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  • 1
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    Hierarchy of facies of pyroclastic flow deposits generated by Laacher See-type eruption (1985)
    GSA, Geological Society of America
    In:  Geology, 13 . pp. 278-281.
    Details
    Publication Date: 2017-04-06
    Description: The upper Quaternary pyroclastic flow deposits of Laacher See volcano show compositional and structural facies variations on four different scales: (1) eruptive units of pyroclastic flows, composed of many flow units; (2) depositional cycles of as many as five flow units; flow units containing (3) regional intraflow-unit facies; and (4) local intraflow-unit subfacies. These facies can be explained by successively overlapping processes beginning in the magma column and ending with final deposition. The pyroclastic flow deposits thus reflect major aspects of the eruptive history of Laacher See volcano: (a) drastic changes in eruptive mechanism due to increasing access of water to the magma chamber and (b) change in chemical composition and crystal and gas content as evacuation of a compositionally zoned magma column progressed. The four scales of facies result from four successive sets of processes: (1) differentiation in the magma column and external factors governing the mechanism of eruption; (2) temporal variations of factors inducing eruption column collapse; (3) physical conditions in the eruption column and the way in which its collapse proceeds; and (4) interplay of flow-inherent and morphology-induced transport mechanics.
    Type: Article , PeerReviewed
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  • 2
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    A detection of Milankovitch frequencies in global volcanic activity (2013)
    GSA, Geological Society of America
    In:  Geology, 41 (2). pp. 227-230.
    Details
    Publication Date: 2019-09-23
    Description: A rigorous detection of Milankovitch periodicities in volcanic output across the Pleistocene-Holocene ice age has remained elusive. We report on a spectral analysis of a large number of well-preserved ash plume deposits recorded in marine sediments along the Pacific Ring of Fire. Our analysis yields a statistically significant detection of a spectral peak at the obliquity period. We propose that this variability in volcanic activity results from crustal stress changes associated with ice age mass redistribution. In particular, increased volcanism lags behind the highest rate of increasing eustatic sea level (decreasing global ice volume) by 4.0 ± 3.6 k.y. and correlates with numerical predictions of stress changes at volcanically active sites. These results support the presence of a causal link between variations in ice age climate, continental stress field, and volcanism.
    Type: Article , PeerReviewed
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  • 3
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    Energy growth in laharic mass flows (2012)
    GSA, Geological Society of America
    In:  Geology, 40 (5). pp. 475-478.
    Details
    Publication Date: 2017-05-17
    Description: Lahars, debris flows, and sediment-rich floods are frequent and deadly hazards at all mountain-forming volcanoes. Their hazard potential is traditionally assessed through mass-conserving closed-system models, where peak conversion rates of potential energy to mechanical energy and hence maximum destruction potential are predicted to occur on the steepest volcano flanks. This belies evidence of extremely high-energy and deadly catastrophes caused by such flows at large distances from volcanoes. Here we use the first high-resolution record of a moving lahar to develop a new model of the temporally and spatially variable mass-flow structure. We show that bulk flow energy can grow dramatically in such systems over tens to hundreds of kilometers via momentum transfers from the lahar into water and particles along its path. We also demonstrate that dynamic transformations of such flows and their ultimate runout are primarily controlled by the mass flow front.
    Type: Article , PeerReviewed
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