Agust Gudmundsson

Figure 1. (a) Las Canadas caldera and the stratovolcano Teide in Tenerife, Spain (Photo: NASA). How do collapse calderas form and why do some collapses result in very large eruptions? (b) Part of the Thingvellir Graben (and the stratovolcano Hengill) in Southwest Iceland. How can graben subsidence suppress or, alternatively, trigger eruptions? (c) Why did most of the feeder-dike of the 2021-2023 Fagradalsfjall eruptions in Iceland (seen here; Photo; T. Thordarson) become arrested, while a tiny 'finger' made it to the surface to erupt? And why are there so frequent eruptions in the nearby Sundhnukar Fissure, and still on-going? (d) Why do polygenetic volcanoes commonly stand 1-2 km above their surroundings (here: Augustine in Alaska, USA, during its 2005-2006 eruption; Photo: USGS/Cyrus Read).

Figure 1. (a) Las Canadas caldera and the stratovolcano Teide in Tenerife, Spain (Photo: NASA). How do collapse calderas form and why do some collapses result in very large eruptions? (b) Part of the Thingvellir Graben (and the stratovolcano Hengill) in Southwest Iceland. How can graben subsidence suppress or, alternatively, trigger eruptions? (c) Why did most of the feeder-dike of the 2021 Fagradalsfjall eruption in Iceland (seen here; Photo; T. Thordarson) become arrested, while a tiny 'finger' made it to the surface to erupt? (d) Why do polygenetic volcanoes commonly stand 1-2 km above their surroundings (here: Augustine in Alaska, USA, during its 2005-2006 eruption; Photo: USGS/Cyrus Read). Following the highly successful earlier runs of the Volcano course in the course will now run again, starting 16 October 2023. There will be 2 hours of webinars every week for 6 weeks in addition to the on-line lectures and exercises. In the webinars Agust Gudmundsson answers specific questions raised by participants, provides step-by-step solutions to numerous volcanological problems, and discusses further volcanological topics of special interests to the participants such as related to their own projects.

Interpretation A shift from polluting to clean fuels can reduce the average PM 2•5 personal exposure by 53% and thereby lower the death rate. For all fuel types, the estimated average HAP-PM 2•5 personal exposure and indoor concentrations exceed the WHO's Interim Target-1 average annual threshold. Policy interventions are urgently needed to greatly increase the use of clean fuels and stove technologies by 2030 to achieve the goal of affordable clean energy access, as set by the UN in 2015, and address health inequities in urban-rural settings.

Regional-scale urban residential densification provides an opportunity to tackle multiple challenges of sustainability in cities. But framework for detailed large-scale analysis of densification potentials and their integration with natural capital to assess the housing capacity is lacking. Using a combination of Machine Learning Random Forests algorithm and exploratory data analysis (EDA), we propose density scenarios and housing-capacity estimates for the potential residential lands in the Oxford-Cambridge Arc region (whose current population of 3.7 million is expected to increase up to 4.7 million in 2035) in the UK. A detailed analysis was done for Oxfordshire, assuming different densities in urban and rural areas and protecting lands with high-value natural capital from development. For a 30,000 dwellings-peryear scenario, the land allocated in Local Plans could cover housing growth in the four districts but not in Oxford City itself (which accounts for 48% of the demand); only 19% of the need would be covered in low but 59% in high housing density scenarios. Our study suggests a decision-support method for quantifying how the impact of housing growth on natural capital can be significantly reduced using more compact development patterns, protection of land with high-value natural capital, and use of low-biodiversity brownfield sites where available.

Fractures that form when fluid pressure ruptures the rock are referred to as fluid-driven fractures or hydrofractures. These include most dykes, inclined sheets and sills, but also many mineral veins and joints, as well as human-made hydraulic fractures. While considerable field and theoretical work has focused on the geometry and arrest of hydrofractures, how they select their propagation paths, particularly in layered and faulted rocks, has received less attention. Here I propose that of all the possible paths that a given hydrofracture may follow, it selects the path of least (minimum) action as determined by Hamilton's principle. This means that the selected path is that along which the energy transformed (released) multiplied by the time taken for the propagation is a minimum. Hydrofractures advance their tips/fronts in steps, with a time lag between the fracture front and the fluid front. In the present framework, each step is then controlled by Hamilton's principle. The results suggest that when the hosting rock body is regarded as homogeneous, isotropic and non-fractured, hydrofracture paths are everywhere perpendicular to the trajectories of the minimum compressive (maximum tensile) principal stress σ 3 and follow the trajectories of the maximum principal compressive stress σ 1. When applied to layered and faulted rock body, the results indicate that hydrofracture paths may follow existing faults for a while, depending primarily on (1) the dip of the fault (steep faults are the most likely to be used by vertically propagating hydrofractures), and (2) the tensile strength across the fault compared with the tensile strength of the host rock along a path following the direction of σ 1. The results suggest that hydrofractures may use faults as parts of their paths primarily if the fault is steeply dipping and with close to zero tensile strength.

Field observations of active and fossil natural geothermal fields indicate that geothermal fluids are primarily transported along dikes and fault zones. Fluid transport along dikes (commonly through fractures at their margins) is controlled by the cubic law where the volumetric flow rate depends on the aperture of the fracture in the 3rd power. Dikes (and inclined sheets) also act as heat sources for geothermal fields. In high-temperature fields in volcanoes in Iceland dikes and inclined sheets constitute 80-100% of the rock at crustal depths of 1.5-2 km. Holocene feeder-dikes are known to have increased the activity of associated geothermal fields. Fault zones transport geothermal fluids along their two main hydromechanical units, the core and the damage zone. The core is comparatively thin and primarily composed of breccia, gouge, and clay and related low-permeability porous materials. By contrast, the fault damage zone is characterised by fractures whose frequency is normally highest at the contact between the core and the damage zone. Fluid transport in the damage zone, and in the core following fault slip, is controlled by the cubic law. During non-slip periods fluid transport in the core is primarily controlled by Darcy's law. Secondary mineralisation (forming mineral veins and amygdales) tends to reduce the fault-zone permeability. Repeated earthquake activity is thus needed to maintain the permeability of fault zones in active natural geothermal fields.

