Páll Einarsson

University of Iceland | HI · Institute of Earth Sciences

Eysteinn Tryggvason jarðeðlisfræðingur lést 11. janúar 2021, í hárri elli. Hann fæddist á Litlulaugum í Reykjadal 19. júlí 1924 og ólst þar upp í stórum systkinahópi. Foreldrar hans voru Tryggvi Sigtryggsson og Unnur Sigurjónsdóttir. Hann varð stúdent frá Menntaskólanum á Akureyri 1946 og fór til náms í veðurfræði og skyldum greinum við Oslóarháskó...

Með fráfalli Leós Kristjánssonar lýkur merkum kafla í sögu jarðvísindarannsókna á Íslandi. Hann hóf starfsferil sinn á upphafsárum mikilla byltinga í hugmyndaheimi jarðvísindanna. Kenningar um stórfelldar hreyfingar jarðskorpunnar voru að ryðja sér til rúms. Kenningin um færslu meginlandanna, landrekskenningin, gekk í endurnýjun lífdaga, og kenning...

The two volcanic eruptions of 2021 and 2022 at Fagradalsfjall in SW Iceland occurred within the Reykjanes Peninsula Oblique Rift, a segment of the complex boundary in Iceland between the North America and Eurasia Plates. Two of the plate boundary segments are highly oblique to the overall plate velocity vector, i.e., the Reykjanes Peninsula and the...

The formation of the island of Surtsey over 3.5 years, remains one of the best-documented volcanic, island-forming eruptions to date. The basaltic submarine volcanic activity was detected on November 14, 1963, where ocean depth was 130 m prior to the eruption at the southern end of the Vestmannaeyjar archipelago. The eruptions occurred in several p...

Increased rates of deformation and seismicity are well-established precursors to volcanic eruptions, and their interpretation forms the basis for eruption warnings worldwide. Rates of ground displacement and the number of earthquakes escalate before many eruptions1–3, as magma forces its way towards the surface. However, the pre-eruptive patterns o...

The basaltic effusive eruption at Mt. Fagradalsfjall lasted from 19 March to 18 September 2021, ending a 781‐year repose period on Reykjanes Peninsula, Iceland. By late September 2021, 33 near real‐time photogrammetric surveys were completed using satellite and airborne images, usually processed within 3–6 hr. The results provide unprecedented temp...

The Fagradalsfjall eruption started on the 19th of March 2021 on a ~180 m long eruptive fissure, following a dike intrusion which had been ongoing for approximately three weeks. The eruption focused shortly thereafter on two eruptive vents. In April, new fissure openings occurred northeast of the initial eruption on the 5th, 6/7th, 10th, and 13th o...

The emergence and growth of Surtsey during volcanic activity in 1963–1967, from an oceanic depth of 130 m off the south coast of Iceland, remains one of the best-documented island-forming eruptions to date. By extracting information from seismic bulletins and analyzing archived analog seismic data, principally from SID, the most sensitive station i...

A comprehensive catalogue of historical earthquakes, with accurate epicentres and harmonised magnitudes is a crucial resource for seismic hazard mapping. Here we update and combine catalogues from several sources to compile a catalogue of earthquakes in and near Iceland, in the years 1900–2019. In particular the epicentres are based on local inform...

The Hofsjökull volcanic system is located at the northern border of the Hreppar microplate on the Mid-Atlantic plate boundary in Iceland, between the more active Western and Eastern volcanic zones. In this study, fractures, and faults within the fissure swarms of the volcanic system were mapped and the throw and orientation of faults measured. This...

The history of seismography in Iceland began in 1909 with the installation of one horizontal Mainka seismograph in Reykjavík. Following a period of intermittent operation, regular operation was initiated in 1925 with the establishment of the Icelandic Meteorological Office. The number of stations increased gradually over the following decades, and...

A half century of monitoring of the Northern Volcanic Zone of Iceland, a branch of the North America—Eurasia plate boundary, shows that the seismicity is very unevenly distributed, both in time and space. The four central volcanoes at the boundary, Þeistareykir, Krafla, Fremrinámar, and Askja, show persistent but very low-level seismicity, spatiall...

