Abstract
The Nesjahraun is a basaltic lava flow erupted from a subaerial fissure, extending NE along the Þingvellir graben from the Hengill central volcano that produced pāhoehoe lava followed by ‘a‘ā. The Nesjahraun entered Iceland’s largest lake, Þingvallavatn, along its southern shore during both phases of the eruption and exemplifies lava flowing into water in a lacustrine environment in the absence of powerful wave action. This study combines airborne light detection and ranging, sidescan sonar and Chirp seismic data with field observations to investigate the behaviour of the lava as it entered the water. Pāhoehoe sheet lava was formed during the early stages of the eruption. Along the shoreline, stacks of thin (5–20 cm thick), vesicular, flows rest upon and surround low (<5 m) piles of coarse, unconsolidated, variably oxidised spatter. Clefts within the lava run inland from the lake. These are 2–5 m wide, >2 m deep, ∼50 m long, spaced ∼50 m apart and have sub-horizontal striations on the walls. They likely represent channels or collapsed tubes along which lava was delivered into the water. A circular rootless cone, Eldborg, formed when water infiltrated a lava tube. Offshore from the pāhoehoe lavas, the gradient of the flow surface steepens, suggesting a change in flow regime and the development of a talus ramp. Later, the flow was focused into a channel of ‘a‘ā lava, ∼200–350 m wide. This split into individual flow lobes 20–50 m wide along the shore. ‘A‘ā clinker is exposed on the water’s edge, as well as glassy sand and gravel, which has been locally intruded by small (<1 m), irregularly shaped, lava bodies. The cores of the flow lobes contain coherent, but hackly fractured lava. Mounds consisting predominantly of scoria lapilli and the large paired half-cone of Grámelur were formed in phreatomagmatic explosions. The ‘a‘ā flow can be identified underwater over 1 km offshore, and the sidescan data suggest that the flow lobes remained coherent flowing down a gradient of <10°. The Nesjahraun demonstrates that, even in the absence of ocean waves, phreatomagmatic explosions are ubiquitous and that pāhoehoe flows are much more likely to break up on entering the water than ‘a‘ā flows, which, with a higher flux and shallow underlying surface gradient, can penetrate water and remain coherent over distances of at least 1 km.
Similar content being viewed by others
References
Adalsteinsson H, Jónasson PM, Rist S (1992) Physical characteristics of Thingvallavatn, Iceland. Oikos 64(1/2):121–135. doi:10.2307/3545048
Bull JM, Minshull TA, Mitchell NC, Thors K, Dix JK, Best AI (2003) Fault and magmatic interaction within Iceland’s western rift over the last 9 kyr. Geophys J Int 154(1):F1–F8. doi:10.1046/j.1365-246X.2003.01990.x
Einarsson MA (1992) Climatic conditions of the Thingvallavatn area. Oikos 64(1/2):96–104. doi:10.2307/3545045
Fagents SA, Thordarson T (2007) Rootless volcanic cones in Iceland and on Mars. In: Chapman M (ed) The geology of Mars. Cambridge Planetary Science. Cambridge University Press, Cambridge, pp 151–177
Fisher R (1968) Puu Hou littoral cones, Hawaii. Geol Rundsch 57(3):837–864. doi:10.1007/BF01845368
GRASS Development Team (2009) Geographic Resources Analysis Support System (GRASS) software. Open source geospatial foundation project
Greeley R, Fagents S (2001) Icelandic pseudocraters as analogs to some volcanic cones on Mars. J Geophys Res E Planets 106(E9):20,527–20,546