Fractures that form when fluid pressure ruptures the rock are referred to as fluiddriven fractures or hydrofractures. These include most dikes, inclined sheets, and sills, but also many mineral veins and joints, as well as human-made hydraulic fractures. While considerable field and theoretical work has focused on the geometry and arrest of hydrofractures, how they select their propagation paths, particularly in layered and faulted rocks, has received less attention. Here I propose that of all the possible paths that a given hydrofracture may follow, it selects the path of least (minimum) action as determined by Hamilton's principle. This means that the selected path is the one along which the energy transformed (released) multiplied by the time taken for the propagation is a minimum. Hydrofractures advance their tips/fronts in steps, with a time lag between the fracture front and the fluid front. In the present framework, each step is then controlled by Hamilton's principle. The results suggest that when the hosting rock body is regarded as homogeneous, isotropic and non-fractured, hydrofracture paths are everywhere perpendicular to the trajectories of the minimum compressive (maximum tensile) principal stress σ3 and follow the trajectories of the maximum principal compressive stress σ1. When applied to layered and faulted rock body, the results indicate that hydrofracture paths may follow existing faults for a while, depending primarily on (1) the dip of the fault (steep faults are the most likely to be used by vertically propagating hydrofractures), and (2) the tensile strength across the fault as compared with the tensile strength of the host rock along a path following the direction of σ1. The results suggest that hydrofractures may use faults as parts of their paths primarily if the fault is steeply dipping and with close to zero tensile strength.

Figure 1. (a) Las Canadas caldera and the stratovolcano Teide in Tenerife, Spain (Photo: NASA). How do collapse calderas form and why do some collapses result in very large eruptions? (b) Part of the Thingvellir Graben (and the stratovolcano Hengill) in Southwest Iceland. How can graben subsidence suppress or, alternatively, trigger eruptions? (c) Why did most of the feeder-dike of the 2021 Fagradalsfjall eruption in Iceland (seen here; Photo; T. Thordarson) become arrested, while a tiny 'finger' made it to the surface to erupt? (d) Why do polygenetic volcanoes commonly stand 1-2 km above their surroundings (here: Augustine in Alaska, USA, during its 2005-2006 eruption; Photo: USGS/Cyrus Read).

The Tibesti Volcanic Province (TVP) in northwest Chad represents the second largest of the five Gharyan-Tibesti volcanic provinces and covers an area around 29,000 km 2. The other four provinces are in Libya, but all five provinces are from late Miocene to Quaternary and may have a common mantle source. The TVP, however, differs from the other four as regards volcano-tectonic processes, eruption style, and production of volcanic materials. The volcanic products of the TVP were erupted from the end of Miocene to late Pleistocene, range from basaltic to acidic, and suggest a double magma source-a shallow chamber fed by a deeper and larger reservoir. More specifically, field observations and numerical modelling results suggest that the basaltic magmas forming scoria cones, primarily at the periphery of magma in a deep-seated reservoir, triggered the formation of a ring-fault and the injection of a ring-dyke above the lateral margins of a shallow crustal magma chamber. Subsequently, the piston-like caldera subsidence helped to squeeze magma out of the shallow chamber resulting in large eruptions.

For more information, and to order, visit: www.cambridge.org/9781107024953 Volcanotectonics Understanding the Structure, Deformation and Dynamics of Volcanoes A volcanic eruption occurs when a magma-filled fracture propagates from its source to the surface. Analysing and understanding the conditions that allow this to happen constitute a major part of the scientific field of volcanotectonics. This new volume introduces this cutting-edge and interdisciplinary topic in volcanological research, which incorporates principles and methods from structural geology, tectonics, volcano-deformation studies, physical volcanology, seismology, and physics. It explains and illustrates the physical processes that operate inside volcanoes and which control the frequencies, locations, durations, and sizes of volcanic eruptions. Featuring a clear theoretical framework and helpful summary descriptions of various volcanic structures and products, as well as many worked examples and exercises, this book is an ideal resource for students, researchers and practitioners seeking an understanding the processes that give rise to volcanic deformation, earthquakes, and eruptions. on this title 28 February 2021 Expires

Volcanotectonics is comparatively new scientific field that combines various methods and techniques of geology and physics so as to understand the structure and behaviour of polygenetic (central) volcanoes and the conditions for their eruptions. More specifically, volcanotectonics uses the techniques and methods of tectonics, structural geology, geophysics, and physics to collect data on volcanoes, as well as to analyse and interpret the physical processes that generate those data. The focus is on processes responsible for periods of volcanic unrest, caldera collapses, and eruptions.

For basic science, one principal aim of volcanotectonics is to develop methods for reliable forecasting of eruptions. Accurate forecasting as regards the location, time, and magnitude of eruptions has long been a major goal in volcanology. Volcanotectonics provides a theoretical framework and understanding of the physical processes that take place inside volcanoes prior to eruptions, thereby offering methods and techniques that allow us to use data obtained during unrest periods to forecast eruptions. For applied science and human society, one principal aim of volcanotectonics is to develop methods for preventing very large eruptions. This second aim – namely methods that allow us to prevent very large eruptions - may come as a surprise to some, but is of fundamental importance for the future of human civilisation. Very large eruptions, whose eruptive volumes may be of the order of hundreds or thousands of cubic kilometres, provide existential threat to human civilisation.

The purpose of this book is to provide an overview of the scientific field of volcanotectonics. The book is primarily aimed at, first, undergraduate and graduate students in geology, geophysics, and geochemistry and, second, civil authorities, scientists, engineers, and other professionals who deal with volcanoes and the associated hazards in their work. The book has be designed so that it can be used (1) for an independent study, (2) as a textbook for a course on volcanotectonics, and (3) as a supplementary text for general courses on volcanology, structural geology, geology, geophysics, geothermics, and natural hazards.

Each chapter begins with an overview of the aims and ends with a summary of the main topics discussed. In addition there is a list of symbols used in the chapter. Important concepts and conclusions are in bold face. In volcanotectonics the focus is on quantitative results. This is reflected in the 68 worked examples (solved probems) most of which include calculations. In addition there are 253 exercises (supplementary problems), many of which also require calculations. The examples and exercises are meant to provide a deeper understanding of the basic principles of volcanotectonics and their use for understanding the formation of volcanoes, the physical processes that maintain their activities, and providing reliable eruption forecasts. While volcanic activity cannot be understood or forecasted without basic knowledge of the relevant physics, the physics presented in the book is mostly elementary and explained in detail. The only exception is part of Chapter 10, where more advanced physics is introduced to explain the propagation paths of magma-driven fractures.
I have taught much of the material in the book at various universities over the past 20 years to earth-science students in Norway, Germany, and England. In particular, many of the chapters form the basis of an undergraduate course on volcanology which I have taught in the past six years in England. Based on this experience, most of the material in the book should be suitable for earth-science students with a very modest knowledge of mathematics and physics.