In the Northern Volcanic Zone of Iceland, the geometry, kinematics and offset amount of the structures that form the active Krafla Rift were studied. This rift is composed of a central volcano and a swarm of extension fractures, normal faults and eruptive fissures, which were mapped and analysed through remote sensing and field techniques. In three...

The Tjörnes Fracture Zone (TFZ) connects the Kolbeinsey Ridge spreading axis north of Iceland and the Northern Volcanic Zone in Iceland. North-south trending ridges and basins are arranged along the 75 km wide west-northwest east-southeast trending TFZ. Major faults mark the southern boundary. Thick sediments and volcanics (the Tjörnes sequence) ha...

A comprehensive catalogue of historical earthquakes, with accurate epicentres and homogenised magnitudes is a crucial resource for seismic hazard mapping. Here we update and combine catalogues from several sources to compile a catalogue of earthquakes in and near Iceland, in the years 1900–2019. In particular the epicentres are based on local infor...

In the North Volcanic Zone of Iceland, we studied with the greatest possible detail the complete structural architecture and kinematics of the whole Theistareykir Fissure Swarm (ThFS), an N-S-trending, 70 km long active rift. We made about 7500 measurements along 6124 post-Late Glacial Maximum (LGM) extension fractures and faults, and 685 pre-LGM s...

On January 22, 2020, inflation of 3-4 mm per day started in the volcanic system of Svartsengi, within 5 km of several important infrastructure: a) the town of Grindavík (pop. 3300); b) the Svartsengi geothermal power plant, 75MWe, 150 MWth; c) and the Blue Lagoon geothermal spa, which has over 1 million annual visits. Grindavík is one of two towns...

Large volume effusive eruptions with relatively minor observed precursory signals are at odds with widely used models to interpret volcano deformation. Here we propose a new modelling framework that resolves this discrepancy by accounting for magma buoyancy, viscoelastic crustal properties, and sustained magma channels. At low magma accumulation ra...

Katla is one of the most active volcanoes in Iceland and is characterised by persistent seismicity. It is partly covered by the Mýrdalsjökull glacier and its historic activity is dominated by phreatomagmatic eruptions within the caldera associated with catastrophic glacial floods. In July 2011 a sudden jökulhlaup was released from the glacier, asso...

The magnitude distribution of caldera earthquakes in the subglacial Bárðarbunga volcano in Central Iceland, characterized by the b-value, shows a systematic variation that is consistent with stress changes anticipated in the roof of an inflating magma chamber beneath the caldera. The b-value was 0.83 prior to the rupture of the chamber in August 20...

Detecting unusual activity leading to the outbreak of a volcanic eruption is of vital importance for the short-term warning to the local population of an impending eruption. The varied volcano types of Iceland and range of ambient conditions at which eruptions occur offer an unusually wide spectrum of volcanic phenomena and volcanic hazards during...

A considerable part of the seismic risk to the capital area of Iceland is provided by a series of strike-slip faults at the mid-Atlantic plate boundary within a distance range of 15–35 km. About two thirds of the Icelandic population lives within this distance range from the source areas of M 6–6.5 earthquakes. The structure of the plate boundaries...

On August 16, 2014, an intense seismic swarm started below the eastern part of Bárðarbunga caldera in the north-western part of Vatnajökull ice cap, Iceland, marking the onset of a major rifting event. The intense seismicity, corroborated by a complicated deformation pattern, migrated away from the Bárðarbunga caldera for >45 km, until a small effu...

Major transform fault zones link extensional segments of the North American – Eurasian plate boundary as it transects the Iceland Hotspot. Changes in plate boundary geometry, involving ridge jumps, rift propagation, and related transform fault zone migration, have occurred as the boundary has moved relative to the hotspot. Reconfiguration of transf...

Hekla volcano is known to have erupted at least 23 times in historical time (last 1100 years); often producing mixed eruptions of tephra and lava. The lava flow volumes from the 20th century have amounted 80% to almost 100% of the entire erupted volume. Therefore, evaluating the extent and volume of individual lava flows is very important when asse...

