Plate boundary deformation and continuing deflation of the Askja volcano, North Iceland, determined with GPS, 1987–1993

Camitz, Johan; Sigmundsson, Freysteinn; Foulger, G. R.; Jahn, Cord-Hinrich; Völksen, Christof; Einarsson, Páll

doi:10.1007/bf00301404

Cited by 23 publications

(5 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Modeling of surface deformation during the entirety of the 1975 to 1984 rifting event does suggest a deeper magma source in addition to the 3 km deep chamber [ Tryggvason , 1986; Arnadottir et al , 1998], though given the available ground deformation data it is only possible to determine that its depth is >5 km. There has been no seismic imaging of Askja, but deflation modeling puts the chamber at 1.5–3.5 km depth [ Camitz et al , 1995; Tryggvason , 1989]. Finally, a magma chamber was imaged beneath Katla by Gudmundsson et al [1994], also at 3 km depth.…”

Section: Discussion Of Crustal Structurementioning

confidence: 99%

Plume‐driven plumbing and crustal formation in Iceland

et al. 2002

View full text Add to dashboard Cite

[1] Through combination of surface wave and body wave constraints we derive a threedimensional (3-D) crustal S velocity model and Moho map for Iceland. It reveals a vast plumbing system feeding mantle plume melt into upper crustal magma chambers where crustal formation takes place. The method is based on the partitioned waveform inversion to which we add additional observations. Love waves from six local events recorded on the HOTSPOT-SIL networks are fitted, S n travel times from the same events measured, previous observations of crustal thickness are added, and all three sets of constraints simultaneously inverted for our 3-D model. In the upper crust (0-15 km) an elongated low-velocity region extends along the length of the Northern, Eastern and Western Neovolcanic Zones. The lowest velocities (À7%) are found at 5-10 km below the two most active volcanic complexes: Hekla and Bárdarbunga-Grímsvötn. In the lower crust (>15 km) the low-velocity region can be represented as a vertical cylinder beneath central Iceland. The low-velocity structure is interpreted as the thermal halo of pipe work which connects the region of melt generation in the uppermost mantle beneath central Iceland to active volcanoes along the neovolcanic zones. Crustal thickness in Iceland varies from 15-20 km beneath the Reykjanes Peninsula, Krafla and the extinct Snaefellsnes rift zone, to 46 km beneath central Iceland. The average crustal thickness is 29 km. The variations in thickness can be explained in terms of the temporal variation in plume productivity over the last $20 Myr, the Snaefellsnes rift zone being active during a minimum in plume productivity. Variations in crustal thickness do not depart significantly from an isostatically predicted crustal thickness. The best fit linear isostatic relation implies an average density jump of 4% across the Moho. Rare earth element inversions of basalt compositions on Iceland suggest a melt thickness (i.e., crustal thickness) of 15-20 km, given passive upwelling. The observed crustal thickness of up to 46 km implies active fluxing of source material through the melt zone by the mantle plume at up to 3 times the passive rate.

show abstract

Section: Discussion Of Crustal Structurementioning

confidence: 99%

Plume‐driven plumbing and crustal formation in Iceland

et al. 2002

View full text Add to dashboard Cite

show abstract

“…We correct the GPS velocities for known sources of volcanic and geothermal deformation assuming the point sources listed in Table 2. The Askja caldera deflation has been extensively studied using leveling, GPS, and InSAR [Camitz et al, 1995;Sturkell and Sigmundsson, 2000;Pagli et al, 2006;Sturkell et al, 2006;de Zeeuw-van Dalfsen et al, 2012]. In each of these studies, a deflating point source of pressure [Mogi, 1958] centered in the caldera appears to explain a large part of the deformation signal.…”

