Increase In Eruption Rate Research Articles

The effects of unsteady effusion rates on lava flow emplacement: Insights from laboratory analogue experiments

The phenomenology of lava flow emplacement involves complex physical processes related to crystallization, eruption rate, temperature, crust solidification, and a variety of other factors. Changes in effusion rate are a natural part of lava flow emplacement and can complicate lava flow morphology and propagation. Analog experiments are a useful tool for investigating the role of changing effusion rates on flow propagation because they allow reasonably precise control of conditions and detailed documentation of resulting flows. Experimental datasets that investigate the impact of variable effusion rates on flow propagation can be used to enhance fundamental understanding of flow processes and to inform numerical models for hazards forecasts. In this study, we address the effects of decreasing and increasing eruption rates (Q) on four emplacement modes common to lava flows: resurfacing, marginal breakouts, inflation, and lava tubes. Laboratory analogue experiments using polyethylene glycol (PEG) 600 wax were used to derive Ψ, a dimensionless parameter that relates crust formation (ts) and lateral advection (ta) timescales of a viscous gravity current. We conducted 120 experiments using a peristaltic pump to inject dyed PEG wax into a chilled bath (∼ 0 °C) in a tank with a roughened base at a slope of 0°. The experiments were divided into two conditions: decreasing Q with time (condition 1) and increasing Q with time (condition 2). We controlled for volume of extruded wax, temperature, instantaneous eruption rate, Ψ, and duration of the decrease or increase in eruption rate. Results indicate that the duration of the pulsatory eruption rate, the experimental condition, initial Ψ, and the extruded volume influence the presence and strength of a crust (or lack thereof) which in turn influences the onset and extent of the four emplacement modes investigated. Prolonged increase in eruption rates favored resurfacing, widespread marginal breakouts and flow advancement, inflation, and some tube formation, while the specific morphology and area covered was controlled by an extensive, coherent crust, which in turn depended on initial Ψ and duration of the initial eruptive stage. Prolonged decreasing eruption rates promoted localized marginal breakouts, inflation, and tube formation. The duration of the pulse during the eruption rate change affected the likelihood and/or significance of the mode of emplacement. Similar observations were made on the early stages of the 2021 Fagradalsfjall eruption in Iceland to demonstrate the utility of the wax experiments in interpreting natural systems. Plain language summaryPredicting where lava will flow remains challenging due to the complex variables affecting its propagation. Lava is a multiphase fluid made of solids, liquids, and gas. In addition, as it cools, it forms a crust that can affect the flow. The eruption of lava is rarely steady over short and long timescales. This variability in eruption rate can also affect lava flow propagation and hence affect its predictability. Such variability in eruption rate may cause the flow to grow in thickness, in length, in width, or all of these simultaneously, and the style of growth affects the area impacted and controls where the flow is most hazardous. While numerical models have been useful in simulating flow advance on slopes, these models often simplify lava flow geometry and propagation mechanics. Laboratory analogue experiments allow for the reproduction of complex physics and morphology that closer approximate processes observed in nature. In this study, 120 experiments using PEG 600 – a water-soluble wax – were used to simulate lava flow emplacement under unsteady vent conditions. Flows were emplaced while increasing or decreasing the eruption rate during an eruption and the duration of the increase or decrease in eruption rate was varied along with other flow conditions. In the experiments, increasing or decreasing eruption rate at the vent, along with other parameters, impacted the formation of a cohesive or brittle crust, which in turn exerted strong control on whether the flows thickened or lengthened, affecting the area impacted and flow morphology. We map out lava flow characteristics in terms of these vent conditions, and compare our findings to a real eruption in Iceland.

