlement disappeared with the loss of 27 lives. The landslide followed 15 days of unusually heavy summer rain, which may have caused failure by increasing pore water pressure in rock mechanically weathered through glacial action. The preferential collapse directions at Yate result from the volcano’s construction on the dextral strike-slip Liquiñe-Ofqui fault zone. Movement on the fault during the lifetime of the volcano is thought to have generated internal instabilities in the observed failure orientations, at ∼10° to the fault zone in the Riedel shear direction. This mechanically weakened rock may have led to preferentially orientated glacial valleys, generating a feedback mechanism with collapse followed by rapid glacial erosion, accelerating the rate of incision into the edifice through repeated landslides. Debris flows with magnitudes similar to the 1965 event are likely to recur at Yate, with repeat times of the order of 10
2
years. With a warming climate, increased glacial meltwater due to snowline retreat and increasing rain, at the expense of snow, may accelerate rates of edifice collapse, with implications for landslide hazard and risk at glaciated volcanoes, in particular those in strike-slip tectonic settings where orientated structural instabilities may exist.
The Sierra Nevada Volcanic Range (SNVR), which includes Popocatépetl, Iztaccíhuatl and Tláloc-Telapón volcanoes, has been the source of multiple large explosive eruptions that have dispersed tephra ...across central México. Several eruptions since 40 ka have previously been described, particularly from Popocatépetl, the southernmost volcano of the range. However, the longer-term eruption history of the SNVR is poorly understood, due to challenges with correlating limited exposures of older pyroclastic sequences, and in discriminating between tephras derived from different sources. Here we describe two extensive exposures located between Popocatépetl and Iztaccíhuatl volcanoes, which provide a more complete and longer-term explosive eruption record of the SNVR: the Nepopualco and Xalitzintla tephra sequences. A detailed tephrostratigraphic survey, together with new 40Ar/39Ar geochronological analyses and glass geochemistry, has permitted the characterization of identified eruption units further leading to the determination of geochemical fields for each volcano and the subsequent discernment of volcanic sources. Our results show that, since the collapse of the Los Pies Cone, which destroyed the Paleo-Iztaccíhuatl edifice at 631 ± 44 ka (2σ), Iztaccíhuatl has produced at least 6 explosive rhyolitic eruptions. After coeval activity with Popocatépetl, between ~600 and ~500 ka, Iztaccíhuatl's explosive activity ceased while Popocatépetl's continued until present day. Popocatépetl has produced at least 27 medium to large explosive eruptions (inferred VEI 4–6), commonly of andesitic to dacitic compositions. Some of these eruptions deposited pumice fallout of >1 m thick in both the Nepopualco and Xalitzintla sequences (e.g. the 339 ± 16 ka 2σ NT-23/WRT-7 eruption), suggesting that Popocatépetl has produced several eruptions similar in magnitude to the well-known ~14 ka Tutti Frutti Pumice (a VEI 6 eruption with a ~5 km3 tephra volume). The Popocatépetl and Iztaccíhuatl tephras are interbedded with deposits from more distal volcanoes, including some mafic to intermediate products of unknown sources (possibly from nearby monogenetic cones) and tephras related to the late Pleistocene eruptions of Tláloc-Telapón (including the tephra layer produced by the San Valentin Ignimbrite, recently 40Ar/39Ar dated in this study at ~102 ka; 2σ). Our new chemical, stratigraphic and geochronologic investigations of these pyroclastic deposits, predominantly from Popocatépetl and Iztaccíhuatl, provide information on the scale and frequency of medium to large magnitude explosive eruptions over a longer-time period than currently known and that have had potential to disperse tephra across central México since the middle to late Pleistocene. This new data can be used to determine the source of further unknown tephras in the region as well as to better assess the volcanic hazard to the densely populated megalopolis of México City.
•Detailed explosive eruptive history of Popocatépetl, Iztaccíhuatl & Tláloc-Telapón.•New 40Ar/39Ar eruption ages provide constraints on the Late Pleistocene volcanism.•Glass shard major element analyses distinguish different eruption deposits.•Glass compositions can also be used to identify the source volcano.
Seismic activity has been postulated as a trigger of volcanic eruption on a range of timescales, but demonstrating the occurrence of triggered eruptions on timescales beyond a few days has proven ...difficult using global datasets. Here, we use the historic earthquake and eruption records of Chile and the Andean southern volcanic zone to investigate eruption rates following large earthquakes. We show a significant increase in eruption rate following earthquakes of
M
W
>
8, notably in 1906 and 1960, with similar occurrences further back in the record. Eruption rates are enhanced above background levels for ~
12 months following the 1906 and 1960 earthquakes, with the onset of 3–4 eruptions estimated to have been seismically influenced in each instance. Eruption locations suggest that these effects occur from the near-field to distances of ~
500 km or more beyond the limits of the earthquake rupture zone. This suggests that both dynamic and static stresses associated with large earthquakes are important in eruption-triggering processes and have the potential to initiate volcanic eruption in arc settings over timescales of several months.
