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The erosional state of a landscape is often assessed through a series of metrics that quantify the morphology of drainage basins and divides. Such metrics have been well explored in tectonically active environments to evaluate the role of different processes in sculpting topography, yet relatively few works have applied these analyses to radial landforms such as volcanoes. We quantify drainage basin geometries on volcanic edifices of varying ages using common metrics (e.g., Hack's law, drainage density, and number of basins that reach the edifice summit, as well as basin hypsometry integral, length, width, relief, and average topographic slope). Relating these measurements to the log-mean age of activity for each edifice, we find that drainage density, basin hypsometry, basin length, and basin width quantify the degree of erosional maturity for these landforms. We also explore edifice drainage basin growth and competition by conducting a divide mobility analysis on the volcanoes, finding that young volcanoes are characterized by nearly uniform fluvial basins within unstable configurations that are more prone to divide migration. As basins on young volcanoes erode, they become less uniform but adapt to a more stable configuration with less divide migration. Finally, we analyze basin spatial geometries and outlet spacing on edifices, discovering an evolution in radial basin configurations that differ from typical linear mountain ranges. From these, we present a novel conceptual model for edifice degradation that allows new interpretations of composite volcano histories and provides predictive quantities for edifice morphologic evolution. [ABSTRACT FROM AUTHOR]

The erosional state of a landscape is often assessed through a series of metrics that quantify the morphology of drainage basins and divides. Such metrics have been well-explored in tectonically-active environments to evaluate the role of different processes in sculpting topography, yet relatively few works have applied these analyses to radial landforms such as volcanoes. We quantify drainage basin geometries on volcanic edifices of varying ages using common metrics (e.g., Hack's Law, drainage density, number of basins that reach the edifice summit, as well as basin hypsometry integral, length, width, relief, and average topographic slope). Relating these measurements to the log-mean age of activity for each edifice, we find that drainage density, basin hypsometry, basin length, and basin width quantify the degree of erosional maturity for these landforms. We also explore edifice drainage basin growth and competition by conducting a divide mobility analysis on the volcanoes, finding that young volcanoes are characterized by nearly-uniform basin geometries in unstable configurations that are prone to divide migration. Finally, we analyze basin spatial geometries and outlet spacing on edifices, discovering an evolution in radial basin configurations that differ from typical linear mountain ranges. From these, we present a novel conceptual model for edifice degradation that allows new interpretations of composite volcano histories and provides predictive quantities for edifice morphologic evolution. [ABSTRACT FROM AUTHOR]

The use of mass flow simulations in volcanic hazard zonation and mapping is often limited by model complexity (i.e. uncertainty in correct values of model parameters), a lack of model uncertainty quantification, and limited approaches to incorporate this uncertainty into hazard maps. When quantified, mass flow simulation errors are typically evaluated on a pixel-pair basis, using the difference between simulated and observed ("actual") map-cell values to evaluate the performance of a model. However, these comparisons conflate location and quantification errors, neglecting possible spatial autocorrelation of evaluated errors. As a result, model performance assessments typically yield moderate accuracy values. In this paper, similarly moderate accuracy values were found in a performance assessment of three depth-averaged numerical models using the 2012 debris avalanche from the Upper Te Maari crater, Tongariro Volcano, as a benchmark. To provide a fairer assessment of performance and evaluate spatial covariance of errors, we use a fuzzy set approach to indicate the proximity of similarly valued map cells. This "fuzzification" of simulated results yields improvements in targeted performance metrics relative to a length scale parameter at the expense of decreases in opposing metrics (e.g. fewer false negatives result in more false positives) and a reduction in resolution. The use of this approach to generate hazard zones incorporating the identified uncertainty and associated trade-offs is demonstrated and indicates a potential use for informed stakeholders by reducing the complexity of uncertainty estimation and supporting decision-making from simulated data. [ABSTRACT FROM AUTHOR]

The geotechnical and geomechanical characterization of volcanic material is critical for models of instability and mass flows, or interpreting geophysical signals of volcano unrest (e.g. volcano-seismic or geodetic). However, sampling a representative amount of material is challenging on active and hazardous volcanoes, which typically have difficult terrain. Additionally, testing the physical and mechanical properties of a large amount of material in the laboratory is unreasonable due to the excessive time requirements and high laboratory costs. Remote sensing, which produces large-scale and cost-effective images over relatively short time scales, can serve as a solution by complementing field and laboratory work, and thus improving our ability to monitor and forecast volcanic hazards. This project seeks to correlate geotechnical properties of key samples with electromagnetic (i.e. chemical) signatures collected from a hand-held spectral instrument, which are then used to statistically predict geotechnical properties of representative lithologies of Mt. Ruapehu volcano in New Zealand. Ultimately, we aim to transfer these predictions to a newly acquired aerial hyperspectral imagery of Mt Ruapehu.Hyperspectral imaging collects information from hundreds of spectral bands between 370 and 2500 nm, capable of identifying materials within each pixel of an image via the material's unique electromagnetic fingerprint. A hyperspectral aerial survey of Mt. Ruapehu, one of New Zealand's most active and visited volcanoes, was acquired using a fixed-wing aircraft in 2018. Over 30 locations with distinct hyperspectral signatures were visited to conduct in-situ strength and permeability measurements. The mineralogy, and specifically chemically altered minerals, were established using X-ray Fluorescence (XRF) and lab-based spectroscopy. The physically properties of the samples, including porosity, permeability, P- and S-wave velocities, and strength, were measured in the laboratory and correlated to the degree of alteration. We find that the degree of alteration (i.e. amount of clay minerals) is inversely correlated towards longer electromagnetic wavelengths, and is also positively correlated with porosity and inversely correlated with strength. This highlights the opportunity to fuse these datasets to predict geotechnical properties from hyperspectral imaging. [ABSTRACT FROM AUTHOR]

