Shear localisation, strain partitioning and frictional melting in a debris avalanche generated by volcanic flank collapse

Hydrothermal alteration can progressively weaken volcanic flanks, leading to collapses and mass flows with potential hazards affecting communities and infrastructure many kilometres from the collapse source. Through a combination of geomagnetic and hyperspectral remote sensing, with field and laboratory measurements, we have developed an approach to assess and forecast these catastrophic hazards. Inversion of aerial geo-magnetic data is used to identify the subsurface structure and volume of weak (nominally altered) and strong (nominally unaltered) portions of the volcanic edifice of Mt. Ruapehu, New Zealand. Airborne hyperspectral imagery is used to classify the surface expression of hydrothermal alteration, which is combined with laboratory geotechnical measurements of field samples to estimate the strength of identified features. This data is essential to reducing the uncertainty in identifying flank collapse source areas through three-dimensional limit equilibrium modelling.However, the range of potential collapse volumes, locations and triggering mechanisms still presents significant difficulties in forecasting the potential impacts of slope failures. Numerical mass flow models can be used to simulate debris avalanches, but it is infeasible to simulate all potential collapse scenarios to estimate the hazard. To ease the computational burden, we have developed a methodology that uses a reduced subset of potential slope failures through dimensional reduction and space-filling sampling techniques. Using debris avalanche simulations of this subset, a comprehensive mapping of debris flow impacts across the entire input space can be developed using statistical techniques. This mapping provides an efficient mechanism for understanding flank collapse hazards across a large spectrum of potential scenarios. This presentation will outline our framework for assessing and forecasting debris avalanche hazards through the integration of remote sensing surveys with geotechnical measurements.

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Syn-Eruptive Lateral Collapse of Monogenetic Volcanoes: The Case of Mazo Volcano from the Timanfaya Eruption (Lanzarote, Canary Islands)

10.5772/intechopen.93882 ◽

2020 ◽

Author(s):

Carmen Romero ◽

Inés Galindo ◽

Nieves Sánchez ◽

Esther Martín-González ◽

Juana Vegas

Keyword(s):

Canary Islands ◽

Great Part ◽

Volcanic Hazards ◽

Debris Avalanche ◽

Mitigation Strategies ◽

Morphological Data ◽

Flank Collapse ◽

Tectonic Process ◽

Eruptive Style ◽

History Of

The evolution of complex volcanic structures usually includes the occurrence of flank collapse events. Monogenetic cones, however, are more stable edifices with minor rafting processes that remove part of the cone slopes. We present the eruptive history of Mazo volcano (Lanzarote, Canary Islands), including the first detailed description of a syn-eruptive debris avalanche affecting a volcanic monogenetic edifice. The study and characterization, through new geological and morphological data and the analysis of a great number of documentary data, have made it possible to reinterpret this volcano and assign it to the Timanfaya eruption (1730–1736). The eruptive style evolved from Hawaiian to Strombolian until a flank collapse occurred, destroying a great part of the edifice, and forming a debris avalanche exhibiting all the features that define collapsing volcanic structures. The existence of blocks from the substrate suggests a volcano-tectonic process associated with a fracture acting simultaneously with the eruption. The sudden decompression caused a blast that produced pyroclasts that covered most of the island. This study forces to change the current low-hazard perception usually linked to monogenetic eruptions and provides a new eruptive scenario to be considered in volcanic hazards analysis and mitigation strategies development.

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Numerical simulation of the 30–45 ka debris avalanche flow of Montagne Pelée volcano, Martinique: from volcano flank collapse to submarine emplacement

Natural Hazards ◽

10.1007/s11069-017-2815-5 ◽

2017 ◽

Vol 87 (2) ◽

pp. 1189-1222 ◽

Cited By ~ 12

Author(s):

Morgane Brunet ◽

Laurent Moretti ◽

Anne Le Friant ◽

Anne Mangeney ◽

Enrique Domingo Fernández Nieto ◽

...

