Agust Gudmundsson

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• MSc, PhD Imperial College
• Chair of Structural Geology at Royal Holloway University of London

Fissure swarms and dike swarms in Iceland are 40-150 km long, 5-20 km wide, extend to depths of 10-20 km and contain 2 × 10 14 outcrop-scale ( 0.1 m) and 10 22-23 down to grain-scale ( 1 mm) fractures, suggesting that statistical physics is an appropriate method of analysis. Length-size distributions of 565 outcrop-scale Holocene fissures (tensio...

Shortly before the 2021 Fagradalsfjall eruption tomographic images indicated a large high V p /V s anomaly with a top at about 9 km depth directly below the ongoing seismic swarm. Using volcanotectonic principles we interpret this anomaly as part of the roof of a magma reservoir which, furthermore, ruptured on 24 February 2021. The roof rupture res...

Fractures that form when fluid pressure ruptures the rock are referred to as fluid-driven 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 hydrof...

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. Dik...

Shortly before the 2021 Fagradalsfjall eruption tomographic images indicated a large high Vp/Vs anomaly with a top at about 9 km depth directly below the ongoing seismic swarm. Using volcanotectonic principles we interpret this anomaly as part of the roof of a magma reservoir which, furthermore, ruptured on 24 February 2021. The roof rupture result...

Fissure swarms and dike swarms in Iceland are 40-150 km long, 5-20 km wide, extend to depths of 10-20 km and contain 2 × 10exp14 outcrop-scale ( 0.1 m) and 10 exp 22-23 down to grain-scale (1 mm) fractures, suggesting that statistical physics is an appropriate method of analysis. Length-size distributions of 565 outcrop-scale Holocene fissures (ten...

Fissure swarms and dike swarms in Iceland are 40-150 km long, 5-20 km wide, extend to depths of 10-20 km and contain 2 × 1014 outcrop-scale ( 0.1 m) and 1022-23 down to grain-scale ( 1 mm) fractures, suggesting that statistical physics is an appropriate method of analysis. Length-size distributions of 565 outcrop-scale Holocene fissures (tension fr...

I have just uploaded on my channel (Professor Agust Gudmundsson YouTube) a new video describing the geology, tectonics, and volcanic activity of the Reykjanes Peninsula. This video is for the general audience (as well as for professionals) and describes lava channels, the Sveifluhals hyaloclastite ridge, Lake Kleifarvatn and how its geometry is con...

All tectonic rock fractures develop in response to local stresses. The stress conditions for fracture formation has been analysed theoretically and experimentally and used to explain fracture patterns and activity in the field. How the local stresses themselves are generated, and then modified through fracture development, has received less attenti...

All tectonic rock fractures develop in response to local stresses. The stress conditions for fracture formation has been analysed theoretically and experimentally and used to explain fracture patterns and activity in the field. How the local stresses themselves are generated, and then modified through fracture development, has received less attenti...

I have just added two short talks on YouTube (Professor Agust Gudmundsson YouTube) on the indicated topics. These are meant to be the beginning talks of a series on Geological Activity Explained.

The Ayn Zayanah Al Coeffiah area is located in the eastern part of the city of Benghazi , northeast Libya. Ayn Zayanah Al Coeffiah is an urban area with an estimated population of 20,000. The exposed rocks in the area are mainly limestone and dolomitic limestone. The area is affected by abundant karstic features, involving caves and dolines with di...

I have just upoaded a talk on my YouTube channel (Professor Agust Gudmundsson Youtube) entitled: Ongoing volcanic eruptions, earthquakes, and associated hazards on the Reykjanes Peninsula, Iceland This talk focuses on the 5 eruptions that have occurred on the Sundhnukur volcanic fissure in the past 6 months and the associated hazards and earthquk...

Understanding the stress distribution around shallow magma chambers is vital for forecasting eruption sites and magma propagation directions. To achieve accurate forecasts, comprehensive insight into the stress field surrounding magma chambers and near the surface is essential. Existing stress models for pressurized magma chambers often assume a ho...

The focus is on understanding how and under what conditions volcanic eruptions occur and what methods can be used to understand better these conditions with a view of, eventually, being able to forecast volcanic eruptions.

The paper seeks to explain why multiple dikes - dikes formed when many magma injections follow the same path (with anywhere from days, weeks and years to decades, centuries, and millennia or more between successive injections) - are normally more likely to result in one or more magma injections reaching the surface to become a feeder-dike than sing...

Covid-19 has caused great challenges to the energy sector, particularly in residential buildings with low-income households. This study investigates the impact of the confinement measures due to the Covid-19 outbreak on the energy demand of seven residential archetype buildings in Greater London. Three levels of confinement for occupant schedules a...

According to WHO (World Health Organization), in 2020, 14% of people in global urban areas relied on polluting solid fuels and technologies, compared with 52% of the rural population. The health impacts of such inequality are massive. It was estimated that 3.2 million premature deaths per year (2020), particularly in low-income and middle-income co...