Role of volatiles in highly explosive basaltic eruptions

Water and carbon dioxide are the most abundant volatile components in terrestrial magmas. As they exsolve into magmatic vapour, they promote magma buoyancy, accelerating ascent and modulating eruptive dynamics. It is commonly thought that an increase in pre-eruptive volatile content produces an increase in eruption intensity. Using a conduit model for basaltic eruptions, covering the upper 6 km of conduit, we show that for the same chamber conditions mass eruption rate is not affected by CO2 content, whereas an increase in H2O up to 10 wt.% produces an increase in eruption rate of an order of magnitude. It is only when CO2 is injected in the magma reservoir from an external source that the resulting pressurisation will generate a strong increase in eruption rate. Results also show that ascent velocity and fragmentation depth are strongly affected by pre-eruptive volatile contents demonstrating a link between volatile content and eruptive style.

An evaluation of Deccan Traps eruption rates using geochronologic data

Abstract. Recent attempts to establish the eruptive history of the Deccan Traps large igneous province have used both U−Pb (Schoene et al., 2019) and 40Ar/39Ar (Sprain et al., 2019) geochronology. Both of these studies report dates with high precision and unprecedented coverage for a large igneous province and agree that the main phase of eruptions began near the C30n–C29r magnetic reversal and waned shortly after the C29r–C29n reversal, totaling ∼ 700–800 kyr duration. These datasets can be analyzed in finer detail to determine eruption rates, which are critical for connecting volcanism, associated volatile emissions, and any potential effects on the Earth's climate before and after the Cretaceous–Paleogene boundary (KPB). It is our observation that the community has frequently misinterpreted how the eruption rates derived from these two datasets vary across the KPB. The U−Pb dataset of Schoene et al. (2019) was interpreted by those authors to indicate four major eruptive pulses before and after the KPB. The 40Ar/39Ar dataset did not identify such pulses and has been largely interpreted by the community to indicate an increase in eruption rates coincident with the Chicxulub impact (Renne et al., 2015; Richards et al., 2015). Although the overall agreement in eruption duration is an achievement for geochronology, it is important to clarify the limitations in comparing the two datasets and to highlight paths toward achieving higher-resolution eruption models for the Deccan Traps and for other large igneous provinces. Here, we generate chronostratigraphic models for both datasets using the same statistical techniques and show that the two datasets agree very well. More specifically, we infer that (1) age modeling of the 40Ar/39Ar dataset results in constant eruption rates with relatively large uncertainties through the duration of the Deccan Traps eruptions and provides no support for (or evidence against) the pulses identified by the U−Pb data, (2) the stratigraphic positions of the Chicxulub impact using the 40Ar/39Ar and U−Pb datasets do not agree within their uncertainties, and (3) neither dataset supports the notion of an increase in eruption rate as a result of the Chicxulub impact. We then discuss the importance of systematic uncertainties between the dating methods that challenge direct comparisons between them, and we highlight the geologic uncertainties, such as regional stratigraphic correlations, that need to be tested to ensure the accuracy of eruption models. While the production of precise and accurate geochronologic data is of course essential to studies of Earth history, our analysis underscores that the accuracy of a final result is also critically dependent on how such data are interpreted and presented to the broader community of geoscientists.

Glacial pumping of a magma-charged lithosphere: A model for glaciovolcanic causality in magmatic arcs

Glacial loading and unloading can influence the rates and timing of magmatism in tectonic settings where the lithosphere is relatively thin and hot. In continental arcs, where the lithosphere is substantially thicker, nominal loading by surface glaciers is unlikely to affect the production of subduction-related magmas. However, geologic evidence suggests that a causal linkage between volcanism and glaciations in arcs does exist. The last deglaciation of the Garibaldi volcanic belt in southwestern British Columbia, Canada saw a ∼5-fold volumetric increase in volcanism over the mean Pleistocene (background) rate that coincided with ∼400 m of rapid postglacial crustal uplift. Here, we use a cylindrical, thin plate bending approximation to calculate the horizontally oriented stresses developed in the crust during glacial loading/unloading (up to ±12 MPa). The distribution of compressive and extensional stresses is shown to modulate magma transport and storage by facilitating or suppressing magma ascent by dike propagation. We use Monte Carlo simulations to track the depth of upward migrating magma bodies in the crust over a single glacial cycle (i.e., during crustal depression and rebound). During loading, volcanism is suppressed as magma becomes trapped by compressive deviatoric stress in the upper part of the crust. During unloading, relaxation of this stress acts to release accumulated magma from the upper crust and causes an increase in eruption rate immediately following deglaciation. This model of “glacial pumping” of a magma-charged lithosphere suggests a causal linkage between volcanism and glaciation in volcanic arcs that explains the persistent observation that the volume and timing of volcanism is correlated with the major climate cycles.

