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The Volume of the Tunguhraun and Dvergagígahraun Lavas, Central Iceland

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The Volume of the Tunguhraun and Dvergagígahraun Lavas, Central Iceland The Volume of the Tunguhraun and Dvergagígahraun Lavas, Central Iceland Julia Annina Heilig Faculty of Earth Sciences University of Iceland 2021 The Volume of the Tunguhraun and Dvergagígahraun Lavas, Central Iceland Julia Annina Heilig 10 ECTS thesis submitted in partial fulfillment of a Baccalaureus Scientiarum degree in Earth Sciences Advisor Ásta Rut Hjartardóttir Research specialist, PhD Faculty of Earth Sciences School of Engineering and Natural Sciences University of Iceland Reykjavík, May 2021 The Volume of the Tunguhraun and Dvergagígahraun Lavas, Central Iceland The Volume of the Tunguhraun and Dvergagígahraun Lavas 10 ECTS thesis submitted in partial fulfillment of a Baccalaureus Scientiarum degree in Earth Sciences Copyright © 2021 Julia Annina Heilig All rights reserved Faculty of Earth Sciences School of Engineering and Natural Sciences University of Iceland Sturlugata 7, 101 Reykjavík Telephone: 525 4000 Bibliographic information: Julia Annina Heilig, 2021, The Volume of the Tunguhraun and Dvergagígahraun Lavas, Bachelor‘s thesis, Faculty of Earth Sciences, University of Iceland, pp. 38. Abstract The Tunguhraun and Dvergagígahraun lavas are two lava fields in the central highland of Iceland. They are the only two eruptions of the Holocene that can be associated with the Tungnafellsjökull central volcano. Therefore, the understanding of Tungnafellsjökull‘s volcanic activity and behavior since the retreat of the glacier depends on research of those lava fields. Here, calculations of the volume and thickness of the Tunguhraun and Dvergagígahraun lavas are presented. Due to lack of data on the topography beneath these prehistoric lavas, an elevation model estimating the topography under the lavas was created, using elevation values around the lava fields and on the kipukas. For these elevation values, as well as those of the lava field, the ArcticDEM was used. Mapped outlines and the interpolated elevation models coupled with an elevation model of the current landscape provided the required data to calculate the approximate volumes of the two lava fields. The Tunguhraun lava is rather small and very thin with a volume of 0.15 km3 and an average thickness of 0.7 m. The Dvergagígahraun lava, on the other hand, is a bit thicker, but one of the smallest lava fields in Iceland, with a volume of 0.36 x 10-2 km3 and an average thickness of 3.1 m. The interpolation for the underlying topography is an estimation and might miss smaller depressions and elevations. As lava tends to flow into depressions, the calculated values might be underestimations. Since the topography in the area has a low relief, big differences are unlikely. Útdráttur Tunguhraun og Dvergagígahraun eru hraun á miðhálendi Íslands. Þau eru einu nútímahraunin sem tengd hafa verið megineldstöð Tungnafellsjökuls og eru rannsóknir á þeim því mikilvægar til að skilja virkni og hegðun eldstöðvakerfis Tungnafellsjökuls á nútíma. Í þessari rannsókn var rúmmál og þykkt Tunguhrauns og Dvergagígahrauns metið. Þar sem landslag undir hraununum er óþekkt var undirlag þeirra metið út frá landslagi í kringum þau og áætlað hæðarlíkan fyrir undirlag hraunsins búið til út frá þeim upplýsingum. Hæðargögnin til að áætla líkanið og hæðarupplýsingar fyrir hraunin sjálf voru frá ArcticDEM hæðarlíkaninu. Með því að nota kortlagningu af útlínum hraunanna, áætlaða hæðarlíkanið af undirlagi hraunanna og hæðarlíkan af núverandi yfirborði hraunanna var hægt að meta rúmmál þeirra. Tunguhraun er frekar lítið og hraunlag þess þunnt, það er 0,15 km3 að rúmmáli og meðalþykkt þess um 0,7 m. Dvergagígahraun er hins vegar þykkara að meðaltali en eitt af minnstu gosum á Íslandi, það er 0,36 x 10-2 km3 að rúmmáli og 3,1 m þykkt að meðaltali. Hraun rennur yfirleitt í lægðum og því getur verið að áætluðu hæðarlíkönin nái ekki að meta lægðirnar fyllilega. Niðurstöðurnar eru því líklega frekar vanmat en ofmat. Ólíklegt er að munurinn sé mikill þar sem landslagið á svæðinu er ekki mjög mishæðótt. Table of Contents List of Figures ................................................................................................................. vi Abbreviations .................................................................................................................. x Acknowledgements ......................................................................................................... xi 1 Introduction ................................................................................................................ 1 1.1 Volcanic Systems ................................................................................................ 