Gert Lube

Massey University · Institute of Agriculture and Environment

Pyroclastic surges are lethal hazards from volcanoes that exhibit enormous destructiveness through dynamic pressures of 10 ⁰ –10 ² kPa inside flows capable of obliterating reinforced buildings. However, to date, there are no measurements inside these currents to quantify the dynamics of this important hazard process. Here we show, through large-sca...

This repository contains data presented in the article “Destructiveness of pyroclastic surges controlled by turbulent fluctuations” by E. Brosch, G. Lube, M. Cerminara, T. Esposti-Ongaro, E.C.P. Breard, J. Dufek, B. Sovilla and L. Fullard. The article was published in Nature Communications (https://doi.org/10.1038/s41467-021-27517-9). A readme fil...

Numerical results of a two-layer depth-averaged model of pyroclastic density currents (PDCs) were compared with an experimental PDC generated at the international eruption simulator facility (the Pyroclastic flow Eruption Large-scale Experiment (PELE)) to establish a minimal dynamical model of PDCs with stratification of particle concentrations. In...

Numerical results of a two-layer depth-averaged model of pyroclastic density currents (PDCs) were compared with an experimental PDC generated at the international eruption simulator facility (the Pyroclastic flow Eruption Large-scale Experiment; PELE) to establish a minimal dynamical model of PDCs with stratification of particle concentrations. In...

The aim of this document is to define a Pyroclastic Density Currents (PDCs) benchmark based on a large-scale experiment to be used with numerical models at different levels of complexity. The document is organized as follows. Section 2 concisely describes the large-scale laboratory experiment setup and geometry, and the relevant specific bibliograp...

More than half of explosive volcanic eruptions contain multiple eruption phases with eruption dynamics (i.e., style, intensity, magnitude) varying with eruption progression. While probabilistic eruption forecast models constitute a useful tool for decision making during volcanic crises, the probabilistic forecast of likelihood, style and magnitude...

Mafic magmatism of the rifting Taupo Volcanic Zone (TVZ) of the North Island, New Zealand, is volumetrically minor, but is thought to tap the material that provides the heat source for voluminous rhyolite production through partial melting of the crust, which ultimately results in very large volume explosive eruptions. We have studied the major and...

Low to moderate-intensity eruptions (VEI ≤ 3) constitute the most frequent eruptions on historical time scales and can last from days to years. Direct observations of historical eruptions (e.g. Ruapehu 1995–1996, Nakadake 2003–2005, Etna 2002–2003) have highlighted the complexity of these eruptions, which often involve multiple phases and sudden ch...

Pyroclastic density currents (PDCs) are dangerous multiphase flows originating from volcanic eruptions. PDCs cause more than a third of volcanic fatalities globally and, therefore, development of robust PDC hazard models is a priority in volcanology and natural hazard science. However, the complexity of gas–particle interactions inside PDCs, as wel...

Dilute pyroclastic density currents (dilute PDCs) are frequent and highly dangerous flows of hot gas and particles occurring at explosive volcanoes. The study and interpretation of the sedimentary characteristics of their associated deposits is one of the most important approaches to better understand these violent phenomena and to characterise the...

Numerical models of pyroclastic currents are widely used for fundamental research and for hazard and risk modeling that supports decision-making and crisis management. Because of their potential high impact, the credibility and adequacy of models and simulations needs to be assessed by means of an established, consensual validation process. To defi...

Pyroclastic density currents are highly dangerous ground-hugging currents from volcanoes that cause >50% of volcanic fatalities globally. These hot mixtures of volcanic particles and gas exhibit remarkable fluidity, which allows them to transport thousands to millions of tonnes of volcanic material across the Earth’s surface over tens to hundreds o...

Geophysical fluid-granular flows, such as pyroclastic currents and debris flows, owe much of their runout and hazard behavior to the occurrence and time-variant decay of a flow-internal fluid pore pressure. However, modeling the effects of fluid pore pressure to forecast hazards is challenging because a unified method in Earth Sciences to quantitat...

The dynamics of granular flow in a rectangular silo with two symmetrically placed exit openings is investigated using particle image velocimetry (PIV), flow rate measurements and discrete element modelling (DEM). The flow of mustard seeds in a Perspex silo is recorded using a high-speed camera and the resulting image frames are analysed using PIV t...

