The volcanoseismic crisis of 1996–97 in Nisyros, SE Aegean Sea, Greece

Papadopoulos, Vassilios; Sachpazi,; Panopoulou,; Stavrakakis,

doi:10.1046/j.1365-3121.1998.00184.x

Cited by 54 publications

(43 citation statements)

References 9 publications

(10 reference statements)

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“…The Stefanos crater was chosen for our study because of a recent increase in fumarole activity and outflow of melted sulfur and hot mud (Papadopoulos et al, 1998;Chiodini et al, 2002;Sachpazi et al, 2002;Vougioukalakis and Fytikas, 2005;Lagios et al, 2007), as well as its strong thermal signature in comparison to other phreatic craters (Lagios et al, 2007;Ganas et al, 2010). Moreover, our results may have implications relevant for other sites.…”

Section: Discussionmentioning

confidence: 96%

“…1). This volcanic island has a long history of phreatic eruptions, the latest in 1871-1873 and 1887 , experiencing an episode of unrest in 1996-2001 (Papadopoulos et al, 1998;Chiodini et al, 2002;Sachpazi et al, 2002). The Stefanos crater is one of several phreatic craters on Nisyros, and is also the major contributor to the total heat budget of the island (Lagios et al, 2007;Ganas et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

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The ring-shaped thermal field of Stefanos crater, Nisyros Island: a conceptual model

Pantaleo

Walter

2014

Solid Earth

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Abstract. Fumarole fields related to hydrothermal processes release the heat of the underground through permeable pathways. Thermal changes, therefore, are likely to depend also on the size and permeability variation of these pathways. There may be different explanations for the observed permeability changes, such as fault control, lithology, weathering/alteration, heterogeneous sediment accumulation/erosion and physical changes of the fluids (e.g., temperature and viscosity). A common difficulty, however, in surface temperature field studies at active volcanoes is that the parameters controlling the ascending routes of fluids are poorly constrained in general. Here we analyze the crater of Stefanos, Nisyros (Greece), and highlight complexities in the spatial pattern of the fumarole field related to permeability conditions. We combine high-resolution infrared mosaics and grain-size analysis of soils, aiming to elaborate parameters controlling the appearance of the fumarole field. We find a ring-shaped thermal field located within the explosion crater, which we interpret to reflect near-surface contrasts of the soil granulometry and volcanotectonic history at depth. We develop a conceptual model of how the ring-shaped thermal field formed at the Stefanos crater and similarly at other volcanic edifices, highlighting the importance of local permeability contrast that may increase or decrease the thermal fluid flux.

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Section: Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

The ring-shaped thermal field of Stefanos crater, Nisyros Island: a conceptual model

Pantaleo

Walter

2014

Solid Earth

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“…During this period, more than 1600 earthquakes occurred (Papadopoulos et al, 1998). Sachpazi et al (2002) suggest that these events were compatible with the intrusion of a magmatic body at shallow depth within the crust of the Nisyros region, rather than being attributed to regional tectonic motions.…”

Section: A Brief Summary Of the Geological Evolution Of Nisyros And Tmentioning

confidence: 88%

“…In 1996-1998, Nisyros showed signs of unrest with a seismic crisis accompanied by intense ground deformation and increased activity and geochemical variations of the island's fumaroles (Papadopoulos et al, 1998;Sachpazi et al, 2002;Lagios et al, 2005;Caliro et al, 2005). During this period, more than 1600 earthquakes occurred (Papadopoulos et al, 1998).…”

Section: A Brief Summary Of the Geological Evolution Of Nisyros And Tmentioning

confidence: 99%

“…Historically, there have been 13 phreatic eruptions in the caldera, most recently during 1871-1873 and in 1888 . More recently, in 1996More recently, in -1998, Nisyros experienced a volcano-seismic crisis, accompanied by ground uplift of more than 10 cm, indicating a period of unrest (Papadopoulos et al, 1998). Nisyros volcano presents an opportunity to study the threat posed by a relatively small volcano situated in an arc-island setting in both Europe and a region of significant seasonal population exposure.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of volcanic threat from Nisyros Island, Greece, with implications for aviation and population exposure

Kinvig

Winson

Gottsmann

2010

Nat. Hazards Earth Syst. Sci.