Contents

Chapter 1. Introduction
Chapter 2. Volcanotectonic structures
Chapter 3. Volcanotectonic deformation
Chapter 4. Volcanic earthquakes
Chapter 5. Volcanotectonic processes
Chapter 6. Formation and dynamics of magma chambers and reservoirs
Chapter 7. Magma movement through the crust: dike paths
Chapter 8. Dynamics of volcanic eruptions
Chapter 9. Formation and evolution of volcanoes
Chapter 10. Understanding unrest and forecasting eruptions

Appendix A. Units, dimensions, and prefixes
Appendix B. The Greek alphabet
Appendix C. Some mathematical and physical constants
Appendix D. Elastic constants
Appendix E. Properties of some common crustal materials
Appendix F. Physical properties of lavas and magmas

The main magma source for eruptions on Etna (Italy) is poorly constrained. Here we use data on the size distributions of volcanic fissures/feeder-dykes, crater cones, dyke thicknesses, and lava flows to estimate the average magma volume flowing out of the chamber during eruptions and the volume of the chamber. For the past four centuries the average magma volume leaving the chamber during each eruption is estimated at 0.064 km 3. From the theory of poroelasticity the estimated chamber volume is then between 69 and 206 km 3. For comparison, a sill-like, circular chamber (an oblate ellipsoid) 1 km thick and 14 km in diameter would have a volume of about 154 km 3. the elastic strain energy stored in the host rock during inflation of such a chamber is about 2.8 × 10 14 J. estimating the surface energy of a typical dyke-fracture as about 10 7 J m −2 , the results suggest that the stored strain energy is sufficient to generate a dyke-fracture with an area of about 28 km 2. the average strike-dimension of volcanic fissures/feeder-dykes in Etna is about 2.7 km. It follows that the estimated strain energy is sufficient to generate a feeder-dyke with a strike-dimension of 2-3 km and with a dip-dimension as great as 10 km, agreeing with the maximum estimated depth of the magma chamber.

Volcanoes are open thermodynamic systems: they exchange energy and matter with their surroundings. In particular, volcanoes receive heat and magma from their source chambers. Volcanoes also store elastic (mainly strain) energy, both through work done on them by external (e.g. spreading-related) forces and, in particular, through magma-chamber expansion and inflation during unrest periods 1. The elastic energy is partly transformed into surface energy for the formation of fractures, such as tension fractures, normal faults, and dykes. In order to estimate the elastic energy available to form a feeder-dyke and squeeze magma out of the chamber and to the surface, information on the magma-chamber size is needed. Here we report for the first time the statistical size distributions of various types of volcanotectonic structures compiled from measurements on a single volcano, namely Etna (Italy), and show how these can be used to estimate its magma-chamber volume and elastic energy during inflation. The features measured include (i) lengths and orientations of volcanic (eruptive) fissures, (ii) thicknesses and orientations of dykes, (iii) diameters, volumes, and orientations of scoria cones, and (iv) combined volumes of feeder-dykes and lava flows. We show that the size distributions generally follow power laws. Using the combined volumes of feeder-dykes and lava flows together with basic poroelasticity theory, we estimate the likely volume of the main magma chamber of Etna. From the chamber volume we estimate the elastic strain energy stored in the volcano during inflation periods. From the estimated strain energy, we infer the potential of dykes injected from the magma chamber to reach the surface so as to supply magma to eruptions in Etna. Volcanotectonic setting and activity of etna. The activity of the Etna volcano, located along the eastern coast of Sicily (Italy), began at ~0.6 Ma 2 ; it is presently one of the world's most active volcanoes. Etna shows all the geochemical features of an 'anorogenic' volcano 3 although its location at the front of the Apennines

Buildings commonly have the largest share in the energy demand of a country, but they also offer sites for the generation of solar energy. Here we analyse the effects of street-canyon geometries on the solar access of street surfaces and facades of the adjacent buildings at a city scale, using the city of Geneva (Switzerland) as a case study. In particular, we measured the following geometric parameters of 1600 street canyons: orientation, width, length, sky-view factor (SVF), and aspect ratio. Street orientation has strong effect on received annual solar radiation by street surfaces and facades. For surfaces the highest received radiation (1000 kWhm-2) is for streets oriented WNE-ESE, whereas the highest radiation for facades (1400 kWhm-2) is for those facing SSW. The maximum monthly radiation received by street surfaces is 80 kWhm-2 whereas that received by facades is 100 kWhm-2. These maximum values are reached in June and July, but surfaces receive less radiation in all the months (the difference is mostly about 20 kWhm-2). Received solar radiation, both for street surfaces and facades, shows only moderate correlations with the other measured geometric parameters, namely street width, street length, aspect ratio, and SVF, the highest coefficient of determination (R2 = 0.55) being between received street-surface radiation and SVF. Also, street surfaces receive the highest radiation when the aspect ratio is low or the SVF high. For a street surface to receive comparatively high radiation in the months May to August, the street needs to be more than 15 m wide, have an aspect ratio of less than 2.0, and a SVF above 0.1. The results for facades in the same months are generally similar, except that they receive much more radiation than the street surfaces. A city-scale design that minimises solar access of streets surfaces during summers and maximises solar access of building facades during winters contributes to thermal comfort and may be partly reached through optimisation of urban compactness.

Correct interpretation of surface stresses and deformation or displacement during volcanotectonic episodes is of fundamental importance for hazard assessment and dyke-path forecasting. Here we present new general numerical models on the local stresses induced by arrested dykes. In the models, the crustal segments hosting the dyke vary greatly in mechanical properties, from uniform or non-layered (elastic half-spaces) to highly anisotropic (layers with strong contrast in Young's modulus). The shallow parts of active volcanoes and volcanic zones are normally highly anisotropic and some with open contacts. The numerical results show that, for a given surface deformation, non-layered (half-space) models underestimate the dyke overpressure/thickness needed and overestimate the likely depth to the tip of the dyke. Also, as the mechanical contrast between the layers increases, so does the stress dissipation and associated reduction in surface stresses (and associated fracturing). In the absence of open contacts, the distance between the two dyke-induced tensile and shear stress peaks (and fractures, if any) at the surface is roughly twice the depth to the tip of the dyke. The width of a graben, if it forms, should therefore be roughly twice the depth to the tip of the associated arrested dyke. When applied to the 2009 episode at Harrat Lunayyir, the main results are as follows. The entire 3-7 km wide fracture zone/graben formed during the episode is far too wide to have been generated by induced stresses of a single, arrested dyke. The eastern part of the zone/graben may have been generated by the inferred, arrested dyke, but the western zone primarily by regional extensional loading. The dyke tip was arrested at only a few hundred metres below the surface, the estimated thickness of the uppermost part of the dyke being between about 6 and 12 m. For the inferred dyke length (strike dimension) of about 14 km, this yields a dyke length/thickness ratio between 2400 and 1200, similar to commonly measured ratios of regional dykes in the field.