Pyroclastic density currents (PDCs) are a significant volcanic hazard. However, their dominant transport mechanisms remain poorly understood, in part because of the large variability of PDC types and deposits. Here, we combine field data with experimental and numerical simulations to illuminate the twofold fate of particles settling from an ash clo...

Gravity-driven discharge experiments were performed in a perspex 3D flat bottomed silo which was filled with a granular material, and had a variable discharge orifice size. The granular material used was amaranth seed with an average diameter of 1 mm. Particle Image Velocimetry (PIV) analysis was performed on a high-speed video recording of the dis...

Mineral, groundmass and bulk rock chemical analyses of samples from the Tongariro Volcanic Complex were made to estimate depths of magma reservoirs for selected eruptive deposits. The sample set consists of two units from the 11,000 cal. yrs. B.P. Mangamate Formation (Te Rato and Wharepu) and more recent deposits from near 1717 cal. yrs. B.P. (Ngau...

Industrial storage of granular material using silos is common, however, improved understanding of silo flow is needed. Various continuum models attempt to describe the velocity of dense granular flow in silos. Kinematic, and recently, stochastic models, based upon the diffusion of some quantity, perform well when there is a single orifice, and when...

Terminus calving of icebergs is a common mass-loss mechanism from water-terminating glaciers globally, including the lake-calving glaciers in New Zealand’s central Southern Alps. Calving rates can increase dramatically in response to increases in ice velocity and/or retreat of the glacier margin. Here, we describe a large calving event (c. 4.5 × 10...

Granular material has the unique ability to transition between solid and liquid-like phases, but quantitative observations of the dynamics involved in this process remain rare. We hypothesize that granular packing of the solid phase has a leading control on this transition. To test this, we visualize the flow transitions that occur during discharge...

Pyroclastic density currents (PDCs) are the most lethal threat from volcanoes. While there are two main types of PDCs (fully turbulent, fully dilute pyroclastic surges and more concentrated pyroclastic flows encompassing non-turbulent to turbulent transport) pyroclastic flows, which are the subject of the present study, are far more complex than di...

Available online 20 August 2016 Editor: T.A. Mather Keywords: Te Maari hydrothermal eruption experimental fragmentation explosive energy ballistics Sudden hydrothermal eruptions occur in many volcanic settings and may include high-energy explosive phases. Ballistics launched by such events, together with ash plumes and pyroclastic density currents,...

Volcanic eruptions are at their most deadly when pyroclastic density currents sweep across landscapes to devastate everything in their path1, 2. The internal dynamics underpinning these hazards cannot be directly observed3. Here we present a quantitative view inside pyroclastic density currents by synthesizing their natural flow behaviour in large-...

The 2012 eruption of Tongariro volcano (New Zealand) produced highly mobile, low-temperature, blast-derived pyroclastic density currents after partial collapse of the western flank of the Upper Te Maari crater. Despite a low volume (340,000 m3), the flows traveled up to 2.5 km from source, covering a total area of 6.1 km2. Along one of the blast ax...

PELE is a large-scale facility for experimental studies of pyroclastic density currents (PDCs). It is used to generate high-energy currents involving 500–6,500 m3 natural volcanic material and air that achieve velocities of 7–30 ms−1, flow thicknesses of 2–4.5 m, and runouts of >35 m. The experimental PDCs are synthesized by a controlled ‘eruption...

In 2010, Gunung Merapi (Central Java, Indonesia) generated two violent eruption sequences on 26 October and 5 November culminating in widespread pyroclastic density currents (PDCs) associated with the destruction of lava domes. Tephra from PDC deposits were analysed to examine pre-dome collapse volatile behaviour and evidence of carbonate assimilat...

Analysis of the pre- and post-eruption topography, together with observations of the avalanche deposition sequence, yields a triggering mechanism for the 6 August 2012 eruption of Upper Te Maari. The avalanche was composed of a wedge of c. 683 000–774 000 m3 of coarse breccia, spatter and clay-rich tuffs and diamictons which slid from the western f...

On 6 August, 2012, Upper Te Maari Crater, Tongariro volcano, New Zealand, erupted for the first time in over one hundred years. Multiple vents were activated during the hydrothermal eruption, ejecting blocks up to 2.3 km and impacting ~ 2.6 km of the Tongariro Alpine Crossing (TAC) hiking track. Ballistic impact craters were mapped to calibrate a 3...

