Temperature and Conductivity as Indicators of the Morphology and Activity of a Submarine Volcano: Avyssos (Nisyros) in the South Aegean Sea, Greece

Evangelos Bakalis,Theo Mertzimekis,Francesco Zerbetto,Paraskevi Nomikou

doi:10.3390/geosciences8060193

Evangelos Bakalis, Theo Mertzimekis + Show 2 more

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https://doi.org/10.3390/geosciences8060193

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Abstract

The morphology and the activity of a submarine caldera, Avyssos, at the northern part of Nisyros volcano in the South Aegean Sea (Greece), has been studied by means of remotely-operated underwater vehicle dives. The recorded time series of temperature and conductivity over the submarine volcano have been analyzed in terms of the generalized moments method. The findings of the mathematical analysis shed light on the volcanic activity, but also on the morphology (shape) of the submarine volcano. The conductivity time series indicates that the volcano is at rest, in agreement with other types of observations. On the other hand, temperature fluctuations, which in general describe a multifractal process, show that the submarine caldera operates as an open system that interacts with its surroundings. This type of analysis can be used as an indicator for the state of activity and the morphological structure (closed or open system) of a submarine volcano.

Highlights

Nisyros island is an active volcano at the eastern edge of the Aegean within the Hellenic Volcanic arc and trench system along the convergence zone of the Eurasian and African plates [1,2]
Analyzing the recorded time series of temperature and conductivity just above the Avyssos submarine volcano, we found that (a) the volcano was at rest and there was no activity in terms of emerging gases and ionic particles and (b) the temperature presented an initial multiplicative behavior reflecting the mixing of at least two different random processes, which turns to be stationarity
We propose the above methodology of analysis as an indicator for the state of activity and the shape of a submarine volcano featuring a volcanic field

Summary

Introduction

Nisyros island is an active volcano at the eastern edge of the Aegean within the Hellenic Volcanic arc and trench system along the convergence zone of the Eurasian and African plates [1,2]. Nisyros and explored the volcanic field offshore of the island, mainly along the Nisyros-Yali-Strongyli area [8]. Such information is available for the neighboring Avyssos underwater caldera (see Figure 1). A dedicated cruise in the 2010 campaign focused on exploring the unknown volcano-tectonic characteristics of the Nisyros-Yali-Kos region and the associated volcanic field around Nisyros. Both Nisyros and Santorini belong to the same volcanic arc; both have exhibited unrest in the recent past [4,13], and Geosciences 2018, 8, 193; doi:10.3390/geosciences8060193 www.mdpi.com/journal/geosciences

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