This is the first book describing the glorious geology of Iceland's Golden Circle and four additional excursions:(1) the beautiful valleys and mountains of the fjord of Hvalfjördur, (2) the unique landscape and geothermal fields of the Hengill Volcano, (3) the explosion craters, volcanic fissures, and lava fields of the Reykjanes Peninsula, and (4) the volcanoes (Hekla, Eyjafjallajökull, Katla), waterfalls, sandur plains, and rock columns of South Iceland. The Golden Circle offers a unique opportunity to observe and understand many of our planet's forces in action. These forces move the Earth's tectonic plates, rupture the crust, and generate earthquakes, volcanic eruptions, channels for rivers and waterfalls, and heat sources for hot springs and geysers. The Golden Circle includes the famous rifting and earthquake fracture sites at Thingvellir, the hot springs of the Geysir area, the waterfall of Gullfoss, and the Kerid volcanic crater. As the book is primarily intended for people with no background in geosciences, no geological knowledge is assumed and technical terms are avoided as far as possible (those used are explained in a glossary). With more than 240 illustrations – mostly photographs – explaining geological structures and processes, it is also a useful resource for geoscientists.

For human society, eruption sizes (eruptive volumes or masses) are of the greatest concern. In particular, the largest eruptions, producing volumes of the order of hundreds or thousands of cubic kilometres, provide, together with meteoritic impacts, the greatest natural threats to mankind. Eruptive volumes tend to follow power laws so that most eruptions are comparatively small whereas a few are very large. It follows that a while during most ruptures of the source chambers a small fraction of the magma leaves the chamber, in some ruptures a very large fraction of the magma leaves the chamber. Most explosive eruptions larger than about 25 km3 are associated with caldera collapse. In the standard 'under-pressure' ('lack of magmatic support') model, however, the collapse is the consequence, not the cause, of the large eruption. For poroelastic models, typically less than 4% of the magma in a felsic chamber and less than 0.1% of the magma in a mafic chamber leaves the chamber during rupture (and eventual eruption). In some caldera models, however, 20-70% of the magma is supposed to leave the chamber before the ring-fault forms and the caldera block begins to subside. In these models any amount of magma can flow out of the chamber following its rupture and there is apparently no way to forecast either the volume of magma injected from the chamber (hence the potential size of an eventual eruption) or the conditions for caldera collapse. An alternative model is proposed here. In this model normal (small) eruptions are controlled by standard poroelastity behaviour of the chamber, whereas large eruptions are controlled by chamber-volume reduction or shrinkage primarily through caldera/graben block subsidence into the chamber. Volcanotectonic stresses are then a major cause of ring-fault/graben boundary-fault formation. When large slips occur on these faults, the subsiding crustal block reduces the volume of the underlying chamber/reservoir, thereby maintaining its excess pressure so as to drive out magma for a much longer time during an eruption than is otherwise possible. As a consequence a much higher proportion of the magma in the chamber is driven or squeezed out during an eruption associated with caldera or graben subsidence than is possible during an ordinary poroelastic chamber behaviour. It follows that the volume of eruptive materials may approach the total volume of the chamber resulting in a large eruption. Here a large eruption is thus the consequence—not the cause—of the subsidence of the caldera/graben block. Thus, once the factors controlling large-scale subsidence of a caldera/graben block are established during a particular unrest/rifting episode, primarily using geodetic and seismic data, the probability of a large eruption can be assessed and used for reliable forecasting. Gudmundsson, A., 2015. Collapse-driven large eruptions.

The mechanical conditions for a volcanic eruption to occur are conceptually simple: a magma-driven fracture (normally a dyke) must be able to propagate from the source to the surface. The mechanics of small to moderate (eruptive volumes less than 10 km 3) is reasonably well understood, whereas that of large eruptions (eruptive volumes of 10-1000 km 3) is poorly understood. Here I propose that, while both large and small eruptions are primarily driven by elastic energy and may come from the same magma chambers and reservoirs, the mechanisms by which the elastic energy is transformed or relaxed in these eruptions are different. More specifically, during small to moderate eruptions, the excess pressure in the source (the primary pressure driving the eruption) falls exponentially until it approaches zero, whereby the feeder-dyke closes at its contact with the source and the eruption comes to an end. Under normal conditions, the ratio of the eruptive and intrusive material of the eruption to the volume of a totally molten shallow basaltic crustal magma chamber (at the common depth of 1-5 km) is about 1400, and that of a partially molten deep-seated basaltic magma reservoir (in the lower crust or upper mantle) is about 5000. Many magma chambers are partially molten, in which case the ratio could be close to that of reservoirs. Most magma chambers are estimated to be less than about 500 km 3 , for which the maximum eruptive volume would normally be about 0.4 km 3. An eruptive volume of 1 km 3 would require a totally molten chamber of about 1400 km 3. While chambers of this size certainly exist, witness the volumes of the largest eruptions, large eruptions of 10-1000 km 3 clearly require a different mechanism, namely one whereby the excess pressure maintenance during the eruption. I suggest that the primary excess-pressure maintenance mechanism is through caldera subsidence for shallow magma chambers and graben subsidence for deep-seated magma reservoirs. In this mechanism, it is the subsidence, of tectonic origin, and associated volume reduction (shrinkage) of the magma source that drives out an exceptionally large fraction of the magma in the source, thereby generating the large eruption. Most explosive eruptions that exceed volumes of about 25 km 3 , and many smaller, are associated with caldera collapses. The data presented suggest that many large effusive basaltic eruptions, in Iceland, in the United States, and elsewhere, are associated with large graben subsidences In terms of the present mechanism, successful forecasting large of eruptions requires understanding and monitoring of the volcanotectonic conditions that trigger large caldera and graben subsidences.