Hamilton CW, Thordarson T, Fagents SA (2010) Explosive lava–water interactions I: architecture and emplacement chronology of volcanic rootless cone groups in the 1783–1784 Laki lava flow, Iceland. Bull Volcanol 72(4):449–467. doi:10.1007/s00445-009-0330-6
Hon K, Kauahikaua J, Denlinger R, Mackay K (1994) Emplacement and inflation of pahoehoe sheet flows: observations and measurements of active lava flows on Kilauea volcano, Hawaii. Geol Soc Amer Bull 106(3):351–370
Jones J (1970) Intraglacial volcanoes of the Laugarvatn region, southwest Iceland, II. J Geol 78:127–140
Jurado-Chichay Z, Rowland S, Walker G (1996) The formation of circular littoral cones from tube-fed pāhoehoe: Mauna Loa, Hawai’i. Bull Volcanol 57(7):471–482
Kauahikaua J, Sherrod D, Cashman K, Heliker C, Hon K, Mattox T, Johnson J (2003) Hawaiian lava-flow dynamics during the Pu‘u ‘O‘o-Kupaianaha eruption: a tale of two decades. In: Heliker C, Swanson D, Takahashi T (eds) The Pu‘u ‘O‘o-Kupaianaha eruption of Kilauea volcano, Hawai‘i: the first 20 years, no. 1676 in U.S. Geol Surv Prof Pap. U.S. Geological Survey, Reston, pp 63–88
Keszthelyi L, Thordarson T, McEwen A, Haack H, Guilbaud M, Self S, Rossi MJ (2004) Icelandic analogs to Martian flood lavas. Geochem Geophy Geosy 5:Q11,014. doi:10.1029/2004GC000758
Kilburn C (2000) Lava flows and flow fields. In: Sigurdsson H, Houghton B, McNutt SR, Rymer H, Stix J (eds) Encyclopedia of volcanoes. Academic, London, pp 291–306
Landmaelingar Islands (1988) Thingvallavatn 1613 II NA
Lescinsky D, Fink J (2000) Lava and ice interaction at stratovolcanoes: use of characteristic features to determine past glacial extents and future volcanic hazards. J Geophys Res B Solid Earth 105(B10):23,711–23,726
Masson DG, Harbitz CB, Wynn RB, Pedersen G, Lovholt F (2006) Submarine landslides: processes, triggers and hazard prediction. Philos Trans R Soc A Math Phys Eng Sci 364(1845):2009–2039. doi:10.1098/rsta.2006.1810
Mattox T, Mangan M (1997) Littoral hydrovolcanic explosions: a case study of lava-seawater interaction at Kilauea volcano. J Volcanol Geotherm Res 75(1–2):1–17
Mee K, Tuffen H, Gilbert JS (2005) Snow-contact volcanic facies at Nevados de Chillan volcano, Chile, and implications for reconstructing past eruptive environments. Bull Volcanol 68(4):363–376. doi:10.1007/s00445-005-0017-6
Mitchell NC, Beier C, Rosin PL, Quartau R, Tempera F (2008) Lava penetrating water: submarine lava flows around the coasts of Pico Island, Azores. Geochem Geophy Geosy 9(3):Q03,024. doi:10.1029/2007GC001725
Moore J, Ault W (1965) Historic littoral cones in Hawaii. Pac Sci 19(1):8–11
Moore J, Phillips RL, Grigg RW, Peterson DW, Swanson DA (1973) Flow of lava into the sea, 1969–1971, Kilauea volcano, Hawaii. Geol Soc Amer Bull 84(2):537–546
Passey SR, Bell BR (2007) Morphologies and emplacement mechanisms of the lava flows of the Faroe Islands Basalt group, Faroe Islands, NE Atlantic Ocean. Bull Volcanol 70(2):139–156. doi:10.1007/s00445-007-0125-6
Pebesma EJ, Wesseling CG (1998) Gstat: a program for geostatistical modelling, prediction and simulation. Comput Geosci 24(1):17–31. doi:10.1016/S0098-3004(97)00082-4
Rowland SK, Walker GP (1990) Pahoehoe and aa in Hawaii: volumetric flow rate controls the lava structure. Bull Volcanol 52(8):615–628. doi:10.1007/BF00301212
Saemundsson K (1992) Geology of the Thingvallavatn area. Oikos 64(1/2):40–68. doi:10.2307/3545042
Self S, Keszthelyi L, Thordarson T (1998) The importance of pahoehoe. Annu Rev Earth Planet Sci 26:81–110