Eruptive parameters and dynamics of the April 2015 sub-Plinian eruptions of Calbuco volcano (southern Chile)

We conducted geological and petrological analyses of the tephra fallout and pyroclastic density current (PDC) products of the 22-23 April 2015 Calbuco eruptions. The eruptive cycle consisted of two sub-Plinian phases that generated > 15 km height columns and PDCs that travelled up to 6 km from the vent. The erupted volume is estimated at 0.38 km3 (non-DRE), with approximately 90% corresponding to tephra fall deposits and the other 10% to PDC deposits. The erupted products are basaltic-andesite, 54-55 wt.% SiO2, with minor amounts of andesite (58 wt.% SiO2). Despite the uniform composition of the products, there are at least four types of textures in juvenile clasts, with different degrees of vesicularity and types and content of crystals. We propose that the eruption triggering mechanism was either exsolution of volatiles due to crystallization, or a small intrusion into the base of the magma chamber, without significant magma mixing or with a magma compositionally similar to that of the residing magma. In either case the triggering mechanism generated convection and sufficient overpressure to promote the first eruptive phase. The start of the eruption decompressed the chamber, promoting intense vesiculation of the remaining magma and an increase in eruption rate towards the end of the eruption.

Bayesian estimation of magma supply, storage, and eruption rates using a multiphysical volcano model: Kīlauea Volcano, 2000–2012

Estimating rates of magma supply to the world's volcanoes remains one of the most fundamental aims of volcanology. Yet, supply rates can be difficult to estimate even at well-monitored volcanoes, in part because observations are noisy and are usually considered independently rather than as part of a holistic system. In this work we demonstrate a technique for probabilistically estimating time-variable rates of magma supply to a volcano through probabilistic constraint on storage and eruption rates. This approach utilizes Bayesian joint inversion of diverse datasets using predictions from a multiphysical volcano model, and independent prior information derived from previous geophysical, geochemical, and geological studies. The solution to the inverse problem takes the form of a probability density function which takes into account uncertainties in observations and prior information, and which we sample using a Markov chain Monte Carlo algorithm. Applying the technique to Kīlauea Volcano, we develop a model which relates magma flow rates with deformation of the volcano's surface, sulfur dioxide emission rates, lava flow field volumes, and composition of the volcano's basaltic magma. This model accounts for effects and processes mostly neglected in previous supply rate estimates at Kīlauea, including magma compressibility, loss of sulfur to the hydrothermal system, and potential magma storage in the volcano's deep rift zones. We jointly invert data and prior information to estimate rates of supply, storage, and eruption during three recent quasi-steady-state periods at the volcano. Results shed new light on the time-variability of magma supply to Kīlauea, which we find to have increased by 35–100% between 2001 and 2006 (from 0.11–0.17 to 0.18–0.28 km 3 /yr), before subsequently decreasing to 0.08–0.12 km 3 /yr by 2012. Changes in supply rate directly impact hazard at the volcano, and were largely responsible for an increase in eruption rate of 60–150% between 2001 and 2006, and subsequent decline by as much as 60% by 2012. We also demonstrate the occurrence of temporal changes in the proportion of Kīlauea's magma supply that is stored versus erupted, with the supply “surge” in 2006 associated with increased accumulation of magma at the summit. Finally, we are able to place some constraints on sulfur concentrations in Kīlauea magma and the scrubbing of sulfur by the volcano's hydrothermal system. Multiphysical, Bayesian constraint on magma flow rates may be used to monitor evolving volcanic hazard not just at Kīlauea but at other volcanoes around the world. • A model of Kilauea Volcano is developed which predicts diverse observations. • Bayes' Theorem relates model, data, and independent prior information. • Probabilistic rates of magma supply, storage, and eruption are resolved. • Kilauea's magma supply has waxed and waned from 2000 to 2012. • Changes in supply control, in part, eruptive hazard at the volcano.