Abstract During their early evolution, strike-slip faults rapidly develop zones of rocks with widely different mechanical properties. These properties, in turn, largely determine the local stresses inside and around the fault zone and, thereby, the subsequent slips during fault rupture. It is common to distinguish between two main mechanical units: a fault core and a fault damage zone. The damage zone, which is normally much thicker than the core, contains some lenses of breccia, but is characterized by fractures of various types and ...

A volcanic eruption occurs when a magma-filled fracture propagates from its source to the surface. Analysing and understanding the conditions that allow this to happen constitute a major part of the scientific field of volcanotectonics. This new volume introduces this cutting-edge and interdisciplinary topic in volcanological research, which incorporates principles and methods from structural geology, tectonics, volcano-deformation studies, physical volcanology, seismology, and physics. It explains and illustrates the physical processes that operate inside volcanoes and which control the frequencies, locations, durations, and sizes of volcanic eruptions. Featuring a clear theoretical framework and helpful summary descriptions of various volcanic structures and products, as well as many worked examples and exercises, this book is an ideal resource for students, researchers and practitioners seeking an understanding of the processes that give rise to volcanic deformation, earthquakes, and eruptions.

Naturally-fractured carbonate reservoirs make up a large proportion (>60%) of the global hydrocarbon resources. During hydraulic fracturing, the mechanical behaviour of rocks and their heterogeneities, such as layering, faults and joints, impact permeability and are controlling factors which dictate the ease or difficulty of fluid flow in a system. This permeability reaches the percolation threshold when the fractures are linked and form a network. Such a network could, in turn, improve hydrocarbon recovery factor and make a project more economical.

We propose a methodology combining physical modelling and machine learning (ML) to estimate the apparent ground thermal diffusivity at the scale of a country. Based on ground temperature time series at different depths, we estimate the diffusivity at 49 Swiss stations using Fourier analysis. Using a geology database, the diffusivity estimations are cross-validated with typical values for common rocks. Random Forests, an ML algorithm, are used to train a model using the previous diffusivity estimations as output values and multiple geological, elevation and temperature features. The model, showing a testing error of 16.5%, is then used to perform the estimation of apparent diffusivity everywhere in Switzerland.

Regional-scale urban residential densification provides an opportunity to tackle multiple challenges of sustainability in cities. But framework for detailed large-scale analysis of densification potentials and their integration with natural capital to assess the housing capacity is lacking. Using a combination of Machine Learning Random Forests algorithm and exploratory data analysis (EDA), we propose density scenarios and housing-capacity estimates for the potential residential lands in the Oxford-Cambridge Arc region (whose current population of 3.7 million is expected to increase up to 4.7 million in 2035) in the UK. A detailed analysis was done for Oxfordshire, assuming different densities in urban and rural areas and protecting lands with high-value natural capital from development. For a 30,000 dwellings-peryear scenario, the land allocated in Local Plans could cover housing growth in the four districts but not in Oxford City itself (which accounts for 48% of the demand); only 19% of the need would be covered in low but 59% in high housing density scenarios. Our study suggests a decision-support method for quantifying how the impact of housing growth on natural capital can be significantly reduced using more compact development patterns, protection of land with high-value natural capital, and use of low-biodiversity brownfield sites where available.

In addition to socio-economic factors, major landforms may affect the city structure and urban form. Here we show that landforms have significant effects on the city shape and street patterns of the fast-growing Iranian cities of Dezful (a river) and Khorramabad (moun- tains and valleys), but no clear effects on the cities of Yazd and Nain. Also, where the street orientation is peaked, the Gibbs/Shannon entropy (a measure of dispersion or spread) is low, but increases as the distribution becomes more uniform because of landform constraints. The streets in the old inner parts of all the cities are, on average, shorter and denser (more streets per unit area) than the streets of the newer outer parts. The entropies of the outer parts are also greater than those of the inner parts, implying that the street-length distribution gradually becomes more dispersed or spread as the city expands. All these cities have been fast growing in the past decades, with the newer outer parts expanding rapidly. As shown here, the rapidly formed outer parts (with greater dispersion in street patterns) have significantly different textures from those of the older inner parts, indicating different functionality and growth processes. These quantitative methods for street-network analysis can be used worldwide, particularly for analysing the effects of landforms on city shape and texture.

ABSTRACT The morphology of street patterns has been the subject of many studies in recent decades. While some have noted the textural and morphological differences in various parts of many cities, there have been few attempts to quantify the street patterns that contribute to these differences. For this study, we measured and compared the trends (orientations) and lengths of 4,266 streets in the old, historical part of the city of Yazd, Iran, and 4,021 streets in the new part of the city to quantify their textural (morphological) differences and similarities. In the old part of the city, the street trends are orthogonal and follow a normal (one-peak) distribution. The street lengths range from 4-317 m, follow power-law distributions, and yield street-population entropies of 1.360-1.565. The power-law distributions indicate that, in the old part of Yazd, there are many short streets and few long ones. By contrast, in the new part of the city, the street trends follow a bimodal (two-peak) distribution. The street lengths vary from 5-596 m, follow power-law distributions, and yield entropies of 1.632-2.290. All of the street populations show strong linear correlations between their scaling exponents, length ranges, and entropies, a finding that agrees with results from other cities. With regard to city planning, these correlations indicate that, as a city grows and expands, its street networks often increase in length and entropy, requiring greater energy for construction. The innovative quantitative approach used to analyze city textures in this paper can also be used to compare the sizes and shapes of buildings within and among cities.