The weak geophysical precursors of the 6 August 2012 Te Maari eruption of Mt. Tongariro and a lack of obvious juvenile components in its proximal ballistic deposits imply that the eruption was caused by the sudden decompression of a sealed, hot hydrothermal system. Strong magmatic signals in pre- and post-eruption gas emissions indicate that fresh...

The 6 August 2012 Te Maari eruption produced violent and widespread “cold” Pyroclastic Density Currents (PDCs) following unroofing of the pressurized hydrothermal system. Despite an erupted volume of only ~ 5 x105 m3, and lacking any juvenile component, the 340,000 m3 of PDCs spread over an area of 6.1 km2 and had mobilities that were on the order...

The ballistic ejection of blocks during explosive eruptions constitutes a major hazard near active volcanoes. Fields of ballistic clasts can provide important clues towards quantifying the energy, dynamics and directionality of explosive events, but detailed datasets are rare. During the 6 August 2012 hydrothermal eruption of Upper Te Maari (Tongar...

Ballistics - bomb-sized pyroclasts that travel from volcanic source to final emplacement position along ballistic trajectories - represent a prime source of volcanic hazard, but their emplacement range, size, and density is useful to inverse model key eruption parameters related to their initial ejection velocity. Models and theory, however, have s...

Detailed analysis of volcanic craters and ballistic deposits can provide insight into eruption dynamics and evolution. As fully exposed craters and associated unmodified deposits are rarely preserved, the dynamics involved can only be inferred. Large-scale blast experiments conducted at the University at Buffalo Geohazards Field Station produced de...

In an ongoing effort to understand the relevant processes behind the formation of volcanic crater-, maar-, and diatreme structures, experiments producing craters with radii exceeding one meter were conducted at University at Buffalos Geohazards Field Station. A chemical explosive was used as energy source for the tests, and detonated in prepared te...

The 2010 eruption of Merapi was the second most deadly in the historic record of this volcano, claiming over 380 lives. By relating the observations of this eruption with detailed examination of deposit distribution, stratigraphy and sedimentology, a reconstruction of the properties of the pyroclastic density currents (PDCs) is presented, including...

Rain–triggered lahars represent a very common and dangerous phenomenon at Volcán de Colima, with between 15 and 20 events occurring per year including some that generate major damage to infrastructure. These flows initiate on the upper slope of the cone above 2500 m a.s.l. and usually erode and entrain material to transform into debris flows that d...

Glacier retreat resulting from iceberg calving represents one of the major controls on ice loss from water-terminating glaciers (ice sheets, tidewater and freshwater glaciers) globally. However, the impact that calving has on the transfer of mass between the cryosphere and hydrosphere is still heavily debated, and the physical mechanisms behind cal...

Lahars, debris flows, and sediment-rich floods are frequent and deadly hazards at all mountain-forming volcanoes. Their hazard potential is traditionally assessed through mass-conserving closed-system models, where peak conversion rates of potential energy to mechanical energy and hence maximum destruction potential are predicted to occur on the st...

Glacier retreat resulting from iceberg calving represents one of the major controls on ice loss from water-terminating glaciers (ice sheets, tidewater and freshwater glaciers) globally. However, the impact that calving has on the transfer of mass between the cryosphere and hydrosphere is still heavily debated, and the physical mechanisms behind cal...

Activity at Merapi Volcano, Indonesia, over the last few decades has been characterized by lava dome extrusion at variable rates and collapse of those domes, producing block-and-ash flows accompanied by pyroclastic surges. Two particularly large surge-producing dome collapse events occurred on 26 October and 5 November 2010, accompanied by explosio...

Lahars, debris flows and sediment-rich floods are frequent and deadly hazards at all mountain-forming volcanoes. Most current numerical models (including frequently- and worldwide-applied hazard assessment tools) are centered on the assumption that the main flow behavior is well captured by a closed system scheme. The closed system approach, which...

We present experimental results for the collapse of rectangular columns of sand down rough, inclined, parallel-walled channels. Results for basal inclination θ varying between 4.2° and 25° are compared with previous results for horizontal channels. Shallow-water theory can be usefully combined with scaling relationships obtained by dimensional anal...