1 1.2 Volcanism in Iceland ........................................................................................... 1 1.3 Tungnafellsjökull ................................................................................................. 5 1.4 Lava Volume Estimations .................................................................................... 9 2 Methods ..................................................................................................................... 11 3 Results ....................................................................................................................... 19 3.1 Profiles of the Tunguhraun Lava ........................................................................ 23 3.2 Profiles of the Dvergagígahraun Lava ................................................................ 24 4 Discussion .................................................................................................................. 27 4.1 Estimation of Accuracy ...................................................................................... 27 4.2 Volume Comparison .......................................................................................... 28 4.3 Flow Behavior of the Tunguhraun Lava ............................................................. 31 4.4 Fissure Orientation and Eruption of the Dvergagígahraun Lava.......................... 32 5 Conclusion ................................................................................................................. 33 References ...................................................................................................................... 35 v List of Figures Figure 1: The Atlantic Ocean with earthquake epicenters in red (1964-2006), which mark the mid-Atlantic plate boundary. Data are from the epicentral list of the NEIC, US Geological Survey. Figure from Einarsson (2008). ................... 3 Figure 2: Volcanic Systems of Iceland in yellow (from Einarsson and Sæmundsson, 1987) and earthquake epicenters from 1994–2007 in red (from the data bank of the Icelandic Meteorological Office). Different volcanic zones are indicated as: RPR Reykjanes Peninsula Rift, WVZ Western Volcanic Zone, SISZ South Iceland Seismic Zone, EVZ Eastern Volcanic Zone, CIVZ Central Iceland Volcanic Zone, NVZ Northern Volcanic Zone, GOR Grímsey Oblique Rift, HFZ Húsavík-Flatey Zone, ER Eyjafjarðaráll Rift, DZ Dalvík Zone, and SIVZ South Iceland Volcanic Zone. The abbreviations Kr, Ka, H, L, V stand for the central volcanoes of Krafla, Katla, Hengill, Langjökull, and Vestmannaeyjar. Figure taken from Einarsson (2008). ............................................................................................ 4 Figure 3: The spreading across the plate boundary in Iceland. Black arrows (ISNET measurements) and red arrows (CGPS stations in Iceland) indicate horizontal GPS station velocities relative to a fixed North American plate. Measurements span over a time interval of 1993-2004 for the ISNET measurements and 1999-2004 for the CGPS stations in Iceland. The green arrows show the predicted velocity of the Eurasian plate relative to a fixed North American plate from the NUVEL-1A plate motion model (DeMets et al., 1994) Figure taken from Árnadóttir et al., (2009). .................................. 5 Figure 4: InSAR images of the Gjálp eruption period. a) From 3rd of June 1995 to 6th of October 1996, b) from 31st of May 1995 to 3rd of October 1996, c) from 6th of October 1996 to 13th of July 1997, d) from 3rd of October 1996 to 23rd of September 1999. Arrows in figure c) indicate local deformation signals north of the Tungnafellsjökull glacier. The numbers in the lower right corners give the altitude of ambiguity in meters; it indicates the difference in topographic elevation that produces one fringe in an interferogram. The color index in figure a) applies to all four images. Figure taken from Pagli et al. (2007). .............................................................. 7 Figure 5: Seismic activity in the Tungnafellsjökull fissure swarm. a) Location map, fissure swarms from Einarsson and Sæmundsson (1987). b) The Bárðarbunga and Tungnafellsjökull volcanoes with earthquake epicenters (15th August 2014 to 10th April 2015) from the Icelandic Meterological Office (2016), seismic stations and GPS stations, eruption sites and modelled ring faults, sill, and dyke. c) Tungnafellsjökull with earthquakes from the 5th October 1996 to 11th April 1998 marked with light grey outlined dots, earthquakes from the 12th April 1998 to 14th August 2014 marked with transparent black outlined dots and earthquakes from the 15th August 2014 to 8th March 2015 marked with dark black outlined dots. The surface fractures are from Björnsdóttir and Einarsson (2013) and the TanDEM-X digital elevation model in the background of figures b) and c) vi was provided by the German Space Agency (DLR). Figure taken from
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