ABSTRACT Despite great progress in volcanology in the past decades, we still cannot make reliable forecasts as to the likely size (volume, mass) of an eruption once it has started. Empirical data collected from volcanoes worldwide indicates that the volumes (or masses) of eruptive materials in volcanic eruptions are heavy-tailed. This means that most of the volumes erupted from a given magma chamber are comparatively small. Yet, the same magma chamber can, under certain conditions, squeeze out large volumes of magma. To know these conditions is of fundamental importance for forecasting the likely size of an eruption. Thermodynamics provides the basis for understanding the elastic energy available to (i) propagate an injected dyke from the chamber and to the surface to feed an eruption, and (ii) squeeze magma out of the chamber during the eruption. The elastic energy consists of two main parts: first, the strain energy stored in the volcano before magma-chamber rupture and dyke injection, and, second, the work done through displacement of the flanks of the volcano (or the margins of a rift zone) and the expansion and shrinkage of the magma chamber itself. Other forms of energy in volcanoes - thermal, seismic, kinetic - are generally important but less so for squeezing magma out of a chamber during an eruption. Here we suggest that for (basaltic) eruptions in rift zones the strain energy is partly related to minor doming above the reservoir, and partly to stretching of the rift zone before rupture. The larger the reservoir, the larger is the stored strain energy before eruption. However, for the eruption to be really large, the strain energy has to accumulate in the entire crustal segment above the reservoir and there will be additional energy input into the system during the eruption which relates to the displacements of the boundary of the rift-zone segment. This is presumably why feeder dykes commonly propagate laterally at the surface following the initial fissure-segment formation. The additional energy through work goes into increasing the length and the opening of the volcanic fissure/feeder dyke, thereby allowing more magma to flow out of the chamber before it closes and the eruption ends. For stratovolcanoes, more strain energy can be stored before eruption if the volcano is composed of layers with widely different mechanical properties. Thus, other things being equal, a stratovolcano can normally store much more strain energy, for a given size of a magma chamber, than a basaltic edifice. It follows that when an eruption occurs in a stratovolcano, there is normally a higher proportion of its magma that is driven out than during an eruption in a basaltic volcano. For a gas-rich magma, the great compressibility of the gas may also help to maintain the excess pressure in the chamber so as to squeeze out more magma. Generally, the greater the stored strain energy before eruption, the greater is the likelihood that the eruption becomes large.

This dataset is a compiled chronostratigraphy for the volcanic island of Santorini, Greece. It comprises information on eruption dates, dating methods and numbers of eruptions of each type (Plinian, interplinian and lava), compiled from existing published sources (all references provided) and some supplementary fieldwork. The record is detailed and quantitative from the present day back to 224 ka, and less detailed and qualitative from 224 ka back to ~360 ka. Two maps are provided to give location context for the dataset, as well as a reference list, and other associated reading. This dataset forms part of the supplementary information for the publication 'Eruptive Activity of the Santorini Volcano Controlled by Sea Level Rise and Fall' by Satow et al. (2021) in Nature Geoscience- https://doi.org/10.1038/s41561-021-00783-4

Most volcanic eruptions occur when a magma-filled fracture propagates from its source to the surface. In rift zones outside central volcanoes the minimum principal compressive stress is normally horizontal so that most of the magma paths are vertical dikes. Many injected dikes, however, do not reach the surface to erupt but rather become arrested at various depths in the crust. Correct interpretation of dike-induced surface stresses and deformation during volcanotectonic episodes is of fundamental importance for hazard assessment and dike-path forecasting. Here we present new general numerical models on the local stresses induced by arrested vertical dikes in rift zones. In the models, the crustal segments hosting the dike vary greatly in mechanical properties, from uniform or non-layered (elastic half-spaces) to highly anisotropic (layers with strong contrast in Young’s modulus). The shallow parts of active volcanoes and volcanic rift zones are normally highly anisotropic. The nume...

Using Machine Learning (ML) algorithms for classification of the existing residential neighbourhoods and their spatial characteristics (e.g. density) so as to provide plausible scenarios for designing future sustainable housing is a novel application. Here we develop a methodology using a Random Forests algorithm (in combination with GIS spatial data processing) to detect and classify the residential neighbourhoods and their spatial characteristics within the region between Oxford and Cambridge, that is, the ‘Oxford-Cambridge Arc’. The classification model is based on four pre-defined urban classes, that is, Centre, Urban, Suburban, and Rural for the entire region. The resolution is a grid of 500 m × 500 m. The features for classification include (1) dwelling geometric attributes (e.g. garden size, building footprint area, building perimeter), (2) street networks (e.g. street length, street density, street connectivity), (3) dwelling density (number of housing units per hectare), (4) building residential types (detached, semi-detached, terraced, and flats), and (5) characteristics of the surrounding neighbourhoods. The classification results, with overall average accuracy of 80% (accuracy per class: Centre: 38%, Urban 91%, Suburban 83%, and Rural 77%), for the Arc region show that the most important variables were three characteristics of the surrounding area: residential footprint area, dwelling density, and number of private gardens. The results of the classification are used to establish a baseline for the current status of the residential neighbourhoods in the Arc region. The results bring data-driven decision-making processes to the level of local authority and policy makers in order to support sustainable housing development at the regional scale.

How green or environmentally friendly urban areas are in comparison with rural areas is a topic that has received much attention in recent years. This is understandable because urban areas already emit around 70% of the global greenhouse gases. This percentage is likely to rise in the near future. This follows because the majority of the future growth in the global population is expected to be in urban areas. Key questions for the future relate to how green the cities will be, especially in terms of energy use and the emission of global greenhouse gases. Are there, for example, particular sizes or forms of cities that are energy efficient and have comparatively low emission rates of greenhouse gases? One of the most important of the greenhouse gases is carbon dioxide (CO2), whose human-activity related emission is widely regarded as a major contributing factor to recent global warming. The rate of CO2 emission is thus one measure of how green or environmentally friendly urban areas are. In view of this, we here report the results of a study of estimated residential and transportation CO2 emissions (at local authority levels) from 406 areas in the UK in relation to various other factors such as population, population density, fuel consumption, and income. We present as maps the variation in CO2 per capita throughout the UK. For transport CO2, there are notable lows in emission per capita in large cities and urban areas such as London, Liverpool-Manchester, and Glasgow-Edinburgh. For residential CO2 per capita, the low values are again in the large cities and city clusters. The highest emission values, however, are very clearly in the rural areas, in particular in the western part of Wales, in North England and in Scotland, particularly in the Highlands. These variations can partly be explained in terms of the climate in these areas. The residential CO2 shows a close-to-linear scaling relation with population; that is, the scaling exponent is 0.92. This implies that as the population grows, residential CO2 emissions grow at a similar but slightly lower rate. By contrast, transport CO2 shows a clear sub-linear relation with population; that is, the scaling exponent is 0.66. This implies that as the population grows, transport CO2 emissions grow at a much lower rate. We also analysed the residential CO2 emission in relation to population density, measured as number of people per square kilometre (N/km2). The resulting relation is non-linear and suggests that as the density increases the CO2 emission per capita decreases somewhat. All these results may suggest that large-population and dense areas in the UK are greener in terms of CO2 emission than smaller ones. However, calculated population sizes depend on city-boundary definitions, and there is not at present a general agreement as to how city boundaries should be defined. Thus, populations may not necessarily be the best parameter to measure CO2 against, and the results need to be put into a wider context before firm conclusions can be drawn. For Greater London we analysed transport and residential CO2 emissions per capita in relation to urban density, fuel consumption, and income. The results show strong correlations between fuel consumption and CO2 emissions. Urban density also shows some correlation with residential CO2 emissions and fuel consumption, but hardly any with residential CO2 emissions per capita or average weekly income per household. By contrast, there is considerable correlation between income per household and residential CO2 emissions per capita. This last correlation illustrates how socio-economic factors may affect CO2 emissions and other environmental parameters that, to a large degree, determine whether or not an urban area is environmentally friendly or green.

