scholarly journals Basaltic feeder dykes in rift zones: geometry, emplacement, and effusion rates

2012 ◽  
Vol 12 (12) ◽  
pp. 3683-3700 ◽  
Author(s):  
I. Galindo ◽  
A. Gudmundsson
Keyword(s):  
Volcanic Hazards ◽  
Effusion Rate ◽  
Eruptive Fissure ◽  
Existing Structures ◽  
Internal Structures ◽  
Effusion Rates ◽  
Rift Zones ◽  
Prolate Ellipsoidal ◽  
Initial Peak ◽  
Eruptive Fissures

Abstract. Most volcanic hazards depend on an injected dyke reaching the surface to form a feeder. Assessing the volcanic hazard in an area is thus related to understanding the condition for the formation of a feeder dyke in that area. For this latter, we need good field data on feeder dykes, their geometries, internal structures, and other characteristics that distinguish them from non-feeders. Unfortunately, feeder dykes are rarely observed, partly because they are commonly covered by their own products. For this reason, outcrops are scarce and usually restricted to cliffs, ravines, and man-made outcrops. Here we report the results of a study of feeder dykes in Tenerife (Canary Islands, Spain) and Iceland, focusing on their field characteristics and how their propagation is affected by existing structures. Although Holocene fissure eruptions have been common in both islands, only eleven basaltic feeder dykes have been identified: eight in Tenerife and three in Iceland. They are all well preserved and the relation with the eruptive fissure and/or the deposits is well exposed. While the eruptive fissures are generally longer in Iceland than in Tenerife, their feeders show many similarities, the main ones being that the feeder dykes (1) are generally sheet-shaped; (2) are segmented (as are the associated volcanic fissures); (3) normally contain elongated (prolate ellipsoidal) cavities in their central, topmost parts, that is, 2–3 m below the surface (with solidified magma drops on the cavity walls); (4) contain vesicles which increase in size and number close to the surface; (5) sometimes inject oblique dyke fingers into the planes of existing faults that cross the dyke paths; and (6) may reactivate, that is, trigger slip on existing faults. We analyse theoretically the feeder dyke of the 1991 Hekla eruption in Iceland. Our results indicate that during the initial peak in the effusion rate the opening (aperture) of the feeder dyke was as wide as 0.77 m, but quickly decreased to about 0.56 m. During the subsequent decline in the effusion rate to a minimum, the aperture decreased to about 0.19 m. At a later abrupt increase in the effusion rate, the feeder-dyke opening may have increased to about 0.34 m, and then decreased again as the effusion rate gradually declined during the end stages of the eruption. These thickness estimates fit well with those of many feeders in Iceland and Tenerife, and with the general dyke thickness within fossil central volcanoes in Iceland.

Ground deformation associated with the August 2019 eruption of Piton de la Fournaise (La Réunion Island) inferred from DInSAR measurements

2020 ◽  
Author(s):  
Vincenzo De Novellis ◽  
Francesco Casu ◽  
Claudio De Luca ◽  
Mariarosaria Manzo ◽  
Fernando Monterroso ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Coseismic Deformation ◽  
Southeastern Part ◽  
Eruptive Fissure ◽  
Piton De La Fournaise ◽  
Synthetic Aperture Radar Interferometry ◽  
Small Baseline Subset ◽  
Small Baseline ◽  
Deformation Patterns ◽  
Eruptive Fissures