Straddling the boundary between two of the major tectonic plates on Earth, Iceland offers unique conditions for engineering structures that require special attention. Urban areas are rapidly expanding into areas where the bedrock is cut by numerous active fractures and faults. The fissure swarm of the Krísuvík volcanic system runs through the outsk...

One of the World's premier field geologists, Kristján Sæmundsson led immense geological mapping programs and authored or co-authored nearly all geological maps of Iceland during the past half century, including the first modern bedrock and tectonic maps of the whole country. These monumental achievements collectively yield the most inclusive view o...

The Hengill Triple Junction in Iceland is formed by the intersection of the Western Volcanic Zone (WVZ), Reykjanes Peninsula Oblique Rift (RPOR) and a transform zone, the South Iceland Seismic Zone (SISZ). The 19 × 13 km² study area thus contains extensional structures related to volcanic systems of the two rift zones, Hengill and Hrómundartindur,...

Iceland, rising to more than 2 km above sea level, originates from the interaction of a mid-oceanic ridge and excessive mantle upwelling. The plate boundary between the North American and Eurasian plates traverses Iceland as a series of seismic and volcanic rift zones. The building blocks of the volcanic zones are about 32 volcanic systems, typical...

Networks of seismographs of high sensitivity have been in use in the vicinity of active volcanoes in Iceland since 1973. During this time, 21 confirmed eruptions have occurred and several intrusions where magma did not reach the surface. All these events have been accompanied by characteristic seismic activity. Long-term precursory activity is char...

The Reykjanes Peninsula Oblique Rift, a segment of the mid-Atlantic plate boundary, connects the Reykjanes Ridge to the rift zones of Iceland. The axis of the deformation zone of the plate boundary can be traced as a rather narrow epicentral zone of earthquakes that is highly oblique to the spreading direction of the North America Plate with respec...

GPS measurements spanning 2008 to 2014 are used to derive the surface velocity field across the Northern Volcanic Zone (NVZ) of Iceland, a subaerial part of the divergent boundary between the North-American and Eurasian plates. No volcanic activity nor magmatic intrusions were detected in the zone during this time-period. We infer an extensional ra...

Stress transfer associated with an earthquake, which may result in the seismic triggering of aftershocks (earthquake–earthquake interactions) and/or increased volcanic activity (earthquake–volcano interactions), is a well-documented phenomenon. However limited studies have been undertaken concerning volcanic triggering of activity at neighbouring v...

The Western Volcanic Zone (WVZ) in Iceland is ∼120 km long and 40 km wide. It offers an opportunity to study rift zones in a local ultra-slow spreading area close to a hotspot. Fractures were mapped from aerial photographs and digital elevation models. Most surface fractures are located in the southern part of the WVZ. The majority of the fractures...

A 23 hour tremor burst was recorded on July 8-9th 2011 at the Katla subglacial volcano, one of the most active and hazardous volcanoes in Iceland. This was associated with deepening of cauldrons on the ice cap and a glacial flood that caused damage to infrastructure. Increased earthquake activity within the caldera started a few days before and las...

Driven to collapse Volcanic eruptions occur frequently, but only rarely are they large enough to cause the top of the mountain to collapse and form a caldera. Gudmundsson et al. used a variety of geophysical tools to monitor the caldera formation that accompanied the 2014 Bárdarbunga volcanic eruption in Iceland. The volcanic edifice became unstabl...

The Surtsey Island was built from the seafloor at 130 m depth during the period 1963–1967. Two tephra cones formed above the sea level up to a height of 170 m. They were later partly covered by a lava shield when the magma conduit became isolated from the seawater and the activity changed into lava effusion. The final volume of Surtsey was 0.8 km3...

Relative location methods are commonly used to precisely locate earthquake clusters consisting of similar waveforms. Repeating waveforms are often recorded at volcanoes, where, however, the crust structure is expected to contain strong heterogeneities and therefore the 1D velocity model assumption that is made in most location strategies is not lik...

Our research is aimed at contributing to the general understanding of how transform-rift junctions work, a topic that can be studied in exceptional detail in North Iceland, where the active transform Husavik-Flatey Fault (HFF) connects with the Gudfinnugja Fault (GF), the westernmost structure of the Theistareykir Fissure Swarm (TFS). We studied in...