The total population of the United Kingdom is expected to increase from 63 million in 2011 to 73 million people in 2037. This is an increase by 16% in 26 years, which puts the urban infrastructure, particularly the transportation infrastructure, under great pressure. Urban infrastructure, especially the transport infrastructure, to a large degree determines the overall shapes, productivity, and energy efficiency of cities. There has been considerable work on modelling the relations between urban growth patterns and transportation networks. By contrast, few studies have focused on the relations between the geometry of the transportation infrastructure and energy efficiency, in particular between innermost part (the core) and outer parts (the periphery) of cities. In many cities, the inner parts (constituting the core) of street networks are much older than, and commonly recognised as being geometrically different from, the newer and outer parts (constituting the periphery). To understand better the differences between the core and periphery parts of street networks, as well as their general structure and growth, in particular in relation to energy and efficiency, we analysed 41 street networks of small to large British cities with a total of more than 750 thousand streets. We also developed methods for quantifying the geometric (structural) differences between the core and periphery parts of the cities, and use the results to assess the efficiencies of the street-network in relation to city populations. The Gibbs/Shannon formula (a measure of spreading or dispersion) is used to calculate the street orientation-entropies and length-entropies of the resulting probability distributions. The street orientations vary from roughly orthogonal (grid-like) street sets with low entropy to close-to uniformly distributed street sets with high entropy. The length entropy shows a strong positive linear correlation with average street length and spacing and a negative correlation with street density. In comparison with the parts of the network periphery, the network cores have generally shorter streets, constituting low-entropy networks. This is in agreement with many of the cores being several hundred years old, or more, and thus constructed when much less energy was available than now. Therefore, many of the cores are the constructs of comparatively low-energy societies. There are two principal mechanisms by which a street network can accommodate increasing number of streets so as to be able to transport efficiently a growing population. One mechanism is through adding streets within the existing network. The other mechanism is through adding streets at the margins, that is, in the periphery parts, of the network. The first mechanism is referred to as expansion; the second is referred to as densification. We selected two British cities for a detailed analysis of the growth of their networks, namely Sheffield in England and Dundee in Scotland. Sheffield has a population of 555,500 (in 2010) and a total street number of 23,501. Tracing the evolution of the street network of Sheffield from 1736 to 2010, the results show that there was significant densification of the network in Sheffield, particularly during the period 1890-1950. Nevertheless, expansion has been the dominating mechanism of street-network growth during the entire period from 1736 to 2010. Dundee has a population 144,000 (in 2010) and a total street number of 9,616. Tracing the evolution of the street network of Dundee from 1600 to 2010, the results are significantly different from those for Sheffield. More specifically, whereas expansion dominated in the periods 1600–1776 and 1846–1912, expansion and densification are essentially similar in the other two periods considered, namely in 1776-1821 and 1912-2007. Results from cities in other countries show more extreme cases, where during certain periods densification entirely dominates. When as a city grows its network necessarily increases in total length but also spreads out (covers a larger area) and produces more entropy. This might indicate that when a city expands, its energy efficiency decreases. Clearly, the cost of the street network increases as the city expands. This follows because there is a certain constructional energy per kilometre for various types of roads and streets. Thus, for streets of a given type, to make them longer requires gradually more constructional energy. In order to assess the efficiencies of the street networks in the 41 cities, we compared the city populations with the street number and cumulative street length for each city. The number of streets ranges from 2226 (Winchester) to 240,611 (London), while the population ranges from 28,156 (Dover) to 7,825,200 (London). When plotting the population versus the number of streets, it is clear that cities with large populations need proportionally fewer streets and smaller cumulative total street length to transport that population…

Understanding the factors that affect dike propagation and dike arrest in the shallow crust, and subsequently control the associated dike-induced surface deformation is fundamental for volcanic hazard assessment. In this work, we focus on two dike segments associated with the Younger Stampar eruption (1210-1240 AD) on the Reykjanes Peninsula (SW Iceland). Both segments (spaced 30 m apart horizontally) were emplaced in the same heterogeneous crustal segment composed of lavas and tuffs. Here, the first dike to be emplaced fed a lava flow, while the second dike became arrested 5 m below the free surface without producing any brittle surface deformation. Therefore, this area represents an ideal case study to analyse the conditions that promote dike arrest or, alternatively, dike propagation to the surface. The outcrop also provides further examples of the absence of brittle deformation around a dike arrested just below the surface. For this work, we collected structural data from the di...

The seismogenic (brittle) part of an active major fault zone may contain of the order of 10 13 outcrop-scale (≥ 0.1 m strike or dip dimension) fractures and perhaps 10 23 grain-scale (≥ 1 mm) fractures. In active fault zones, the outcrop-scale fractures would be mainly in the damage zone whereas the grain-size slip planes would be primarily in the core. A fault zone receives energy mostly through plate-tectonic forces that drive the movement across the fault. For a fault zone of (temporary) constant volume, the available energy for work, and thus for producing earthquakes through fault slip, can be estimated from the Helmholtz free energy, F, given by F = U-TS. Here U is the internal energy of the fault zone, T the absolute temperature, and S entropy. TS represents the energy transformed, dissipated, as heat and unavailable. Alternatively we have F =-k B T ln Z, where k B is the Boltzmann constant (1.38 × 10 23 J K-1) and Z is the partition function. Differentiation of F with respect to temperature (at constant volume) then yields the Gibbs entropy formula probability of a fault falling in a particular bin in the distribution. This equation can be used to calculate the entropies of the size and orientation distributions of fractures in fault zones. We present results showing that fault dimensions and slips/displacements in some fault zones may follow partly exponential and partly power-law size distributions. Using the Gibbs-Shannon formula I show that the configuration entropy in a fault zone increases with time. It is proposed that as a fault zone evolves more and more of its energy is transformed into low-grade or unavailable energy through the term TS, implying that the fault-zone slip is gradually accommodated by creep or aseismic faulting. The results also suggest that if energy input into a fault zone increases, the tail of the fracture-size distribution becomes proportionally longer, that is, the fault zone generates more long fractures and large earthquakes, meaning that the length range increases. We show that the entropy increases with increasing fracture-length range. Since fault slip and earthquake magnitudes depend on earthquake-rupture size, it follows that if we can explain the rupture size distribution, we should be able to explain the earthquake-magnitude distribution.