<p>Piton de la Fournaise volcano forms the southeastern part of La Réunion, an oceanic basaltic island in the southernmost part of Mascarene Basin (Indian Ocean). Five eruptions occurred at Piton in 2019, accompanied by seismic activity, lava flow, and lava fountaining. Here below, we focus on the fourth eruption occurred between August 11 and 15 on the southern-southeastern flank of the volcano, inside the Enclos Fouqué caldera. This eruption was characterized by the opening of two eruptive fissures. We retrieve the surface deformations induced by the eruptive activity through space-borne Differential Synthetic Aperture Radar Interferometry (DInSAR) measurements. First, we generated the coseismic deformation maps by applying the DInSAR technique to SAR data collected along ascending and descending orbits by the Sentinel-1 constellation of the European Copernicus Programme. The DInSAR technique allows us to analyze the deformation patterns caused by the 11 August 2019 eruption. We also retrieved the pre-eruptive deformation through the Small BAseline Subset (SBAS) DInSAR approach. Then, we modelled the DInSAR displacements to constrain the geometry and characteristics of the eruptive source. The modelling results suggest that the observed deformation can be attributed to the interaction between a shallow magma reservoir located at ~1.5-2 km depth below the summit, and the intrusion of a dike feeding the eruptive fissure inside the Enclos Fouqué caldera.</p><p><em>This work is supported by: the 2019-2021 IREA-CNR and Italian Civil Protection Department agreement; the EPOS-SP project (GA 871121); and the I-AMICA (PONa3_00363) project.</em></p>

scholarly journals Will subglacial rhyolite eruptions be explosive or intrusive? Some insights from analytical models

2007 ◽  
Vol 45 ◽  
pp. 87-94 ◽  
Author(s):  
H. Tuffen ◽  
D.W. McGarvie ◽  
J.S. Gilbert
Keyword(s):  
Analytical Models ◽  
Explosive Eruptions ◽  
Effusion Rate ◽  
Cavity Pressure ◽  
Eruption Style ◽  
Water Interaction ◽  
Subglacial Eruptions ◽  
Effusion Rates

AbstractSimple analytical models of subglacial eruptions are presented, which simulate evolving subglacial cavities and volcanic edifices during rhyolitic eruptions beneath temperate glaciers. They show that the relative sizes of cavity and edifice may strongly influence the eruption mechanisms. Intrusive eruptions will occur if the edifice fills the cavity, with rising magma quenched within the edifice and slow melting of ice. Explosive magma–water interaction may occur if a water- or steam-filled gap develops above the edifice. Meltwater is assumed to drain away continuously, but any gap above the edifice will be filled by meltwater or steam. Ductile roof closure will occur if the glacier weight exceeds the cavity pressure and is modelled here using Nye’s law. The results show that the effusion rate is an important control on the eruption style, with explosive eruptions favoured by large effusion rates. The models are used to explain contrasting eruption mechanisms during various Quaternary subglacial rhyolite eruptions at Torfajökull, Iceland. Although the models are simplistic, they are first attempts to unravel the complex feedbacks between subglacial eruption mechanisms and glacier response that can lead to a variety of eruptive scenarios and associated hazards.

Periodic dike intrusions at Kīlauea volcano, Hawaiʻi

Geology ◽  
2020 ◽  
Author(s):  
Emily K. Montgomery-Brown ◽  
Asta Miklius
Keyword(s):  
Rift Zone ◽  
Volcanic Hazards ◽  
Kilauea Volcano ◽  
Magma Supply ◽  
Kīlauea Volcano ◽  
Recurrence Intervals ◽  
Rift Zones ◽  
Intrusive Activity

Forecasting heightened magmatic activity is key to assessing and mitigating global volcanic hazards, including eruptions from lateral rift zones at basaltic volcanoes. At Kīlauea volcano, Hawaiʻi (United States), planar dikes intrude its east rift zone (ERZ) and repeatedly affect the same segments. Here we show that Kīlauea’s upper and middle ERZ dikes in the last four decades intruded at regular intervals of ~8 or ~14 yr. Segments with shorter recurrence intervals are adjacent to faster-moving parts of the flank, and ~1–5 MPa of tension accumulates from flank spreading in the time between dike events. Intrusion frequency was neither advanced nor delayed during magma supply variations, supporting the role of long-term flank motion on the timing of dike intrusions. Although fewer historical dikes have occurred near the 2018 CE eruption site in the lower ERZ and the adjacent slowly sliding lower eastern flank, similar tension accumulated between the 1955 and 2018 eruptions. Regular dike intrusion recurrence intervals indicate the importance of including both extrusive and (commonly neglected) intrusive activity in eruption hazard analyses.

scholarly journals The VEI 2 Christmas 2018 Etna Eruption: A Small But Intense Eruptive Event or the Starting Phase of a Larger One?