Intraplate volcanism influenced by distal subduction tectonics at Jeju Island, Republic of Korea

The drivers behind the inception of, and the variable, pulsatory eruption rates at distributed intraplate volcanic fields are not well understood. Such broad areas of monogenetic volcanism cover vast areas of the world and are often heavily populated. Reliable models to unravel their behaviour require robust spatio-temporal frameworks within the fields, but an analysis of the potential proximal and distal regional volcano-tectonic processes is also needed. Jeju Island (Republic of Korea) is a volcanic field that has been extensively drilled and dated. It is also located near one of the world’s best-studied tectonic plate boundaries: the subduction zone in southwestern Japan, which generates the Ryukyu and SW Japan arcs. A new set of 40Ar/39Ar ages collected from cores penetrating the entire Jeju eruptive pile, along with geochemical information, is used to construct a temporal and volumetric model for the volcano’s growth. The overall pattern indicates inception of volcanism at ~1.7 Ma, with an initial 1.2 Myr of low-rate activity, followed by over an order of magnitude rise over the last 0.5 Myr. The magma flux at Jeju correlates well with increased extension rates in the arc/backarc region. In particular, we infer that the increased trenchward mantle flow, caused by the greater rollback of the Philippine Sea Plate, activated pre-existing shear weaknesses in the mantle beneath Jeju, resulting in mantle upwelling and decompression melting that caused a change in compositions and an increase in eruption rates at Jeju. Thus, the volcanic activity of an intraplate field system can be modulated by regional subduction processes occurring more than 650 km away. This model may explain the frequent observation of pulsatory behaviour seen in many monogenetic volcanic fields worldwide that lie within 1,000 km of subduction zones.

Consequences of volcano sector collapse on magmatic storage zones: Insights from numerical modeling

Major volcano flank collapses strongly affect the underlying magmatic plumbing system. Here, we consider the magma storage zone as a liquid pocket embedded in an elastic medium, and we perform numerical simulations in two-dimensional axisymmetric geometry as well as in three dimensions in order to evaluate the consequences of a major collapse event. We quantify the pressure decrease induced within and around a magma reservoir by a volcano flank collapse. This pressure reduction is expected to favor replenishment with less evolved magma from deeper sources. We also estimate the impact of the magma pressure decrease, together with the stress field variations around the reservoir, on the eruptive event associated with the edifice failure. We show that, for a given magma reservoir geometry, the collapse of a large strato-volcano tends to reduce the volume of the simultaneous eruption; destabilization of large edifices may even suppress magma emission, resulting in phreatic eruptions instead. This effect is greater for shallow reservoirs, and is more pronounced for spherical reservoirs than for vertically-elongated ones. It is reduced for compressible magmas containing a large amount of volatiles. Over a longer time scale, the modification of pressure conditions for dyke initiation at the chamber wall may also explain an increase in eruption rate as well as an apparent change of magma storage location.