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Abstract. Nisyros island in the South Aegean volcanic arc, Greece, is a Quaternary composite volcano with a 3.8 km wide caldera that in 1996 entered a volcano-seismic crisis, which heralded the islands' return to a state of unrest. The caldera has been the locus of at least thirteen phreatic eruptions in historical times, the most recent in 1888, and the system is still presently affected by considerable hydrothermal activity. Although the recent unrest waned off without eruption, there are still open questions relating to the current threat of volcanic activity from the island. Here, we perform a detailed and systematic assessment of the volcanic threat of Nisyros using a threat analysis protocol established as part of the USGS National Volcano Early Warning System (NVEWS). The evaluation involves a methodical assessment of fifteen hazard and exposure factors, and is based on a score system, whereby the higher the score, the higher the threat is. Uncertainty in assessment criteria are expressed by allowing for a conservative and an extreme score for each factor. We draw our analysis from published data as well as from results of our research on Nisyros over the past years. Our analysis yields a conservative threat score of 163 and an extreme score of 262. The most adverse exposure factors include significant scores relating to aviation and population exposure to volcanic hazards from Nisyros. When looked at in comparison to US volcanoes both scores place Nisyros in the "Very High Threat (VHT)" category, grouping it with volcanoes such as Redoubt, Mount Ranier and Crater Lake. We identify a short-fall in recommended surveillance efforts for VHT volcanoes given existing monitoring capabilities on the island. We discuss potential pitfalls of applying the NVEWS scheme to Nisyros and suggest potential adaptaCorrespondence to: J. Gottsmann (j.gottsmann@bristol.ac.uk) tion of analysis scheme to match industrial and societal conditions in Europe. At the same time, our findings indicate that that volcanic threat posed by Nisyros volcano may currently be underestimated.

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An overview of recent (1988 to 2014) caldera unrest: Knowledge and perspectives

Acocella

Lorenzo

Newhall³

et al. 2015

Reviews of Geophysics

155

165

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Calderas are among the most active and dangerous volcanoes. Caldera unrest is defined by enhanced seismicity, gravity changes, surface deformation, and degassing. Although much caldera unrest does not lead to an eruption, every eruption is preceded by an unrest episode. Therefore, the proper description of unrest and the forecast of its possible outcome is a timely and challenging task. Here we review the best known unrest at calderas from 1988 to 2014, building on previous work and proposing an updated database. Where established, the root cause for unrest is always magmatic; none was purely hydrothermal or tectonic. An interpretive classification of unrest invokes two spectra-compositional (mafic to felsic) and the state of magma conduits feeding from the magma reservoir(s) to the surface (from fully plugged, through semiplugged, to open). Magma and gas in open conduits can rise and erupt freely; magma in semiplugged conduits erupts less frequently yet still allows some gas to escape; plugged conduits allow neither magma nor gas to escape. Unrest in mafic calderas is subtler, less pronounced, and repeated, especially with open systems, ensuring the continuous, aseismic, and moderate release of magma. Plugged felsic calderas erupt infrequently, anticipated by isolated, short and seismically active unrest. Semiplugged felsic calderas also erupt infrequently and are restless over decades or centuries, with uplift, seismicity, and degassing and, on the longer-term, resurgence, suggesting repeated stalled intrusions. Finally, the expected advances in better understanding caldera unrest are discussed.

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The volcanoseismic crisis of 1996–97 in Nisyros, SE Aegean Sea, Greece

Cited by 54 publications

References 9 publications

The ring-shaped thermal field of Stefanos crater, Nisyros Island: a conceptual model

The ring-shaped thermal field of Stefanos crater, Nisyros Island: a conceptual model

Analysis of volcanic threat from Nisyros Island, Greece, with implications for aviation and population exposure

An overview of recent (1988 to 2014) caldera unrest: Knowledge and perspectives

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