I have just uploaded a video on YouTube about the structures of the beautiful central volcano Hengill, the main polygenetic volcano in the West Volcanic Zone of Iceland and the one that is closest to Reykjavik. The volcano is characterised by hyaloclastite ridges and large normal faults that generate a very special landscape. The most recent eruption was 2000 years ago, but two decades ago there was an unrest period with inflation and numerous earthquakes in the volcano. The Hengill Volcano and its surroundings also contain the largest geothermal power plants in Iceland.

Very large volcanic eruptions (of the order of 1000 km3) pose catastrophic risk, and some even existential risk, to humankind. Preventing potential very large eruptions from happening is therefore of vital importance for humankind. The main method proposed here is hydro-shearing of the host rock, particularly the roof, of the source magma chamber/reservoir so as to reduce the likelihood of magma-chamber rupture (with dike/inclined sheet injection) as well as reducing the strain energy available to drive an eruption – in case it happens. Hydro-shearing triggers numerous small fault slips (and earthquakes), thereby minimising the stress difference in the chamber roof – or any layer where the method is applied. Hydro-shearing thus brings the state of stress in the roof/layer closer to lithostatic, whereby all the principal stresses are the same and equal to the overburden pressure. For a lithostatic state of stress, there is no tendency to brittle deformation, either through faulting or dike/sheet injection. Thus, hydro-shearing transforms the roof/layer into a stress barrier, a seal, that should be able to prevent dike/sheet injections and, thereby, eruptions.

A volcanic eruption occurs when a magma-filled fracture, a dike or an inclined sheet, is able to propagate from its source (a magma chamber) to the surface. In this talk I explain how dikes/sheets choose among, theoretically, an infinite number of paths. I also explain how and why most dikes and sheets become arrested, that is, stop their propagation at depth in the crustal segment/volcano and never reach the surface to supply magma to an eruption. Being able to forecast the paths of dikes/sheets is of fundamental importance for hazard assessment during unrest periods and for understanding how volcanoes work.

Reply to Comment on ‘Eruptive activity of the Santorini Volcano controlled by sea-level rise and fall’

My colleagues and I published a paper in Nature Geoscience in August 2021 entitled: ‘Eruptive activity of the Santorini Volcano controlled by sea-level rise and fall’ (Nature Geoscience, 14, 586–592, 2021). In this paper we show that there is a strong correlation between sea-level changes and eruptions of Santorini. Furthermore, we provide a numerical model so as to explain this correlation. Soon after the paper’s publication Richard J Walker and colleagues sent us a numerical model and text implying that our numerical model was incorrect. (This I refer to as version 1 in the Reply below). Their boundary conditions, however, were entirely incorrect, as they came to realise themselves. Then they sent a new formal Comment to us and asked for response. (This I refer to as version 2 in the Reply below). Sometime later they submitted a somewhat modified version of the Comment to Nature Geoscience (this I refer to as version 3 in the Reply below), to which I responded formally in a Reply/Response, with input from my colleagues, and sent to Nature Geoscience in November 2021.

The title of the formal Comment by Richard J Walker et al. is ‘No demonstrated link between sea-level and eruption history at Santorini’. This is still the title on their uploaded versions on EarthArXiv where their Comment has been since 24 August 2021. Since I wrote my Reply in November 2021 (which they have seen), Walker et al. have made many changes to their original submitted Comment to us and to Nature Geoscience. Earlier they had taken out their statement (see Section 3 of the Reply) that ‘tensile failure would not be expected’ even if high tensile stress would concentrate in the roof of the magma chamber. I keep this paragraph in the Reply because I think that my clarification of this point has an educational value for volcanotectonic modelling in general.

In the latest version of the Comment by Walker et al. that I have seen, they have changed the Comment title to ´Santorini eruptions and sea level change´, thereby admitting that their earlier statement that there was no demonstrated link between the sea-level changes and the eruption history at Santorini was simply false (see Section 2 of the Reply). Also, in view of my comments in Section 1 of the Reply about their unjustified use of the viscosity for the mantle beneath Iceland in their model, they now refer to the viscosity as suitable for constant sea level. Since the paper (and the associated model) in Nature Geoscience is especially on the effect of ‘sea-level rise and fall’, that is, on changing sea level, their model has no relevance at all to the volcanotectonic processes our model is meant to explain.

The Comment has been on EarthArXiv since August 2021 but the versions that I have got have been changed many times. Unfortunately, I do not have time to write new versions of my Reply again and again in response to the changes in their Comment. I therefore decided to call it a day and publish my original Response here. I think the points I mention may have some educational value for those who want to make volcanotectonic models. Additionally, I provide an on-line course (https://ingeoexpert.com/en/courses-online/volcanoes-their-formation-form-and-function-course/) where fieldwork, analytical modelling, and numerical modelling are discussed in detail and applied to problems in volcanotectonics.

Figure 1. (a) Las Canadas caldera and the stratovolcano Teide in Tenerife, Spain (Photo: NASA). How do collapse calderas form and why do some collapses result in very large eruptions? (b) Part of the Thingvellir Graben (and the stratovolcano Hengill) in Southwest Iceland. How can graben subsidence suppress or, alternatively, trigger eruptions? (c) Why did most of the feeder-dike of the 2021 Fagradalsfjall eruption in Iceland (seen here; Photo; T. Thordarson) become arrested, while a tiny 'finger' made it to the surface to erupt? (d) Why do polygenetic volcanoes commonly stand 1-2 km above their surroundings (here: Augustine in Alaska, USA, during its 2005-2006 eruption; Photo: USGS/Cyrus Read).

An on-line course by Agust Gudmundsson starting 14 March 2022 Agust Gudmundsson answers specific questions raised by participants, provides step-by-step solutions to numerous volcanological problems, and discusses further volcanological topics of special interests to the participants such as related to their own projects.