Morfologia e padrões petrográficos dos derrames pahoehoe e'a'ā da Formação Serra Geral na Sinclinal de Torres (Rio Grande do Sul)

The Serra Geral Formation volcanic sequence in Torres Syncline (Rio Grande do Sul state, Brazil) may be divided into main valley, intermediate zone, and southern hinge. The first volcanic episode along the syncline is characterized by low eruption rates ( ; 5 - 10 m³/s). The formation of 'a'ā flows occurred on a plain relief. Pahoehoe and 'a'ā flows have similar chemistry, and the difference in the flow type is related to an increase in eruption rates. The 'a'ā lavas are plagioclase and clinopyroxene phyric, or glomeroporphyritic. All present an intergranular or intersertal microcrystalline groundmass of plagioclase, clinopyroxene, and opaque minerals (<< 0.1 mm in diameter). The pahoehoe lavas differ from the 'a'ā ones in that they have a coarser-grained microcrystalline groundmass. The pahoehoe flows are microcrystalline with glomeroporphyritic and diktytaxitic textures and a plagioclase-poor matrix when compared to 'a'ā lava flows. The higher content of microlites in the 'a'ā flows is attributed to undercooling, higher rate of eruption, and degassing before and during emplacement. When it comes to regional stratigraphic correlation between the Serra Geral Formation flows, the morphological type of the lavas should be taken into account since 'a'ā flows, unlike pahoehoe, do not reach longer distances from the source.

Increase of MT1-MMP, TIMP-2 and Ki-67 proteins in the odontogenic region of the rat incisor post-shortening procedure

MT1-MMP and TIMP-2 are well known for their roles in remodelling of extracellular matrix components. However, reports are emerging on the involvement of these molecules in cell kinetics. In the rat incisor tooth, a shortening treatment increases the eruption and cell proliferation rates. However, the role of MT1-MMP and TIMP-2 proteins in these processes is still to be evaluated. Male Wistar rats were divided in two groups. In the normofunctional group (NF) the lower teeth of the rats remained in a normal eruption process. In the hypofunctional group (HP) rats their lower left incisor tooth was shortened every 2days during 12days. The eruption rate was estimated during the shortening period and MT1-MMP, TIMP-2 and Ki-67 protein expression from the odontogenic region was measured after the treatment. In HP groups an increase in eruption rate, and in MT1-MMP/TIMP-2 and Ki-67 expression were observed. We conclude that there is a relationship between the increase in eruption rate, and in levels of MT1-MMP, TIMP-2 and Ki-67 in the HP group. This suggests that MT1-MMP and TIMP-2 may have some role in cell proliferation during the eruption of the rat incisor tooth.

The influence of great earthquakes on volcanic eruption rate along the Chilean subduction zone

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.

The link between volcanism and deglaciation in Iceland

Temporal variation in the eruption rate and lava composition in the rift zones of Iceland is associated with deglaciation. Average eruption rates after the end of the last glacial period, ∼12 kyr BP, were up to 100 times higher than those from both the glacial period and recent times (&lt;5 kyr BP). This peak in volcanic activity finished less than 2 kyr after the end of deglaciation. New geochemical data from ∼80 basalt and picrite samples from the Theistareykir and Krafla volcanic systems show that there is a temporal variation in both the major and trace element composition of the eruptions. Early postglacial eruptions show a greater range in MgO contents than eruptions from other times, and at a fixed MgO content, the concentration of incompatible elements in subglacial eruptions is higher than that in early postglacial eruptions. Recent eruptions from the Krafla system have similar compositions to subglacial eruptions. The high eruption rates and low rare earth element (REE) concentrations in the lava from early postglacial times can be accounted for by increased melt generation rates in the shallow mantle caused by unloading of an ice sheet. Magma chamber processes such as crystallization and assimilation can produce the temporal variation in REE contents if garnet is present. However, garnet is not observed as a phenocryst or xenocryst phase and is not required to match the variation in major element contents observed at Krafla and Theistareykir. If the increase in eruption rates reflects increased melt production rates in the mantle, then the relative timing of deglaciation and the burst in eruption rates can be used to estimate the rate of melt transport in the mantle. The observed duration of enhanced eruption rates after deglaciation can be reproduced if the vertical melt extraction velocity is &gt;50 m yr−1.

