The Nisyros Hydrothermal Crater Field

The Nisyros Hydrothermal Crater Field
Fumarolic Activity
The Nisyros Hydrothermal System

Fumarolic Activity

Two types of fumarolic activity occur within the caldera crater field: 1. Degassing and steaming mud pools are present in the central parts of Stefanos and Polybotis craters. They vary in size from a few centimetres to a meter in diameter and are the results of boiling and steam condensation from the uppermost level of the upper hydrothermal cell.

Their activity is influenced by the seasonal rainfall and humidity. The gases with temperatures close to 100°C are rich in H₂O, H₂S, CO₂, H₂ and CH₄. The boiling muddy waters are rich in sulfuric acid, with a pH between 1.5 and 3.

2. The second type of fumaroles is bound to disseminated channels and fissures within the walls and rims of the craters as well as along major fracture zones. The gases with temperatures of a few degrees below or close to 100°C are also rich in H₂O, CO₂, H₂, H₂S, and CH₄. They seem to originate from the deeper parts of the hydrothermal system.

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