Quantitative morphology, recent evolution, and future activity of the Kameni Islands volcano, Santorini, Greece

Abstract

Linking quantitative measurements of lava fl ow surface morphology with historical observations of eruptions is an important, but underexploited, route to understanding eruptions of silicic magma. We present here a new, high-resolution digital elevation model (DEM) for the intracaldera Kameni Islands, Santorini, Greece, which reveals the potential of high-resolution imaging (at ~1 m per pixel) of lava-fl ow fi elds by airborne light detection and ranging laser radar (LiDAR). The new DEM has an order-of-magnitude better resolution than earlier models, and reveals a wealth of surface morphological information on the dacite lava fl ows of the Kameni Islands. In turn, this provides quantitative constraints on the bulk rheology of the emplaced lava fl ows. When combined with a reanalysis of contemporary eruption accounts, these data yield important insights into the behavior of dacite magma during slow effusive eruptions on Santorini and elsewhere, and allow the development of forecasts for the style and duration of future eruptions. Kameni Island lava fl ows exhibit classic surface morphologies associated with viscous magma: levées and compression folds. Levée heights and fl ow widths are consistent with a Bingham rheology, and lava yield strengths of 3-7 × 104 Pa. Compression folds have long wavelengths (15-25 m), and change only a little downstream; this is consistent with observations of other terrestrial silicic lava fl ows. The blocky a'a dacite lava-fl ow margins show a scale-invariant morphology with a typical fractal dimension that is indistinguishable from basaltic Hawaiian a'a, confi rming that the fractal dimension is insensitive to the composition of the fl ow. Dome-growth rates during eruptions of the Kameni Islands in 1866 and 1939 are consistent with a model of slow infl ation of a dome with a strong crust. Lava domes on the Kameni Islands have a crustal yield strength (4 × 107 Pa) that is lower by a factor of 2-4 than the domes at Pinatubo and Mount St. Helens. The dome-height model combined with the apparent time-predictable nature of volcanic eruptions of the Kameni Islands allow us to suggest that should an eruption occur during 2006, it will last for more than 2.7 yr and produce a dome ~115-125 m high. © 2006 Geological Society of America.