Textural constraints on effusive silicic volcanism: Beyond the permeable foam model

Transitions between explosive and effusive phases of silicic volcanic eruptions have been related either to stratification of volatiles in the source magma body or to the loss of volatiles through the permeable host rock of the conduit. One way to distinguish between these two models is to map and analyze the vesicular and glassy textures found in silicic lava flows. In this paper we present textural observations and isotopic evidence from active and Recent silicic lava flows which show that at least some vesiculation occurs during surface advance of extrusions, after magma has reached the earth's surface. This view is in contrast to the widely promoted “permeable foam” model, which states that all volatiles escape during ascent of the magma, and that all dense glassy material in lava flows forms from the collapse of pumiceous lava, i.e., that silicic lavas emerge as highly inflated foam flows. Such interpretations which claim that silicic lavas are completely degassed upon extrusion, and that all degassing must take place on the time scale of the eruption, neglect several important pieces of evidence, including the presence of obsidian in extremely small domes, and of vesicular zones in the interiors of silicic flows; the copious loss of volatiles through eruption plumes between eruptive phases; and direct observations of surface vesiculation during growth of the Mount St. Helens lava dome. The permeable foam model also implies the unlikely requirement that explosive‐to‐effusive transitions be associated with an increase in eruption rate. We present a more comprehensive model for the emplacement of silicic extrusions that allows for early gas loss during ascent, as well as late‐stage vesiculation. We then discuss how the redistribution of volatiles during surface flow can increase explosive hazards from silicic lavas days, weeks, or months after the lava emerges from the vent.

Age of tilted reefs, Hawaii

Submerged carbonate reefs are preserved as a series of submarine terraces between Molokai and Hawaii along a 200‐km span of the southeastern Hawaiian Ridge. Limestones from two of the terraces have been sampled from submersibles and dated radiometrically at 13 and 120 ka. Recognition that the terraces are tilted permits assignment of about a dozen terraces from 150 to 1300 m depth to eight general reef platforms. These reefs were drowned by the combined effects of island subsidence and sea level rise at the end of successive glacial stages from 13 to 647 ka. The platforms are tilted 5 m/km southeast toward the locus of volcanic loading centered on the island of Hawaii. The end of the active period of volcanic shield building is represented on each nonactive volcano by a submerged change in slope. Dating of this slope change by reference to the dated reefs provides independent evidence that shield building ended at about the same time that the volcano changed from eruption of tholeiitic to alkalic basalt. The variation in depth of the dated tilted reefs along the ridge indicates that the end of subsidence follows the end of shield building by about one half million years. The present northwest margin of major subsidence probably crosses southeast Maui. During the last half million years the rate of southeast migration of the beginning of both subsidence and of tholeiitic volcanism does not appear to have increased. However, the rate of southeast migration of the end of both subsidence and of tholeiitic volcanism has apparently increased. This shortening of the life history of the younger volcanoes implies an increase in eruption rates.

Interactions between thyroxine, hydrocortisone and cyclophosphamide in their effects on the eruption of the rat mandibular incisor

The effects on the unimpeded eruption rates of the rat mandibular incisor of daily doses of thyroxine (0.5mg/kg) and hydrocortisone (12.5 mg/kg) and of a single injection of cyclophosphamide (40 mg/kg), either alone or in combination, were studied over ~15 days. Both the thyroxine and hydrocortisone alone produced increases in eruption, whereas a decrease was recorded with cyclophosphamide alone. When thyroxine was combined with hydrocortisone, the increase in eruption rate was greater than that with thyroxine or hydrocortisone alone. When cyclophosphamide was combined with hydrocortisone, there was no difference compared with cyclophosphamide alone. These results obtained with drug combinations are consistent with eruption having a multifactorial basis.

The Effect of a Magnesium Deficient Diet and Cortisone on the Growth of the Rat Incisor

Incisors of Mg-deficient rats showed a marked inhibition of eruption and a decrease in mitoses of apical tissues. Cortisone administration resulted in some increase in eruption rate and cell division though these remained below the values of Mg-supplemented controls. An improvement in gross condition and a less severe histopathology of incisor tissues were also observed in cortisone-treated rats.