Keyword(s):

Numerical Simulation ◽

Debris Avalanche ◽

Flank Collapse ◽

Avalanche Flow

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Flank collapse at Mount Wrangell, Alaska, recorded by volcanic mass-flow deposits in the Copper River lowland

Canadian Journal of Earth Sciences ◽

10.1139/e02-032 ◽

2002 ◽

Vol 39 (8) ◽

pp. 1257-1279 ◽

Cited By ~ 16

Author(s):

Christopher F Waythomas ◽

Kristi L Wallace

Keyword(s):

Debris Flow ◽

Mass Flow ◽

Volcanic Rocks ◽

Debris Avalanche ◽

Sector Collapse ◽

Flow Forming ◽

Flank Collapse ◽

South Central ◽

Flow Deposit ◽

Facies Types

An areally extensive volcanic mass-flow deposit of Pleistocene age, known as the Chetaslina volcanic mass-flow deposit, is a prominent and visually striking deposit in the southeastern Copper River lowland of south-central Alaska. The mass-flow deposit consists of a diverse mixture of colorful, variably altered volcanic rocks, lahar deposits, glaciolacustrine diamicton, and till that record a major flank collapse on the southwest flank of Mount Wrangell. The deposit is well exposed near its presumed source, and thick, continuous, stratigraphic exposures have permitted us to study its sedimentary characteristics as a means of better understanding the origin, significance, and evolution of the deposit. Deposits of the Chetaslina volcanic mass flow in the Chetaslina River drainage are primary debris-avalanche deposits and consist of two principal facies types, a near-source block facies and a distal mixed facies. The block facies is composed entirely of block-supported, shattered and fractured blocks with individual blocks up to 40 m in diameter. The mixed facies consists of block-sized particles in a matrix of poorly sorted rock rubble, sand, and silt generated by the comminution of larger blocks. Deposits of the Chetaslina volcanic mass flow exposed along the Copper, Tonsina, and Chitina rivers are debris-flow deposits that evolved from the debris-avalanche component of the flow and from erosion and entrainment of local glacial and glaciolacustrine diamicton in the Copper River lowland. The debris-flow deposits were probably generated through mixing of the distal debris avalanche with the ancestral Copper River, or through breaching of a debris-avalanche dam across the ancestral river. The distribution of facies types and major-element chemistry of clasts in the deposit indicate that its source was an ancestral volcanic edifice, informally known as the Chetaslina vent, on the southwest side of Mount Wrangell. A major sector collapse of the Chetaslina vent initiated the Chetaslina volcanic mass flow forming a debris avalanche of about 4 km3 that subsequently transformed to a debris flow of unknown volume.

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Revisiting the tsunamigenic volcanic flank collapse of Fogo Island in the Cape Verdes, offshore West Africa

Geological Society London Special Publications ◽

10.1144/sp500-2019-187 ◽

2019 ◽

Vol 500 (1) ◽

pp. 13-26 ◽

Cited By ~ 1

Author(s):

Rachel Barrett ◽

Elodie Lebas ◽

Ricardo Ramalho ◽

Ingo Klaucke ◽

Steffen Kutterolf ◽

...

Keyword(s):

Large Scale ◽

Debris Avalanche ◽

Volcanic Material ◽

Flank Collapse ◽

Bathymetric Data ◽

Medium Resolution ◽

History Of ◽

Seafloor Sediments ◽

Multi Phase ◽

Mass Transport Deposits

AbstractVolcanic archipelagos are a source of numerous on- and offshore geohazards, including explosive eruptions and potentially tsunamigenic large-scale flank collapses. Fogo Island in the southern Cape Verdes is one of the most active volcanoes in the world, making it both prone to collapse (as evidenced by the c. 73 ka Monte Amarelo volcanic flank collapse), and a source of widely distributed tephra and volcanic material. The offshore distribution of the Monte Amarelo debris avalanche deposits and the surrounding volcaniclastic apron were previously mapped using only medium-resolution bathymetric data. Here, using recently acquired, higher-resolution acoustic data, we revisit Fogo's flank collapse and find evidence suggesting that the deposition of hummocky volcanic debris originating from the failed eastern flank most likely triggered the contemporaneous, multi-phase failure of pre-existing seafloor sediments. Additionally, we identify, for the first time, multiple mass-transport deposits in the southern part of the volcaniclastic apron of Fogo and Santiago based on the presence of acoustically chaotic deposits in parametric echo sounder data and volcaniclastic turbiditic sands in recovered cores. These preliminary findings indicate a long and complex history of instability on the southern slopes of Fogo and suggest that Fogo may have experienced multiple flank collapses.