Sinton J, Grönvold K, Sæmundsson K (2005) Postglacial eruptive history of the Western Volcanic Zone, Iceland. Geochem Geophy Geosy 6:Q12,009. doi:10.1029/2005GC001021
Skilling I (2002) Basaltic pahoehoe lava-fed deltas: large-scale characteristics, clast generation, emplacement processes and environmental discrimination. In: Smellie JL, Chapman M (eds) Volcano–ice interaction on earth and mars. Spec Publ Geol Soc Lond 202. Geological Society, London, pp 91–114
Skilling I, White J, McPhie J (2002) Peperite: a review of magma-sediment mingling. J Volcanol Geotherm Res 114(1–2):1–17
Smellie JL, Rocchi S, Armienti P (2010) Late Miocene volcanic sequences in northern Victoria Land, Antarctica: products of glaciovolcanic eruptions under different thermal regimes. Bull Volcanol 73(1):1–25. doi:10.1007/s00445-010-0399-y
Stevenson JA, Sun X, Mitchell NC (2010) Despeckling SRTM and other topographic data with a denoising algorithm. Geomorphology 114(3):238–252. doi:10.1016/j.geomorph.2009.07.006
Stevenson JA, Mitchell NC, Cassidy M, Pinkerton H (2011) Widespread inflation and drainage of a pāhoehoe flow field: the Nesjahraun, Þingvellir, Iceland. Bull Volcanol. doi:10.1007/s00445-011-04282-z
Sun X, Rosin P, Martin R, Langbein F (2007) Fast and effective feature-preserving mesh denoising. IEEE Trans Vis Comput Graph 13(5):925–938
Swanson D (1973) Pahoehoe flows from the 1969-1971 Mauna Ulu eruption, Kilauea Volcano, Hawaii. Geol Soc Amer Bull 84(2):615–626
Thors K (1992) Bedrock, sediments, and faults in Thingvallavatn. Oikos 64(1/2):69–79. doi:10.2307/3545043
Tribble G (1991) Underwater observations of active lava flows from Kilauea volcano, Hawaii. Geology 19(6):633–636
Tucker D, Scott K (2009) Structures and facies associated with the flow of subaerial basaltic lava into a deep freshwater lake: the Sulphur Creek lava flow, North Cascades, Washington. J Volcanol Geotherm Res 185(4):311–322
Umino S, Lipman P, Obata S (2000) Subaqueous lava flow lobes, observed on ROV dives off Hawaii. Geology 28(6):503–506
Umino S, Nonaka M, Kauahikaua J (2006) Emplacement of subaerial pahoehoe lava sheet flows into water: 1990 Kūpaianaha flow of Kilauea volcano at Kaimū Bay, Hawai’i. Bull Volcanol 69(2):125–139
Wohletz K (2002) Water/magma interaction: some theory and experiments on peperite formation. J Volcanol Geotherm Res 114(1–2):19–35. doi:10.1016/S0377-0273(01)00280-3
Acknowledgements
LiDAR data were collected on NERC Airborne Research and Survey Facility flight IPY07-02. Raw data are available for download from http://www.neodc.rl.ac.uk/. Chirp and sidescan data were collected with J Bull, T Minshull and A Best and funded by the Royal Society. JAS is supported by EPSRC grant EP/C007972/1 (PI: Paul Rosin, Cardiff University). Fieldwork by JAS was supported by an Elspeth Matthews grant from the Geological Society. Gretar Ívarsson (Orkuveita Reykjavíkur) and Gemma Gwynne provided assistance in the field. J Kauahikaua and C Hamilton are thanked for constructive reviews.
Author information
Authors and Affiliations
Corresponding author
Additional information
Editorial responsibility: J.D.L. White
Rights and permissions
About this article
Cite this article
Stevenson, J.A., Mitchell, N.C., Mochrie, F. et al. Lava penetrating water: the different behaviours of pāhoehoe and ‘a‘ā at the Nesjahraun, Þingvellir, Iceland. Bull Volcanol 74, 33–46 (2012). https://doi.org/10.1007/s00445-011-0480-1
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00445-011-0480-1