New insights into volcanic activity from strain and other deformation data for the Hekla 2000 eruption

Abstract 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 magma geometry by using a wide variety of deformation data: campaign GPS; an InSAR interferogram; dry tilt data, and borehole strain data. The dike that causes surface fissuring extends no more than ~ 0.5 km in depth, and the reservoir depth is ~ 10 km. These are connected by a conduit of small lateral extent. Data for previous eruptions are consistent with this model. We propose that the marked change in eruption interval is because this conduit remains liquid during the short interval between recent eruptions; only a small pressure increase is required to rupture the thin crustal seal. Such a state is consistent with precursory seismicity being confined to very shallow depths and may be applicable to other volcanoes that undergo abrupt changes in eruption interval.

[1]  Agust Gudmundsson,et al.  Effect of local and regional stress fields on sheet emplacement in West Iceland , 1992 .

[2]  Daniel Dzurisin,et al.  Volcano deformation : geodetic monitoring techniques , 2007 .

[3]  Tom Simkin,et al.  Volcanoes of the World , 2011 .

[4]  P. Einarsson,et al.  The Hekla eruption 1980–1981 , 1983 .

[5]  Kristín S. Vogfjörð,et al.  The millennium eruption of Hekla in February 2000 , 2007 .

[6]  P. Einarsson,et al.  Seismic constraints on magma chambers at Hekla and Torfajökull volcanoes, Iceland , 2004 .

[7]  K. Gronvold,et al.  Location of a magma reservoir beneath Hekla Volcano, Iceland , 1983, Nature.

[8]  K. Ágústsson,et al.  Mechanism of the 1991 eruption of Hekla from continuous borehole strain monitoring , 1993, Nature.

[9]  F. Sigmundsson,et al.  Magma chamber deflation recorded by the global positioning system: The Hekla 1991 Eruption , 1992 .

[10]  P. Einarsson,et al.  Seismic activity related to the 2000 eruption of the Hekla volcano, Iceland , 2005 .

[11]  K. Mogi.  Relations between the Eruptions of Various Volcanoes and the Deformations of the Ground Surfaces around them , 1958 .

[12]  Y. Okada.  Surface deformation due to shear and tensile faults in a half-space , 1985 .

[13]  P. Einarsson,et al.  Earthquake activity related to the 1991 eruption of the Hekla volcano, Iceland , 2002 .

[14]  S. Pórarinsson.  The Eruptions of Hekla in historical times : a tephrochronological study , 1967 .

[15]  E. Tryggvason.  Observed ground deformation at Hekla, Iceland prior to and during the eruptions of 1970, 1980 1981 and 1991 , 1994 .

[16]  S. Thorarinsson,et al.  The Hekla Eruption of 1970 , 1972 .

[17]  S. Gíslason,et al.  The 1991 eruption of Hekla, Iceland , 1992 .

[18]  William I. Rose,et al.  Weather radar observations of the Hekla 2000 eruption cloud, Iceland , 2004 .

[19]  Freysteinn Sigmundsson,et al.  Deep magma storage at Hekla volcano, Iceland, revealed by InSAR time series analysis , 2011 .

[20]  A. Rubin.  Getting granite dikes out of the source region , 1995 .

[21]  James H. Dieterich,et al.  Deformation from Inflation of a Dipping Finite Prolate Spheroid in an Elastic Half‐Space as a Model for Volcanic Stressing , 1988 .

[22]  Freysteinn Sigmundsson,et al.  Volcano deformation at active plate boundaries: Deep magma accumulation at Hekla volcano and plate boundary deformation in south Iceland , 2012 .