10 research outputs found
Volcanism of the South Aegean Volcanic Arc
Volcanism along the South Aegean Volcanic Arc began about 4.7 Ma and has lasted until the present day, with eruptions at Methana, Milos, Santorini, Kolumbo and Nisyros Volcanoes in historical times. These volcanoes can be grouped into five volcanic fields: three western fields of small, mostly monogenetic edifices, and two central/eastern fields with composite cones and calderas that have produced large explosive eruptions. Crustal tectonics exerts a strong control over the locations of edifices and vents at all five volcanic fields. Tephra and cryptotephra layers in deep-marine sediments preserve a continuous record of arc volcanism in the Aegean as far back as 200,000 years. Hazards from the volcanoes include high ash plumes, pyroclastic flows and tsunamis. Monitoring networks should be improved and expanded
Active hydrothermal fluids circulation triggering small-scale collapse events: the case of the 2001–2002 fissure in the Lakki Plain (Nisyros Island, Aegean Sea, Greece)
In 2001–2002, two ground collapses occurred in the island of Nisyros (Aegean
Sea, Greece), which formed a 600 m long and up to 5 m wide fissure in the vegetated
central part of the Lakki Plain caldera. The fissure was alternatively ascribed to tensional
stress release and hydrothermal alteration. In this study, we present original data of diffuse
CO2 soil fluxes, soil temperatures, mineralogical and chemical composition of the calderafilling
deposits exposed on the fissure walls, and chemical and isotopic composition of
interstitial soil gases collected from: the bottom of the fissure, the adjacent vegetated areas, the hydrothermal craters, and selected sites outside the caldera. The occurrence of intense
hydrothermal alteration was shown by both mineralogical and chemical analyses of the
fissure walls material. Typical mineral assemblage and enrichments in incompatible elements
related to advanced argillic alteration, characterizing steam-heated hydrothermal
environments, were recognized. Although the low-permeable sediment cover in the Lakki
Plain concealed the underneath hydrothermal gas flow, preventing anomalous soil temperatures
and CO2 fluxes, the chemical and isotopic composition of the interstitial soil
gases revealed an active hydrothermal fluids circulation below the collapsed area, likely
controlled by buried structural lineaments. Hydrothermal alteration can then be invoked as
the most likely trigger mechanism for the 2001–2002 collapse event
Active hydrothermal fluids circulation triggering small-scale collapse events: the case of the 2001–2002 fissure in the Lakki Plain (Nisyros Island, Aegean Sea, Greece)
In 2001–2002, two ground collapses occurred in the island of Nisyros (Aegean
Sea, Greece), which formed a 600 m long and up to 5 m wide fissure in the vegetated
central part of the Lakki Plain caldera. The fissure was alternatively ascribed to tensional
stress release and hydrothermal alteration. In this study, we present original data of diffuse
CO2 soil fluxes, soil temperatures, mineralogical and chemical composition of the calderafilling
deposits exposed on the fissure walls, and chemical and isotopic composition of
interstitial soil gases collected from: the bottom of the fissure, the adjacent vegetated areas, the hydrothermal craters, and selected sites outside the caldera. The occurrence of intense
hydrothermal alteration was shown by both mineralogical and chemical analyses of the
fissure walls material. Typical mineral assemblage and enrichments in incompatible elements
related to advanced argillic alteration, characterizing steam-heated hydrothermal
environments, were recognized. Although the low-permeable sediment cover in the Lakki
Plain concealed the underneath hydrothermal gas flow, preventing anomalous soil temperatures
and CO2 fluxes, the chemical and isotopic composition of the interstitial soil
gases revealed an active hydrothermal fluids circulation below the collapsed area, likely
controlled by buried structural lineaments. Hydrothermal alteration can then be invoked as
the most likely trigger mechanism for the 2001–2002 collapse event