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Modeling of partial dome collapse of La Soufrière of Guadeloupe volcano: implications for hazard assessment and monitoring

Scientific Reports ◽

10.1038/s41598-019-49507-0 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 7

Author(s):

Marc Peruzzetto ◽

Jean-Christophe Komorowski ◽

Anne Le Friant ◽

Marina Rosas-Carbajal ◽

Anne Mangeney ◽

...

Keyword(s):

Coulomb Friction ◽

Hazard Analysis ◽

Debris Avalanche ◽

Flank Collapse ◽

Barrier Effects ◽

History Of ◽

Assessment And Monitoring ◽

Coulomb Friction Law ◽

Dome Collapse ◽

Best Fit

Abstract Over the past 9,150 years, at least 9 flank collapses have been identified in the history of La Soufrière of Guadeloupe volcano. On account of the volcano’s current unrest, the possibility of such a flank collapse should not be dismissed in assessing hazards for future eruptive magmatic as well as non-magmatic scenarios. We combine morphological and geophysical data to identify seven unstable structures (volumes ranging from 1 × 106 m3 to 100 × 106 m3), including one that has a volume compatible with the last recorded flank collapse in 1530 CE. We model their dynamics and emplacement with the SHALTOP numerical model and a simple Coulomb friction law. The best-fit friction coefficient to reproduce the 1530 CE event is tan(7°) = 0.13, suggesting the transformation of the debris avalanche into a debris flow, which is confirmed by the texture of mapped deposits. Various friction angles are tested to investigate less water-rich and less mobile avalanches. The most densely populated areas of Saint-Claude and Basse-Terre, and an area of Gourbeyre south of the Palmiste ridge, are primarily exposed in the case of the more voluminous and mobile flank collapse scenarios considered. However, topography has a prominent role in controlling flow dynamics, with barrier effects and multiple channels. Classical mobility indicators, such as the Heim’s ratio, are thus not adequate for a comprehensive hazard analysis.

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Internal architecture of the two-fold nature Monte Amarelo volcanic flank-collapse deposit offshore Fogo Island in the southern Cape Verdean Archipelago

10.5194/egusphere-egu2020-19095 ◽

2020 ◽

Author(s):

Elodie Lebas ◽

Elisa Klein ◽

Rachel Barrett ◽

Ricardo Ramalho ◽

Katja Lindhorst ◽

...

Keyword(s):

Seismic Data ◽

Large Scale ◽

Distal Part ◽

Debris Avalanche ◽

Acoustic Energy ◽

Sidescan Sonar ◽

Cape Verdean ◽

Hazard Potential ◽

Flank Collapse ◽

Internal Architecture

Volcanic islands are the sites of some of the largest submarine landslides observed on Earth. Individual landslide deposits can contain several hundreds to few thousands of cubic kilometers of mobilized material and, therefore, represent significant hazards. They can generate destructive tsunamis which may have devastating impacts on coastal areas and populations. Hazard potential of volcanic flank-collapses is widely recognized, but the magnitude, and therefore the hazard potential of tsunamis triggered by such collapses have been much debated over the past decades. Hence, a better understanding and a full characterization of volcanic landslide deposits and emplacement dynamics is crucial. Fogo Island, situated in the southern part of the Cape Verdean Archipelago, is one of the most active oceanic intraplate volcanoes in the world. Fogo Volcano experienced a catastrophic flank-collapse event as witnessed by up-to-1 km high, eastward-opened horseshoe-shape depression. Tsunami deposits found on the nearby islands of Santiago and Maio indicate that the flank-collapse was tsunamigenic (Ramalho et al. 2015; Madeira et al. 2019). To better constrain the tsunamigenic hazard potential of this large, volcanic flank-collapse, we collected in 2019 a dense network of marine geophysical datasets offshore Fogo. Our dataset includes high-resolution multi-beam swath bathymetry, parametric sediment echo-sounder, multi-channel seismic reflection, sidescan sonar data and sediment gravity cores. Here, we present the key results of the seismic data. We show &#8211; for the first time &#8211; the internal architecture of the Monte Amarelo flank-collapse deposit in unprecedented detail. Our data reveal a two-fold nature of the deposit with hummocky terrains in the proximal area &#8211; typical of blocky debris avalanche deposits &#8211; and finer-grained, acoustically transparent deposits in the southern distal part. Our observations support recently-proposed failure models, where the loading of seafloor sediment by volcanic debris avalanche deposits triggered sediment destabilization and progressive downslope-propagating failure along a d&#233;collement surface (Le Friant et al. 2015, 2020). The basal surface of the Monte Amarelo deposits along with a series of strong internal reflections have also been captured in the seismic data, both in the proximal and distal part. This suggests a multi-phase event in the emplacement of the Monte Amarelo deposit offshore and allows us to reassess the volume of failed and remobilized material. Such details are particularly unusual on submarine volcanic flanks, as it is rather difficult to image the base of debris avalanche deposits due to their hummocky nature that instantly diffract/scatter the acoustic energy. This makes Fogo&#8217;s Monte Amarelo volcanic flank-collapse deposit a perfect study case to investigate the emplacement dynamics of large-scale, volcanic flank collapses and better constrain their tsunamigenic hazard potential.

