(Ongoing) The influence of erosion and tectonics on the morphology and growth of stratovolcanoes: An application to the Philippines
BELSPO Postdoc Fellowship for non-EU Researchers, Postdoc Vrije Universiteit Brussel
The project has two components: the analogue of volcano erosion, which investigates how tectonics and precipitation erode volcanoes through time and the case study on the morphological classification and spatial distribution of Philippine volcanoes. The first component specifically studies the morphological evolution of volcanoes from an assumed youthful and conical initial shape into having deeply eroded terrains. Here, we design an experimental investigation that accommodates the contributions of both tectonic deformation (by movement of underlying fault) and erosion (by rainfall) on the overall evolution and development of volcano edifices. We link surface erosion and deformation features to tectonic and rainfall rates. This hopes to define the different erosional and morphological features associated with either or a combination of both erosion and tectonic deformation and how they evolve throughout the experiment. In the end, we hope to understand how the morphological changes are associated with varying stages of volcano growth, which will be useful for improving volcano hazard assessment in remote regions using remotely sensed imageries. The second component of the project is aimed in understanding how volcanoes in an island arc setting such as the Philippines are distributed and characterized based on their morphology. The Philippines is a composite terraine of both oceanic and continental crust materials and ophiolitic suites, located in a tectonically active region along a typhoon belt, and is an ideal place to study the factors that influence volcano edifice development. Specifically, we create a database of Philippine volcanoes based on morphological definition of a conical volcano; find a defining morphometric characteristics of each of the interpreted volcano classifications; describe the spatial distribution and alignments of volcanoes to understand how magma in this tectonic setting are propagated to the surface and what other factors control their propagation; and using their morphometry, morphologically classify volcanoes in the Philippines and suggest an evolutionary trend. These include describing the unique features in each class of volcanoes and relate this to the overall evolution of volcanic edifices in an island arc setting.
Developing a Sustainable pathway for the Philippine Nickel sector (SusNi)
April to September 2021 International Partnership Grant: £19,175 (DOST) and £62,037.60 (UK-NERC, BGS) Program Title: Sustainable Mineral Resources in the Philippines Co-implementing Agency: British Geological Survey Cooperating Agencies: Mines and Geosciences Bureau Region 13, Environmental Management Bureau Region 13, Nickel Mining Companies, Caraga Local Government Units, various people's organisations
The global demand for nickel is expected to increase rapidly by 2030, and suppliers are strategising “clean nickel” to attract more end-users and demonstrate that their environmental, social, and corporate governance challenges are addressed. The Philippines is the world’s second largest producer of nickel ore, after Indonesia (Research and Markets, 2019). The mining industry plays an important role in the economic development of the country and activities including the extraction and processing of ore and the construction of mining facilities can positively impact the environment and local people, if done sustainably. To enable sustainable mining practices, and produce “clean nickel,” we need to understand the nickel sector landscape, linkages, political issues, and the different roles, levels of influence, and requirements of various key actors through an interdisciplinary Strategic Environmental and Social Assessment (SESA).
This PPD grant aims to (1) create an initial interdisciplinary understanding of mining in the Philippines, the interactions between the key players and stakeholders, the perception of current mining practices in the local community, and the impacts on the environment, and (2) review the initial research questions raised about the direction of developing a sustainable pathway to “clean nickel” production through stakeholder consultations and a review of existing data, to (3) develop a large grant proposal highlighting a high level, interdisciplinary approach, SESA at its core. Caraga region having the largest nickel deposit in the Philippines, is an excellent case study for developing a roadmap for long-term, responsible, and inclusive development of the nickel sector in the country through SESA.