Section: Volcanic and Geothermal Deformation Sourcesmentioning

confidence: 99%

Deformation in the Northern Volcanic Zone of Iceland 2008–2014: An interplay of tectonic, magmatic, and glacial isostatic deformation

et al. 2017

Self Cite

View full text Add to dashboard Cite

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 rate of 17.4 −0.3+0.2 mm/yr in direction 292.0 −0.6+0.5°, consistent with the results of previous studies and current plate motion models including MORVEL2010 and GEODVEL2010. The horizontal velocity field reveals about 50 km wide stretching zone caused by the divergent plate movements. Glacial isostatic adjustment (GIA) induces uplift of over 20 mm/yr at the northern edge of Vatnajökull ice cap and 3–4 mm/yr horizontal motion directed away from the ice cap. Deformation in the NVZ between 2008 and 2014 can be reproduced by a combination of models relating to several different processes: (i) Mogi sources for volcanic and geothermal deformation at the Askja and Krafla volcanoes, (ii) scaled version of a velocity field derived from a glacial isostatic model, and (iii) simple arctangent‐based model for secular plate spreading. We find the approximate location of the plate boundary spreading axis as well as its locking depth. The spreading axis lies through the Krafla, Fremrinámar, and Askja central volcanoes, the most active ones in the NVZ. It does not appear to follow the general direction of each fissure swarm but rather to change direction at the central volcanoes. The locking depth is on average within the 7–9 km range.

show abstract

“…Since 1983, various measurements indicate continuous deflation in Askja, but at a decreasing rate (Camitz et al 1995;de Zeeuw-Van Dalfsen et al 2005;Pagli et al 2006;Sturkell and Sigmundsson 2000;Sturkell et al 2006a;Sturkell et al 2006b;Tryggvason 1989).…”

Section: Regional Settingsmentioning

confidence: 99%

The fissure swarm of the Askja volcanic system along the divergent plate boundary of N Iceland

2009

View full text Add to dashboard Cite

Divergent plate boundaries, such as the one crossing Iceland, are characterized by a high density of subparallel volcanic fissures and tectonic fractures, collectively termed rift zones, or fissure swarms when extending from a specific volcano. Volcanic fissures and tectonic fractures in the fissure swarms are formed during rifting events, when magma intrudes fractures to form dikes and even feeds fissure eruptions. We mapped volcanic fissures and tectonic fractures in a part of the divergent plate boundary in northern Iceland. The study area is 1,800 km 2 , located within and north of the Askja central volcano. The style of fractures changes with distance from Askja. Close to Askja the swarm is dominated by eruptive fissures. The proportion of tectonic fractures gets larger with distance from Askja. This may indicate that magma pressure is generally higher in dikes close to Askja than farther away from it. Volcanic fissures and tectonic fractures are either oriented away from or concentric with the 3-4 identified calderas in Askja. The average azimuth of fissures and fractures in the area deviates significantly from the azimuth perpendicular to the direction of plate velocity. As this deviation decreases gradually northward, we suggest that the effect of the triple junction of the North American, Eurasian and the Hreppar microplate is a likely cause for this deviation. Shallow, tectonic earthquakes in the vicinity of Askja are often located in a relatively unfractured area between the fissure swarms of Askja and Kverkfjöll. These earthquakes are associated with strikeslip faulting according to fault plane solutions. We suggest that the latest magma intrusions into either the Askja or the Kverkfjöll fissure swarms rotated the maximum stress axis from being vertical to horizontal, causing the formation of strike-slip faults instead of the dilatational fractures related to the fissure swarms. The activity in different parts of the Askja fissure swarm is uneven in time and switches between subswarms, as shown by a fissure swarm that is exposed in an early Holocene lava NW of Herðubreið but disappears under a younger (3500-4500 BP) lava flow. We suggest that the location of inflation centres in Askja central volcano controls into which part of the Askja fissure swarm a dike propagates. The size and amount of fractures in the Kollóttadyngja lava shield decrease with increasing elevation. We suggest that this occurred as the depth to the propagating dike(s) was greater under central Kollóttadyngja than under its flanks, due to topography.

show abstract

Plate boundary deformation and continuing deflation of the Askja volcano, North Iceland, determined with GPS, 1987–1993

Cited by 23 publications

References 17 publications

Plume‐driven plumbing and crustal formation in Iceland

Plume‐driven plumbing and crustal formation in Iceland

Deformation in the Northern Volcanic Zone of Iceland 2008–2014: An interplay of tectonic, magmatic, and glacial isostatic deformation

The fissure swarm of the Askja volcanic system along the divergent plate boundary of N Iceland

Contact Info

Product

Resources

About