An online course on Volcanoes, how they form and function, begins 16 October

Understanding the stress distribution around shallow magma chambers is vital for predicting eruption sites and magma propagation directions. To achieve accurate predictions, comprehensive insight into the stress field surrounding magma chambers and near the surface is essential. Existing stress models for magma chamber inflation often assume a homo...

Background: Polluting fuels and inefficient stove technologies are still a leading cause of premature deaths worldwide, particularly in low-income and middle-income countries. Previous studies of global household air pollution (HAP) have neither considered the estimation of PM2·5 at national level nor the corresponding attributable mortality burde...

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 str...

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 alg...

Dear All, 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 re...

How volcanoes form and function, including new results from the recent eruptions in Iceland (Fagradalsfjall 2021 and 2022).

Here I describe the beautiful landscapes and exciting geology of the fjord Hvalfjördur, located just north of the capital Reykjavik. The deep erosion in this area allows us to study the internal structures of fossil central volcanoes, such as in the mountain Esja, and fossil rift zones. So we can compare what we see here, at about 1 km beneath th...

The physical processes that operate within, and beneath, a volcano control the frequency, duration, location, and size of volcanic eruptions. Volcanotectonics focuses on such processes, combining techniques, data, and ideas from structural geology, tectonics, volcano deformation, physical volcanology, seismology, petrology, rock and fracture mechan...

Volcanic and tectonic activities in the Aegean region have controlled the evolution of Santorini volcano, including changes in the shape and size of the island through time. Previous studies associate much of the island’s volcanic activity with the presence of regional faults, but a comprehensive volcanotectonic study that clarifies the relationshi...

Street networks are one of the very few types of complex networks where the history of the network can be traced over long periods of time. In this chapter, the authors introduce methods for quantifying the geometric characteristics of street networks and analyse the details of the evolution of the networks of Sheffield (UK), Khorramabad (Iran), an...

The volcanic eruption that began on 19 March 2021 at Fagradalsfjall is the first one to occur on the Reykjanes Peninsular for nearly 800 years and in Fagradalsfjall for about 6000 years. The feeder-dike was injected from a magma reservoir whose top is at about 10 km depth below the surface (but the reservoir itself reaches much greater depths). The...

Although many deep-seated magma reservoirs have been detected beneath active volcanic systems in Iceland in recent decades, none were detected beneath the 5 volcanic systems on the Reykjanes Peninsula (RP) before the year 2020. This area, close to Iceland’s capital Reykjavik, was subject to an unrest period with numerous earthquakes, beginning in D...

The increasing use of ground-source heat pumps (GSHPs) for heating and cooling of buildings raises questions regarding the technical potential of GSHPs and their impact on the temperature in the shallow subsurface. In this paper, we develop a method using Machine Learning to estimate the technical potential of shallow GSHPs, which enables such an e...

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 da...

A new course in volcanology, entitled: Volcanoes: Their Formation, Form, and Function

In 2020, Covid-19-related mobility restrictions resulted in the most extensive human-made air-quality changes ever recorded. The changes in mobility are quantified in terms of outdoor air pollution (concentrations of PM2.5 and NO2) and the associated health impacts in four UK cities (Greater London, Cardiff, Edinburgh and Belfast). After applying a...

For magma chambers to form or volcanic eruptions to occur magma must propagate through the crust as dikes, inclined sheets and sills. Most models that investigate magma paths assume the crust to be either homogeneous or horizontally layered, often composed of rocks of contrasting mechanical properties. In regions that have experienced orogenesis, l...

Sea-level change is thought to influence the frequencies of volcanic eruptions on glacial to interglacial timescales. However, the underlying physical processes and their importance relative to other influences (e.g. magma recharge rates), remain poorly understood. Here we compare a ~360 kyr long record of effusive and explosive eruptions from the...

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 km². 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...

Dykes and inclined sheets are known occasionally to exploit faults as parts of their paths, but the conditions that allow this to happen are still not fully understood. In this paper, we report field observations from a swarm composed of 91 segments of dykes and inclined sheets, the swarm being particularly well-exposed in the mechanically layered...

For magma chambers to form or volcanic eruptions to occur magma must propagate through the crust as dikes, inclined sheets and sills. The vast majority of models that investigate magma paths assume the crust to be either homogeneous or horizontally layered, often composed of rocks of contrasting mechanical properties. In subduction regions that hav...

Poster presented at EGU 2021

This is the first of several talks on the geology of Iceland. The talks are meant to be accessible for everyone. They should thus be useful for the general visitor to Iceland as well as for earth-science students. In particular, the talks should be of interest to people who not only wish to enjoy Iceland´s unique beauty, but also to appreciate and...

The extraction of shallow geothermal energy using borehole heat exchangers (BHEs) is a promising approach for decarbonisation of the heating sector. However, a dense deployment of BHEs may lead to thermal interference between neighbouring boreholes and thereby to over-exploitation of the heat capacity of the ground. Here we propose a novel method t...

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 propagati...

Fracture arrest in layered rock sequences is important in many geodynamic processes, such as dyke-fed volcanic eruptions, earthquake ruptures, landslides, and the evolution of plate boundaries. Yet it remains poorly understood. For example, we do not fully understand the conditions for dyke arrest (preventing potential eruptions) or hydraulic-fract...