Lahar and pyroclastic flow inundation map for Mayon volcano, Philippines: essential after the 2014 renewed activity
Nila T. Gnamm Junior Faculty Grant 2014, Postdoc University at Buffalo
Mayon volcano, a composite cone of andesite and basaltic andesite lavas and associated pyroclastic flow and lahar deposits is very active. It has erupted about 50 times since its first recorded eruption in 1616. Volcanic phenomena such as lava flows, debris flows, pyroclastic flows and ash falls generated by the volcano during its eruption and even lahars during quiescent periods can affect everyone within its proximity as well as in distant areas. Eight large municipalities and cities surround the volcano and developed areas are situated on the lower slopes 8 to 14 km from the summit. It is for this reason that an updated 2009 map of lahar prone areas and pyroclastic flow simulations using Titan2D for modeling granular flows are presented here. The lahar prone areas are delineated by visual inspection of previous lahar deposits, gullies and other topographical features seen in Landsat L7 ETM+ SLC-off and L8 TIRS, and ALOS 2010 satellite data. The pyroclastic flow simulation input are based on the eruption reports and dome dimensions during its 2014 renewed activity, and elevation data from the 1996 AIRSAR DEM. The current lahar prone areas drawn are wider in the downstream areas compared to the earlier 2009 lahar hazard map with the addition of two lahar prone areas drawn on adjacent sides of the lava tongues on the southeast that includes the upper reaches of Mabinit and Padang gullies. The breach on the southeast sector of the crater is a major influence to the direction at which a PF is directed, towards Mabinit and Matanag gullies. In an event that the 2014 dome would collapse, it would cover an area of about 3106 m2 and maximum thickness of 6 m. For a column collapse generated by a Vulcanian eruption, most PF materials will take the same gullies but would cover about 1107 m2 and a maximum thickness of 14 m. Although the elevation data used in this report is not updated, which is crucial for studying both lahar and pyroclastic flow deposits, the results might give approximate lahar and pyroclastic flow prone areas and the methodology presented will be useful should an updated and free elevation data be available.
(Ongoing) The Canyonlands Slide: a large gravity slide, Canyonlands National Park region, Utah, USA
Postdoc University at Buffalo
The Grabens, Canyonlands National Park has repeating horsts and grabens morphology, similar to the Storegga slide (Norway). Here, extensional fracture system was enhanced by the dissolution and deformation of underlying salt towards the Colorado River. We recreate extension of a brittle layer over salt using scaled analog models of sand and silicone putty, and compare surface and internal structures with structural mapping of The Grabens and surrounding area.
We suggest that a 40-km long multistage, slow moving, gravity slide affects the Canyonlands region, from the head scarp grabens near Shay Mountain, down dip to the Colorado River. The Grabens is the toe of this slide consists of relatively homogeneous brittle layer overlying an inclined base of deforming ductile material of the Paradox Formation. The proposed Canyonlands slide covers ~800 km2, is ~1.7 km thick and has a volume of ~1,360 km3. The morphology suggests that repeating horsts and grabens are features of large-scale slides.
Based on the evolution of analogue slides, we suggest that Canyonlands slide started with the deformation and flow of the Paradox Formation at the end of the Pennsylvanian. Tilting to the west by the Monument upwarp in the Early Permian initiated extension to the northwest and later, to the west, due to northern confinement. Intrusion of the Shay Mountain laccolith during the Oligocene reactivated and enhanced this translation with Salt Creek, Shay, and Bridger Jack grabens accommodating the extension. During the last 500 ky, the Colorado River has been downcutting the slide toe causing a retrogressive failure that formed The Grabens.
Tectonic geomorphology and volcano-tectonic interaction in the eastern boundary of the Southern Cascades (Hat Creek Graben Region), California, USA
Postdoc University at Buffalo
The eastern boundary of the Southern Cascades (Hat Creek Graben region), California, USA, is an extensively faulted volcanic corridor between the Cascade Range and Modoc Plateau. The morphology of the region is a result of plate motions associated with different tectonic provinces, faulting, and recurring volcanic activity, making it an ideal place to study the interrelationship between tectonics, volcanoes, and geomorphology. We use the morphometry and spatial distribution of volcanoes and their interaction with regional structures to understand how long term regional deformation can affect volcano evolution. A database of volcanic centers and structures was created from interpretations of digital elevation models. Volcanic centers were classified by morphological type into cones,sub-cones, shields and massifs. A second classification by height separated the larger and smaller edifices, and revealed an evolutionary trend. Poisson Nearest Neighbor analysis showed that bigger volcanoes are spatially dispersed while smaller ones are clustered. Using volcano centroid locations, about 90 lineaments consisting of at least three centers within 6 km of one another were found, revealing that preferential north northwest-directed pathways control the transport of magma from the source to the surface, consistent with the strikes of the major fault systems. Most of the volcano crater and collapses car openings are perpendicular to the north northwest-directed maximum horizontal stress, expected for extensional environments with dominant normal faulting. Early in the history of a volcano or volcano cluster, melt propagates to the surface using the easiest and most efficient pathway, mostly controlled by the pre-existing normal faults and near-surface stress fields, as indicated by the pervasive vent alignments. Volcano growth continues to be dependent on the regional structures as indicated by the opening directions, suggesting structural control on the growth of the volcanic edifices. The results present a particularly well-defined case in which extension of a volcanic region is accommodated mostly by faulting, and only partly by intrusion to form volcanoes. This is attributed to a low magma supply rate.