The Prestahnúkur fissure swarm is located within the ultraslowly spreading Western Volcanic Zone in Iceland. The fissure swarm is characterized by normal faults, open fractures, and evidence of subglacial fissure eruptions (tindars). In this study, fractures and faults within the Prestahnúkur fissure swarm were mapped in detail from aerial photogra...

A dike propagated ~ 48 km from the Bárðarbunga central volcano into one of its fissure swarms in August and early September 2014. The dike intrusion was accompanied by caldera subsidence in the ice-covered Bárðarbunga central volcano, as well as a propagating earthquake swarm, graben subsidence, and fissure eruptions in the fissure swarm. Most of t...

The Krafla rifting episode in 1975–1984, consisted of around 20 inflation-deflation events within the Krafla caldera, where magma accumulated during inflation periods and was intruded into the transecting fissure swarm during brief periods of deflation. We re-analyse geodetic and seismic data from the rifting episode and perform a time-dependent in...

Article written by the authors in 2009, never submitted.

Katla volcano is one of the most active and threatening volcanoes in Iceland. It is partly covered by Mýrdalsjökull glacier and the last explosive eruption to break the ice-surface occurred in 1918. The current repose time is the longest known in history. Increased seismicity and a tremor burst were recorded on July 8-9th 2011, associated with floo...

The Western Volcanic Zone in Iceland is an approximately 120 km long and 30-40 km wide branch of the Mid-Atlantic plate boundary, extending towards the north from its triple junction with the Reykjanes Oblique Rift and the South Iceland Seismic Zone. The Western Volcanic Zone is an ultra-slow spreading part of the plate boundary, since the spreadin...

A dike propagated laterally away from the Bárdarbunga central volcano in August 2014. The dike propagated about 48 km towards the northeast and north-northeast, mostly beneath the Vatnajökull glacier. However, the farthest 8 km of the dike were located north of the glacier, where the ice-free area allowed surface fractures and graben subsidence to...

The recent unrest and activity within the Bárðarbunga volcanic system, Iceland was initially identified by the onset of an intense earthquake swarm on the 16th August 2014 and concurrent movement registered at several nearby continuous GPS (cGPS) sites. Over the following weeks additional cGPS stations were installed, campaign sites were reoccupied...

The divergent plate boundaries of Iceland are marked by rift zones that consist of fissure swarms, i.e. areas with a high density of fractures, faults and eruptive fissures, generally considered to be the surface expressions of dikes. Monogenetic lava shields are common within the rift zones. They are gently sloping, circular cones created by erupt...

Few divergent plate boundaries are subaerial. Active rifts in Iceland provide valuable surface information on divergent spreading processes, rifting and faulting. The 200 km long and 50 km wide Northern Volcanic Rift Zone (NVZ) is composed of 7 volcanic systems, each consisting of a central volcano with a transecting fissure swarm. Fractures and po...

Crust at many divergent plate boundaries forms primarily by the injection of vertical sheet-like dykes, some tens of kilometres long1. Previous models of rifting events indicate either lateral dyke growth away from a feeding source, with propagation rates decreasing as the dyke lengthens2, 3, 4, or magma flowing vertically into dykes from an underl...

Located beneath Myrdalsjokull ice cap, Katla volcano is one of the most active and threatening volcanoes in Iceland, with at least 20 eruptions in the last 1100 years. The last phreatomagmatic eruption to break the ice-surface occurred in 1918 and signs of unrest have been detected since 1955, culminating in flooding from the ice cap in 1955, 1999...

Hekla is one of Iceland's most active volcanoes; its eruptions, characterized by surface fissuring and repeated lava flows during its post-glacial activity, have built up an 800 m high elongated mountain. Since 1970 it has erupted every ~ 10 years; the previous repose interval averaged ~ 60 years. For the last eruption in 2000 we constrain the magm...

The mid Atlantic ridge, separating the Eurasian and North American tectonic plates, is mostly buried below the Atlantic. There are, however, a few places where subaerial exposure of the mid-oceanic rift system allows geodetic observations of the deformation associated with the plate boundary. Iceland is the largest portion of the system emerged abo...