This talk gives a general overview of how polygenetic volcanoes (stratovolcanoes, composite volcanoes, basaltic edifices) form and function, their relation to their source magma chamber, and the physical processes that control small and large volcanic eruptions.

Fracture arrest in layered rock sequences is important in many geodynamic processes, such as dyke-fed volcanic eruptions, earthquake ruptures, landslides, and the evolution of plate boundaries. Yet it remains poorly understood. For example, we do not fully understand the conditions for dyke arrest (preventing potential eruptions) or hydraulic-fract...

this conference paper was about numerical modeling of hydraulic fracturing in horizontal, vertical and inclined condition. This publication has been taken out of the event because of the event cancellation.

Currently, the sheet-intrusion paths and geometries, including the sheet opening/thickness as well as the depth to sheet tip, are commonly determined from geodetic surface data using elastic dislocation models. These models assume the volcanic zone/volcano to be an elastic half space of uniform mechanical properties. Field observations, however, sh...

Currently, the sheet-intrusion paths and geometries, including the sheet opening/thickness as well as the depth to sheet tip, are commonly determined from geodetic surface data using elastic dislocation models. These models assume the volcanic zone/volcano to be an elastic half space of uniform mechanical properties. Field observations, however, sh...

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...

It is of great importance in many fields to be able to forecast the likely propagation paths of fluid-driven factures. These include mineral veins, human-made hydraulic fractures, and dikes/inclined sheets. The physical principles that control the propagation of all fluid-driven fractures are the same. Here the focus is on dikes and inclined sheets...

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, ge...

The Early Holocene (12–8.2 cal ka) deglaciation and pulsed warming was associated in Iceland with two major generations of jökulhlaups around the Vatna ice-cap (Vatnajökull), at ca 11.4–11.2 cal ka and ca 10.4–9.9 cal ka, and major tephra emissions from the Grímsvötn and Bárðarbunga subglacial volcanoes. The earliest flood events were recorded inla...

During a volcanic unrest period with magma-chamber rupture, fluid-driven fractures (dykes) are injected either from deep reservoirs or shallow magma chambers. Subsequently, the dykes follow propagation paths towards the surface, some eventually reaching the surface to erupt while others become arrested. Here we study dyke paths resulting in eruptio...

Permafrost developed from Termination Ia (Bölling interstadial, 14.5 cal ka BP) in Northern Iceland, in answer to deglaciation. Permafrost persisted or even re-extended during the Preboreal cooling events (at 11.2, 10.3 and 9.3 cal ka BP) synchronic with pulsated glacial advances. It disappeared below 1000 masl during the Thermal Optimum (8-5 cal k...

Abstract The very shallow geothermal potential (vSGP) is increasingly recognized as a viable resource for providing clean thermal energy in urban and rural areas. This is primarily due to its reliability, low-cost installation, easy maintenance, and little constraints regarding ground-related laws and policies. We propose a methodology to extract t...

Here we present field observations of dike and fault interactions from two well-exposed calderas in Iceland and Greece. The Tertiary central volcano Hafnarfjall, in Southwest Iceland, exhibits a deeply eroded and uniquely well-exposed section of caldera ring-fault. The ring-fault represents the outermost fault complex of an elliptical caldera with...

Southern Iceland is one of the main outlets of the ice-sheet, and is subject to seismicity of both tectonic and volcanic origins, along the South Iceland Seismic Zone (SISZA sedimentary complex spanning Marine Isotopic Stage 6 to the present includes evidence of both activities. It includes a continuous sedimentary record since the Eemian interglac...

Conclude that for arrested dikes tension fractures and faults – in particular, the boundary faults of grabens – are most likely to form, if at all, in the location of the tensile/shear stress peaks and not, as is commonly suggested – from elastic half-space model - at the location of the surface uplift peaks. Elastic half-space models tend to overe...

The 2009 seismic episode at Harrat Lunayyir signalled a renewed geohazard and resulted in a regional dyke that propagated to a very shallow depth (a few hundred metres) below the surface. Since then, there has been an extensive research debate over the potential links between the volcanic/intrusive activity and tectonic processes, particularly beca...

During a volcanic unrest period with dike injection, one of the main tasks is to assess the geometry and the propagation path of the dike and, in particular, the likelihood of the dike reaching the surface to erupt. Currently, the dike path and geometry (including depth and opening/aperture) are both partly determined from geodetic surface data usi...

Mapping of lava flows based on remote sensing data of high accuracy has become a common tool for exploring volcanic eruptions in greater detail. Mapping data based on remote sensing data provides information on the location and flow direction of lava flows as well as their areas and enables the localisation of volcanic vents—valuable knowledge for...

During a volcanic unrest period with dike injection, one of the main tasks is to assess the geometry and the propagation path of the dike and, in particular, the likelihood of the dike reaching the surface to erupt. Currently, the dike path and geometry (including depth and opening/aperture) are both partly determined from geodetic surface data usi...