Pachia is a volcanic islet to the west of Nisyros.
It features basal dacitic lavas overlain by two pumice sequences of the Kos Plateau Tuff unit that, as its name suggests, originated from a violent series of eruptions from nearby Kos island (the most voluminous eruption in the Eastern Mediterranean that took place 161000 years ago). Out of these, the lower features sedimentary structures that are interpreted as depositions from surge pyroclastic density currents in sandwave phases, and the upper consists of lapilli tuff with lithic blocks. However, the highest elevation part of the islet is covered by a thin layer of ash and fallout lapilli, with an interbedded paleosol, that may be correlated with an eruptive cycle of the Nisyros Composite Stratovolcano eruptive cycle.