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STRUCTURE, KINEMATICS, AND STRAIN PARTITIONING OF AN EXHUMED HIGH PRESSURE TERRAIN: THE ROAN WINDOW, NORWAY

10.1130/abs/2019am-338178 ◽

2019 ◽

Author(s):

Christine E. Newville ◽

◽

Christian Teyssier ◽

Donna L. Whitney ◽

Hannah J. Blatchford

Keyword(s):

High Pressure ◽

Strain Partitioning

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Impact of Coseismic Frictional Melting on Particle Size, Shape Distribution and Chemistry of Experimentally-Generated Pseudotachylite

Frontiers in Earth Science ◽

10.3389/feart.2020.596116 ◽

2020 ◽

Vol 8 ◽

Author(s):

Leny Montheil ◽

Virginia G. Toy ◽

James M. Scott ◽

Thomas M. Mitchell ◽

David P. Dobson

Keyword(s):

Particle Size ◽

Host Rock ◽

Fractal Dimensions ◽

Rock Composition ◽

Slip Rates ◽

Shape Distribution ◽

Frictional Behavior ◽

Particle Size And Shape ◽

Frictional Melting ◽

Glass Compositions

In natural friction melts, or pseudotachylites, clast textures and glass compositions can influence the frictional behavior of faults hosting pseudotachylites, and are, in turn, sensitive to the processes involved in pseudotachylite formation. Quantification of these parameters in situations where the host rock composition and formation conditions are well-constrained, such as analogue experiments, may yield calibrations that can be employed in analysis of natural pseudotachylites. In this paper, we experimentally-generated pseudotachylites in granitoid rocks (tonalite and Westerly granite) at Pconf = 40 MPa and slip rates of ∼0.1 m s−1, comparable to the conditions under which natural pseudotachylite is known to form in Earth’s upper crust. We find variations in both clast textures and glass compositions that reflect formation processes, and probably influence the frictional behavior of similar natural faults hosting pseudotachylite. Quantification of particle size and shape distribution with a semi-automatic image analysis method, combined with analysis of glass and host-rock composition of these experimentally generated pseudotachylites, reveals that the textures of pseudotachylite material evolved by combinations of 1) comminution, 2) heterogeneous frictional flash melting, and 3) homogeneous (diffusive) clast melting and/or marginal decrepitation. Fractal dimensions of pseudotachylite-hosted clasts (D ∼ 3) that are greater than those of marginal fragmented host rock particles (gouge, D ∼ 2.4), reflect an increase of the intensity of comminution by slip localisation during a pre-melting phase. Chemical analyses demonstrate that these pseudotachylite glasses were generated by frictional flash melting, where host rock phases melt individually. Biotite is the least resistant to melting, feldspar intermediate, and quartz is the most resistant. The peudotachylite glass generated in these experiments has an alkaline composition, is depleted in SiO2 compared to the bulk host-rock, and shows heterogeneous compositions in a single sample related to proximity to host-rock minerals. The percentage contributions of host rock phases to the melt, calculated by a mixing model, shows that glass compositions are dominated by plagioclase and biotite. Within the melt, margins of clasts were dissolved uniformly by diffusion and/or affected by marginal decrepitation, resulting in convex and round shapes with convexities averaging ∼0.8 and circularities averaging ∼0.65.

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