2020 ◽  
Vol 12 (6) ◽  
pp. 905 ◽  
Author(s):  
Sonia Calvari ◽  
Giuseppe Bilotta ◽  
Alessandro Bonaccorso ◽  
Tommaso Caltabiano ◽  
Annalisa Cappello ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Volcanic Hazards ◽  
Flank Eruption ◽  
Eruptive Fissure ◽  
So2 Flux ◽  
Sequence Of Events ◽  
Shallow Earthquakes ◽  
Lava Fountains ◽  
Remote Sensing Techniques ◽  
Opening Stage

The Etna flank eruption that started on 24 December 2018 lasted a few days and involved the opening of an eruptive fissure, accompanied by a seismic swarm and shallow earthquakes, significant SO2 flux release, and by large and widespread ground deformation, especially on the eastern flank of the volcano. Lava fountains and ash plumes from the uppermost eruptive fissure accompanied the opening stage, causing disruption to Catania International Airport, and were followed by a quiet lava effusion within the barren Valle del Bove depression until 27 December. This was the first flank eruption to occur at Etna in the last decade, during which eruptive activity was confined to the summit craters and resulted in lava fountains and lava flow output from the crater rims. In this paper, we used ground and satellite remote sensing techniques to describe the sequence of events, quantify the erupted volumes of lava, gas, and tephra, and assess volcanic hazards.

Lava flow hazard of the 2018 Etna eruption: What happened and what could happen

2021 ◽  
Author(s):  
Giuseppe Bilotta ◽  
Sonia Calvari ◽  
Annalisa Cappello ◽  
Claudia Corradino ◽  
Ciro Del Negro ◽  
...  
Keyword(s):  
Lava Flow ◽  
Thermal Flux ◽  
Satellite Monitoring ◽  
Effusion Rate ◽  
Eruptive Fissure ◽  
Infrared Imager ◽  
Significant Damage ◽  
Lava Flow Field ◽  
Western Wall ◽  
Infrared Data

<p>On 24 December 2018 a flank eruption started on Etna from an eruptive fissure opened on the eastern side of the New Southeast Crater (NCSE) at about 3,100 m asl, which in few minutes, propagated to the south-east, overcoming the edge of the western wall of the Valle del Bove (VdB), reaching an altitude of 2,400 m asl and a total length of about 2 km. The eruption, which lasted only three days, produced lava flows from different vents along the eruptive fissure that reached a distance of about 4.2 km and covered an area of about 1 km2. The satellite monitoring of the 2018 Etna eruption was performed using the HOTSAT system using mid and thermal infrared data acquired by the Spinning Enhanced Visible and InfraRed Imager (SEVIRI), which provided minimum and maximum estimates for the lava thermal flux, the effusion rate and the lava volume. The SEVIRI-derived effusion rate estimates were used as input of the MAGFLOW model to simulate the actual lava flow field, obtaining a very good fit. We also simulated different eruptive scenarios assuming the lava emission wouldn’t run out in only three days to forecast if, when and how the lava flow could reach the inhabited areas, causing possible significant damage. </p>

scholarly journals NICE thromboprophylaxis guidelines are not associated with increased pericardial effusion after surgery of the proximal thoracic aorta

2013 ◽  
Vol 95 (6) ◽  
pp. 433-436 ◽  
Author(s):  
IA Rahman ◽  
A Hussain ◽  
A Davies ◽  
AJ Bryan
Keyword(s):  
Pericardial Effusion ◽  
Dose Group ◽  
Low Dose ◽  
Aortic Surgery ◽  
Clinical Excellence ◽  
High Dose ◽  
Effusion Rate ◽  
Aortic Cross Clamp Time ◽  
Effusion Rates ◽  
One Year