The Structure, Morphology, and Surface Texture of Debris Avalanche Deposits: Field and Remote Sensing Mapping and Analogue Modelling
PhD Project
Flank collapse generates avalanches and large landslides that significantly change the shape of a volcano and alter the surrounding landscape. Most types of volcanoes experience flank collapse at some point during their development. In the Philippines, for example, the numerous volcanoes with breached edifices belong to the cone, subcone, and massif morphometric classes. Debris avalanches occur frequently on both volcanic and non-volcanic terrains making it an important geologic event to consider for hazard assessment.
Debris avalanche deposits (DAD) preserve surface and internal structures, morphology, and texture that can be used to determine transport type, deformation history, causal mechanism, and emplacement kinematics. However, natural DAD are often too vast and chaotic-seeming in the field so that structural and morphological mapping by remote sensing is a good complement to studying them. This study describes and analyses recurrent structural and morphological features of analogue models and natural DAD at Mt Iriga and Guinsaugon (Philippines), and uses several other examples at Mt Meager (Canada), and Storegga Slide (Norway). The study explores the use of analogue models as landslide kinematics, dynamics, and emplacement and causal mechanism indicators. Hummocks are identified as a key structural element of DAD.
Hummocks, a major DAD topographic feature, are formed as the mass in motion slides and evolves by progressive spreading and break up. Internally, high angle normal faults dissect hummocks and merge into low angle shear zones at the base of the slide zone. Hummock size distribution is related to lithology, initial position, and avalanche kinematics. Hummocks provide information on the transport conditions and initial composition of the landslide. Their geometry (size and shape), internal structures, and spatial distribution are kinematic indicators for landslides from development until emplacement and provide a framework for interpreting emplacement dynamics.
Experiments with curved analogue ramps show the development of an area of accumulation and thickening, where accelerating materials reach a gently sloped depositional surface. Experiments with straight ramps show a longer slides with continued extension by horst and graben structures and transtensional grabens. A thickened mass is found to subsequently remobilise and advance by secondary collapse. This set of experiments show that failure and transport surface morphology can influence the emplacement mechanism, morphology, and avalanche runout.
Structural and morphological mapping by remote sensing, and description of recurrent features at the remote and previously unmapped Süphan Dabı (Turkey), Cerro Pular-Pajonales (Argentina), and Tacna (Peru) DAD suggest scenarios, causes, triggering and emplacement mechanisms of these DAD. These are used to explain their avalanche kinematics and dynamics.Mapping DAD is a necessary step for identifying past events and existing hazards in specific areas. Identifying and describing the DAD structures and morphology will help understand the kinematics and dynamics of the emplaced avalanches.
Quantifying the factors that generated the November 2006 lahars of Mayon volcano, Philippines
MS Thesis
On 29-30 November 2006, heavy rains from Supertyphoon Durian remobilized volcanic debris on the southern and eastern slopes of Mount Mayon, generating major lahars that caused severe loss of life and property in downstream communities. The nearby Legaspi City weather station recorded 495.8 mm of rainfall over 1.5 days at rates as high as 47.5 mm/hour, far exceeding the initiation threshold for Mayon lahars. For about 18 hours, floods and lahars from the intense and prolonged rainfall overtopped river bends, breaching six dikes through which they created new paths, buried downstream communities in thick, widespread deposits, and caused most of the 1,266 fatalities. In order to mitigate damage from future lahars, the deposits were described and analyzed for clues to their generation and impact on structures and people. Post-disaster maps were generated from raw ASTER and SPOT images, using automated density slicing to characterize lahar deposits, flooded areas, croplands, and urbanized areas. Fieldwork was undertaken to check the accuracy of the maps, especially at the edges of the lahar deposits, and to measure the deposit thicknesses. The Durian event was exceptional in terms of rainfall intensity, but the dikes eventually failed because they were designed and built according to flood specifications, not to withstand major lahars. Lahar hazard maps were separately generated from time series analyses of multi-temporal images from 1992 to 2006 and FLO-2D lahar simulation using a 90 m SRTM and 10 m AIRSAR DEMs and PAGASA rainfall data.