We herein report an example of pyroclastic density current avulsion on 14 June 2006 at Merapi, Indonesia. Four discrete series of multiple dome collapses led to the generation of four individual block-and-ash flows into Kali Gendol valley. All four pyroclastic density currents locally overflowed the channel margins to devastate cultivated terraces...

Throughout the months of July and August 2010 a large section of the terminus of Tasman Glacier was observed to lift out of the water, eventually calving on the 22nd of August. Calving of this large section of the glacier likely occurred as a result of torque-induced buoyancy, caused by large areas of the glacier reaching flotation. Buoyancy of the...

Volcanic ice-slurry flows constitute a significant hazard at snow-capped volcanoes. These four-phase flows of ice, volcanic particles, water and air exhibit extreme rates of volumetric bulking and unusually high mobility. Thus far, the rapid melting and relocation of ice-slurry deposits have retarded detailed studies towards a better understanding...

Break-out floods from natural or artificial impoundments are significant hazards in many environments and regions around the world, resulting in loss of life, damage to infrastructure, and dramatic geomorphic changes due to the very high rate of energy expenditure associated with high flow velocities and depths in newly created or underfit pre-exis...

On 16 June 2006 an overpass of IKONOS coincided with the emplacement of an active block-and-ash flow fed by a lava dome collapse at Merapi Volcano (Java, Indonesia). It was the first moving pyroclastic flow recorded on a satellite image. The very high-spatial resolution of the image indicated the extent and impact of pyroclastic material that was d...

On 16 June 2006 an overpass of IKONOS coincided with the emplacement of an active block-and-ash flow fed by a lava dome collapse event at Merapi Volcano (Java, Indonesia). This was the first satellite image recorded for a moving pyroclastic flow. The very high-spatial resolution data displayed the extent and impact of the pyroclastic deposits empla...

At 11:18 h (New Zealand time, GMT+12) on 18 March 2007 an impoundment of 0.01 x 10(6) m(3) of tephra collapsed, releasing 1.3 x 10(6) 1113 of water from Crater Lake at 2536 m elevation on Mount Ruapehu. The lahar traveled 200 km along the Whangaehu River. Aerial LiDAR surveys of the upper 62 km of How path were made before and after the lahar. We p...

The near-invisibility of ice-slurry flows in the geological record belies their significant hazard at snow-capped volcanoes. These four-phase flows exhibit-extreme rates of volumetric bulking and unusually high mobility. Mechanisms of their motion are clarified through two examples generated on 25 September 2007 at Mount Ruapehu, New Zealand. Brief...

Conference title - Geological Society of New Zealand, New Zealand Geophysical Society, New Zealand Geochemical and Mineralogical Society joint conference, Copyright - GeoRef, Copyright 2012, American Geosciences Institute. Reference includes data supplied by Institute of Geological and Nuclear Sciences Limited (GNS Science), Lower Hutt, New Zealand...

A two layer model for the collapse and spreading of a granular column is presented. This model builds upon that of Larrieu et al. [J. Fluid Mech. 554, 669 (2006)] where the free fall collapse of the column and subsequent flow of material onto a plane is represented by a ``raining'' mass source term into a thin flowing layer of constant density. The...

Through laboratory experiments we investigate inertial granular flows created by the instantaneous release of particulate columns into wide, rectangular channels. These flows are characterized by their unsteady motion, large changes of the free surface with time, and the propagation towards the free surface of an internal interface separating stati...

Small-volume pyroclastic density currents (PDCs) are generated frequently during explosive eruptions with little warning. Assessing their hazard requires a physical understanding of their transport and sedimentation processes which is best achieved by the testing of experimental and numerical models of geophysical mass flows against natural flows a...

Conference title - IUGG XXIV general assembly, Copyright - GeoRef, Copyright 2012, American Geosciences Institute., Date revised - 2011-01-01, Language of summary - English, Pages - Abstract 6978, ProQuest ID - 840344052, SubjectsTermNotLitGenreText - Australasia; dams; debris flows; deposition; geologic hazards; lahars; mass movements; New Zealand...

Ruapehu lahars are typically derived from eruptions or outbursts from the hydrothermally heated Crater Lake. Hence the chemical contrast of this pulse of acidic brine into normal streamflow can be used, alongside sediment concentration and flow stage/discharge to understand the interaction of lahars and river water in their path. Observations of er...