Introduction In 2010 the National Institute for Health and Clinical Excellence (NICE) released guidelines on venous thromboembolism. Strategy focused on risk assessment, antiembolic stockings, sequential compression devices, subcutaneous high dose enoxaparin (40mg), early mobilisation and hydration. The 40mg enoxaparin dose over the previous 20mg regimen was worrisome, and its effect on pericardial effusion rates and mortality in proximal aortic surgery was investigated. Methods Proximal aortic reconstructions performed between December 2008 and April 2011 were identified from prospectively collected data in a tertiary centre database. Retrospective analysis of patient notes was performed. Proximal aortic surgery patients were categorised as low dose (20mg) enoxaparin and high dose (40mg) enoxaparin, and compared for confounding variables. In-hospital, early and one-year readmission rates for pericardial effusion were ascertained from echocardiography reports. The primary outcome was total pericardial effusion rate. Secondary outcomes consisted of 30-day and 1-year mortality. Results A total of 198 patients underwent proximal thoracic aortic surgery. Nine patients were excluded due to early postoperative death (n=5) and missing patient records (n=4). This left 189 cases for analysis. There were 93 patients in the low dose group and 96 in the high dose group. Groups were comparable for age, cardiopulmonary bypass time, aortic cross-clamp time, postoperative warfarin and antiplatelet agents. Pericardial effusion rates up to one year were comparable (low dose 19% vs high dose 21%). Thirty-day mortality was lower in the low dose group (0 vs 3 deaths). There were four deaths up to one year but these were not attributable to increased enoxaparin. Conclusions Increased perioperative thromboprophylaxis dosage does not increase pericardial effusion rates or mortality in proximal aortic surgery.

scholarly journals Linking lava morphologies to effusion rates for the 2014–2015 Holuhraun lava flow field, Iceland

Geology ◽  
2021 ◽  
Author(s):  
Joana R.C. Voigt ◽  
Christopher W. Hamilton ◽  
Gregor Steinbrügge ◽  
Ármann Höskuldsson ◽  
Ingibjörg Jónsdottir ◽  
...  
Keyword(s):  
Flow Field ◽  
Lava Flow ◽  
Discharge Rate ◽  
Transport Processes ◽  
Data Sets ◽  
Effusion Rate ◽  
Lava Flow Field ◽  
Geomorphological Map ◽  
Effusion Rates ◽  
Lava Emplacement

Determining the parameters that control fissure-fed lava morphologies is critical for reconstructing the complex emplacement histories of eruptions on Earth and other planetary bodies. We used a geomorphological map of the 2014–2015 Holuhraun lava flow field, in combination with new constraints on lava emplacement chronology and two independently derived time-averaged discharge rate (TADR) data sets, to analyze correlations between lava morphology and effusion rate. Results show that lava morphologies are dominantly controlled by effusion rate at the vent during the early phases of the eruption and by lava transport processes as the system evolves. Initially, TADR and its variance, which reflect pulsation in the lava supply rate from the vent, directly affect lava emplacement styles. However, as the eruption progresses, the lava transport system exerts a stronger control with channels and ponds that can either dampen variation in local effusion rate or create surges during sudden drainage events. The Holuhraun eruption predominantly produced rubbly lava in its earlier eruption phases and transitioned into the production of spiny lava toward the end of the eruption. However, a drop of TADR during the first phase of the eruption correlates with a decrease in rubbly lava formation and an increase in spiny lava production. This suggests that a change in effusion rate caused the observed transition in lava type. Our findings show that rubbly lava is formed under relatively high local effusion rates with pulsating supply conditions, whereas spiny lava is formed under lower local effusion rates and steadier supply.

scholarly journals The 1974 West Flank Eruption of Mount Etna: A Data-Driven Model for a Low Elevation Effusive Event