Marine sediments around volcanic islands contain an archive of volcaniclastic deposits, which can be used to reconstruct the volcanic history of an area. Such records hold many advantages over often ...incomplete terrestrial data sets. This includes the potential for precise and continuous dating of intervening sediment packages, which allow a correlatable and temporally constrained stratigraphic framework to be constructed across multiple marine sediment cores. Here we discuss a marine record of eruptive and mass‐wasting events spanning ∼250 ka offshore of Montserrat, using new data from IODP Expedition 340, as well as previously collected cores. By using a combination of high‐resolution oxygen isotope stratigraphy, AMS radiocarbon dating, biostratigraphy of foraminifera and calcareous nannofossils, and clast componentry, we identify five major events at Soufriere Hills volcano since 250 ka. Lateral correlations of these events across sediment cores collected offshore of the south and south west of Montserrat have improved our understanding of the timing, extent and associations between events in this area. Correlations reveal that powerful and potentially erosive density‐currents traveled at least 33 km offshore and demonstrate that marine deposits, produced by eruption‐fed and mass‐wasting events on volcanic islands, are heterogeneous in their spatial distribution. Thus, multiple drilling/coring sites are needed to reconstruct the full chronostratigraphy of volcanic islands. This multidisciplinary study will be vital to interpreting the chaotic records of submarine landslides at other sites drilled during Expedition 340 and provides a framework that can be applied to the stratigraphic analysis of sediments surrounding other volcanic islands.
Key Points
Biostratigraphy, isotope geochemistry, and clast componentry of IODP Site U1396
Deposits are correlated across sites to the south and south west of Montserrat
Results highlight the spatial heterogeneity of deposits around volcanic islands
Late Glacial and Holocene soils and sediments in southern Chile contain an important record of explosive volcanic activity since the end of the last glaciation, and have considerable potential for ...the development of a regional tephrostratigraphical framework. This paper reports the discovery of several new tephra deposits from the Hualaihue region (∼42° S) of southern Chile. Eruption sizes, constrained from field observations, and ages, constrained by 25 new radiocarbon dates, show that the volcanoes of the Hualaihue peninsula have had relatively few explosive, tephra-generating eruptions during the Holocene. An eruption of Apagado deposited ∼1 km
3 of bedded basaltic scoria at ∼2.6 calibrated (cal) ka BP, and Hornopirén produced a similar, but volumetrically-smaller unit at ∼5.7 cal ka BP. Activity at Yate over the same time period has been predominantly characterised by lava production, although small explosive eruptions, the products of which span a range of compositions, have also occurred, including one at ∼0.9 cal ka BP. The northern part of the regional tephra sequence is dominated by andesitic pumice fall deposits derived from Calbuco volcano. These include deposits from several eruptions during a 3500-year-long period at the start of the Holocene, as well as two large explosive eruptions in the past 2000 years. A distinctive rhyolitic tephra layer that is interbedded with the locally derived tephra sequence is the Cha1 unit, from Chaitén volcano, 108 km south of Hornopirén. This rhyolitic pumice deposit, dated at ∼9.75 cal ka BP, is the largest volumetrically of those described here, with a volume of 3.5 km
3. This new tephrostratigraphy covers a region whose volcanic history was previously very little known, and contributes to a regional record of large explosive eruptions that now spans a 500 km-long segment of the southern Andean arc, between Calbuco and Hudson volcanoes.
Recent studies hypothesize that some submarine slides fail via pressure‐driven slow‐slip deformation. To test this hypothesis, this study derives pore pressures in failed and adjacent unfailed deep ...marine sediments by integrating rock physics models, physical property measurements on recovered sediment core, and wireline logs. Two drill sites (U1394 and U1399) drilled through interpreted slide debris; a third (U1395) drilled into normal marine sediment. Near‐hydrostatic fluid pressure exists in sediments at site U1395. In contrast, results at both sites U1394 and U1399 indicate elevated pore fluid pressures in some sediment. We suggest that high pore pressure at the base of a submarine slide deposit at site U1394 results from slide shearing. High pore pressure exists throughout much of site U1399, and Mohr circle analysis suggests that only slight changes in the stress regime will trigger motion. Consolidation tests and permeability measurements indicate moderately low (~10−16–10−17 m2) permeability and overconsolidation in fine‐grained slide debris, implying that these sediments act as seals. Three mechanisms, in isolation or in combination, may produce the observed elevated pore fluid pressures at site U1399: (1) rapid sedimentation, (2) lateral fluid flow, and (3) shearing that causes sediments to contract, increasing pore pressure. Our preferred hypothesis is this third mechanism because it explains both elevated fluid pressure and sediment overconsolidation without requiring high sedimentation rates. Our combined analysis of subsurface pore pressures, drilling data, and regional seismic images indicates that slope failure offshore Martinique is perhaps an ongoing, creep‐like process where small stress changes trigger motion.
Key Points
Permeability and pressure measurements were made on submarine slide deposits
Near‐lithostatic fluid pressures exist between low‐permeability clays in many slide deposits
Small stress changes can trigger additional shearing and slow‐slip failure in some slide sediments
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