Observations on the structure of Surtsey

New insights into the subsurface structure of Surtsey, an Icelandic volcanic island, challenge previous understandings of its geothermal dynamics. Analysis of 2017 cored boreholes reveals that near-surface layering dips westerly, indicating the boreholes are within the Surtur crater, and suggests a broad diatreme underlies the vent. Temperature measurements in these boreholes show peak temperatures of 124–127 °C at depths of 105–115 meters below the surface, with residual heat detected up to 290 meters depth, implying a broad, warm substrate rather than localized intrusions. This challenges the earlier hypothesis of a nearby intrusion as the source of the heat anomaly and instead supports a model where heat was conducted from a hot lava shield into a diatreme, creating a vapor-dominated system below sea level.

Moore, J. C., & Jackson, M. D. (2020). Observations on the structure of Surtsey. Surtsey Research, 14, 33–45. https://doi.org/10.33112/surtsey.14.3