2020 ◽  
Vol 8 ◽  
Author(s):  
Charline Lormand ◽  
Andrew J. L. Harris ◽  
Magdalena Oryaëlle Chevrel ◽  
Sonia Calvari ◽  
Lucia Gurioli ◽  
...  
Keyword(s):  
Phase I ◽  
Lava Flow ◽  
Phase Ii ◽  
Flow System ◽  
Flow Fields ◽  
Mount Etna ◽  
Effusion Rate ◽  
Flow Units ◽  
Levee Failure ◽  
Effusion Rates

Low elevation flank eruptions represent highly hazardous events due to their location near, or in, communities. Their potentially high effusion rates can feed fast moving lava flows that enter populated areas with little time for warning or evacuation, as was the case at Nyiragongo in 1977. The January–March 1974 eruption on the western flank of Mount Etna, Italy, was a low elevation effusive event, but with low effusion rates. It consisted of two eruptive phases, separated by 23 days of quiescence, and produced two lava flow fields. We describe the different properties of the two lava flow fields through structural and morphological analyses using UAV-based photogrammetry, plus textural and rheological analyses of samples. Phase I produced lower density (∼2,210 kg m−3) and crystallinity (∼37%) lavas at higher eruption temperatures (∼1,080°C), forming thinner (2–3 m) flow units with less-well-developed channels than Phase II. Although Phase II involved an identical source magma, it had higher densities (∼2,425 kg m−3) and crystallinities (∼40%), and lower eruption temperatures (∼1,030°C), forming thicker (5 m) flow units with well-formed channels. These contrasting properties were associated with distinct rheologies, Phase I lavas having lower viscosities (∼103 Pa s) than Phase II (∼105 Pa s). Effusion rates were higher during Phase I (≥5 m3/s), but the episodic, short-lived nature of each lava flow emplacement event meant that flows were volume-limited and short (≤1.5 km). Phase II effusion rates were lower (≤4 m3/s), but sustained effusion led to flow units that could still extend 1.3 km, although volume limits resulted from levee failure and flow avulsion to form new channels high in the lava flow system. We present a petrologically-based model whereby a similar magma fed both phases, but slower ascent during Phase II may have led to greater degrees of degassing resulting in higher cooling-induced densities and crystallinities, as well as lower temperatures. We thus define a low effusion rate end-member scenario for low elevation effusive events, revealing that such events are not necessarily of high effusion rate and velocity, as in the catastrophic event scenarios of Etna 1669 or Kilauea 2018.

Lava flow growth inferred from morphometric parameters: a case study of Citlaltépetl volcano, Mexico

1997 ◽  
Vol 134 (2) ◽  
pp. 151-162 ◽  
Author(s):  
GERARDO CARRASCO-NÚÑEZ
Keyword(s):  
Lava Flow ◽  
Morphometric Parameters ◽  
Effusion Rate ◽  
Cooling Method ◽  
Multiple Flows ◽  
Lava Type ◽  
Effusion Rates ◽  
The Relationship ◽  
Eruption Duration

Recent (Quaternary) lava fields, such as those of Citlaltépetl (Pico de Orizaba) volcano in Mexico, are excellent places to obtain precise measurements of flow-field dimensions that can be used to estimate volume, eruption duration and effusion rates. The relationship between these parameters and the influence of some other interrelated features such as lava composition, superficial structures and lava type are important tools that can help to infer conditions when the lavas were active and thus improve understanding of how flow fields grow. The Holocene lavas of Citlaltépetl volcano are homogeneous in composition (dacites) and are generally blocky with well-developed levees. The eruption duration obtained for the Citlaltépetl lavas by a method proposed by C. Kilburn and R. Lopes presents a good correlation with the different lava types morphologically classified here. Results from that method compare favourably with the inferred effusion rates estimated by an empirical cooling method (Graetz). The lavas show different behaviour, mainly controlled by fluctuations in the effusion rate that promote changes from single- to multiple-flow style. The maximum distance achieved by a flow is directly proportional to the effusion rate in Citlaltépetl lavas, but it is always lower for multiple flows, independent of the volume of erupted lava. Observations of Citlaltépetl lavas can be used to understand how lava flow growth occurs on other volcanoes.

Sign in / Sign up

Export Citation Format

Share Document