The Volcanic History

The Basal Volcanic Complex (ca. 160,000 to 100,000 years)
The Early Caldera Stratovolcano (ca. 100,000 to 30,000 years)
Lakki Pyroclastics and Avlaki Complex
Lacustrine and Pyroclastic Formations
The Melisseri - Evangelistra - Afionas Complex
The Emborios Complex
The Ellinika - Kyra - Lies Pyroclastic Complex
The Argos - Stavros Complex
The Main Caldera Formation (30,000 to 15,000 years ?)
The First Caldera Phase (?30,000 to 20,000 years ?)
The Second Caldera Phase (20,000 to <15,000 years ?)

The First Caldera Phase (?30,000 to 20,000 years ?)

The island of Nisyros had grown to a mature stratovolcano over a long time span, including a small central caldera and several satellite craters. It accumulated a large volume of magma at shallow depth of several kilometres. As the result, a hydrothermal system was generated, manifested by fumarolic activity in the craters.

After precursors of gas and steam explosions, a major "Plinian eruption" began to reach stratospheric heights. A huge volume of pyroclastic flows (glowing avalanches) and air-fall pumice ("the lower pumice") covered the entire island, and rhyolitic lavas then erupted towards the southeastern slopes of Nikia ("Nikia rhyolites").

Subsequently, a major collapse of the volcano followed, leaving behind a large caldera of 4 to 5 km in diameter and a depth of a few hundred meters.

After long period of volcanic quiescence and erosion, a second "Plinian" eruption produced the upper white pumice, which is the characteristic feature on the northern slope between Mandraki and Cape Katsuni.

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