Mt Ruapehu is an andesitic to dacitic composite volcano active over the past 250 ky. Prolonged volcanic activity can induce surface and deep-seated hydrothermal alteration that turns primary pyroxene and plagioclase-bearing rocks into secondary clay minerals. Such clay-dominated alteration minerals have unique spectral response in the Near- to Shortwave Infrared (1000 to 2500 nm) of the electromagnetic spectrum. This study utilizes airborne hyperspectral imagery of Mt Ruapehu to map surface hydrothermal alteration zones. The hyperspectral image was acquired with an AisaFENIX full-spectrum (370-2500 nm) push-broom sensor in 2018. The hundreds of narrow spectral bands on this sensor allows detailed discrimination of surface mineralogy on a spatial scale of 1-2 m. The hydrothermal alteration was mapped using band ratios (e.g. bands centred around 2120 nm) and non-parametric supervised image classification approaches, such as support vector machine and random forest with recursive feature elimination. The resulting geological map is validated using existing geological maps and field validation during 2018. The lab-based spectroscopy identified kaolinite and smectite groups as the main mineral phase, using USGS spectral libraries and spectral angle mapper matching algorithm. This is interpreted to be due to shallow surface-related, low-temperature argillic alteration due to meteoric and hydrothermal fluids. The type and distribution of hydrothermal alteration can highlight potential source areas that are structurally weak and might provide material for mass flows (e.g. debris avalanches and landslides). The mapped surface alteration can change at depth, highlighting the limitation of airborne remote sensing approaches. Mt Ruapehu does not have any obvious shallow hydrothermal activity beyond the crater rim; however, older parts of the current volcanic edifice might be altered considerably, causing potential areas of weakness. This can be overcome in the future with the newly acquired aero-magnetic data that allows us to model the sub-surface distribution of hydrothermal alteration through the destruction of magnetite. The mapped source areas will provide inputs for future numerical simulations of mass flows hazards, contributing to long-term land-use planning, volcano monitoring, and natural hazard mitigation at Mt. Ruapehu. [ABSTRACT FROM AUTHOR]

Deception Island (DI) is one of the most active volcanoes in Antarctica, with more than 20 monogenetic eruptions during the Holocene. The latest episodes of 1967, 1969 and 1970 destroyed, or severely damaged, the scientific bases that operated on the island and have shown that volcanic activity on DI can become a concern for tourists, scientists and military personnel working on or near the island. Indeed, it is not possible to rule out the possibility of a future eruption in the future. One of the main problems at DI is related to the lack of data about the ages of most of the edifices, in order to evaluate the eruptive recurrence.The objective of this study is to carry out the morphometric analysis of the post-caldera volcanic structures (volcanic edifices and craters) recognizable on the island. This methodology has been used since the 70′s to analyse mafic monogenetic volcanoes but it has not been fully developed until recently. Several works were carried out in Campo de Calatrava-Ciudad Real, Tenerife, Gran Canaria and Lanzarote (Spain), Mauna Kea (USA) and Highlands of Bakony-Batalon (Hungary).This approach has been used at DI with the aim to establish a correlation between morphometry and the age of the post-caldera monogenetic landforms. The morphometric parameters include Crater maximum (Crmax) and minor (Crmin) diameter, Cone height (Hcomax and Hcomin), Crater depth (Cdep), Cone major (Comax) and minor (Comin) diameter, Cone slope (Scomax and Scomin) and Crater slope (Scrmax and Scrmin). One of the main peculiarity of DI is that these structures were probably affected by post-eruptive volcanic or erosive processes and that most of the volcanic edifices are tuff cone, as results of magma-water interaction. The results obtained will allow improving the estimation of the eruptive recurrence of the island and, in turn, fundamental point for the advising of the volcanic hazard.This research was supported by the MICINN grant CTM2011- 13578-E and was partially funded by the POSVOLDEC project (CTM2016-79617-P) (AEI/FEDER-UE). A.G. is grateful for her Ramón y Cajal contract (RYC-2012-11024). D.P. is grateful for his Beatriu de Pinós contract (2016 BP 00086). [ABSTRACT FROM AUTHOR]