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Impact of hydrothermal activity on the geomorphology of the Nisyros intra-caldera region

Daniel Müller1 , Elisavet Nikoli2, Moritz Lang3, Alina Shevchenko1, Thomas R. Walter1, Paraskevi Nomikou2, Thor Hansteen4, Tom Kwasnitschka4

  • Affiliations: 1 GFZ Helmholtz Centre For Geosciences, Potsdam, Germany; 2 National & Kapodistrian University of Athens, Athens, Greece; 3 RWTH Aachen University, Aachen, Germany; ^4 ^Geomar Hemlmholtz Centre For Ocean Research, Kiel, Germany

  • Presentation type: Talk

  • Presentation time: Thursday 14:30 - 14:45, Room R290

  • Programme No: 3.8.6

  • Theme 3 > Session 8

Abstract

Hydrothermal activity and alteration can lead to mechanical weakening of volcanic rocks, decreased edifice stability, or increased erosion. Reversely, weakened zones such as faults can lead to localized hydrothermal alteration effects, so that a two-way interaction may be evident. A better understanding of these processes and interactions is particularly important in volcanic island environments due to the potential risk of slope failure and tsunami generation. To better investigate this, we analyze the hydrothermal system of Nisyros aiming to discriminate the relations between local faulting and the shallow hydrothermal system and to quantify the impact of the hydrothermal activity. We find that present hydrothermal eruptive centers indicate an interplay between shallow hydrothermal aquifers and fault orientations. Aligned sinkholes in the Lofos-Polivotis-Flegethron Complex (LPFC) indicate enhanced alteration and subsurface erosion over buried fault segments. Aligned sediment expulsion sites and vent-like deformation structures indicate liquefaction processes along the fault trends. Also in the main explosion crater wall (Stefanos crater) we find indications for local fault slip, oriented in azimuth of the main tectonic trend (NE-SW). However, a rotation of the main surface ruptures of the 2001 earthquakes within the Lakki plain and alignments of small-scale features perpendicular to the tectonic trend suggest additional importance of intersecting faults on the activity pattern. An unstable flank appears to be controlled by the mutual effects of local faulting and hydrothermal activity. We combine our observations and give an overview of the dynamics and impact of the hydrothermal system in the intra-caldera region of Nisyros.