The Dangers of Anydros

Anydros (Άνυδρος) is a privately owned, uninhabited Greek islet, in the municipality of Santorini. It lies to the northeast of Kolumbo, the feared underwater volcano.

The Greek occasionally call the island Amorgopoúla (Αμοργοπούλα): Amorgos is a larger island (also) situated to the northeast of Amorgopoúla. The suffix pôlos (πῶλος) means 'foal'. The Greek probably saw the smaller island as a foal to the horse which was Amorgos.

Anydros is a rocky, remote and inhospitable islet, and measures just 120 hectares. It has no permanent inhabitants since the 1860s. However, what it does hosts since 2025 is a seismometer, part of the Greek national network.

An earthquake fault located near Anydros was the source of the 1956 Amorgos earthquake that registered 7.6 on the Richter scale and caused widespread damage on Amorgos and the island of Santorini, situated just 55 kilometres to the southwest[1]. A second 7.5 quake and a 30-meter tsunami followed[2]. On Santorini, the earthquake demolished 529 houses and left many others damaged. A total of 53 people were killed as a result of the earthquake, with another three killed by the associated tsunami.

There were hundreds of minor earthquakes of up to magnitude 5 in an area around Anydros at the beginning of February 2025, causing concern in Santorini and causing more than half the population to leave the island. The seismic activity was attributed to tectonic plate movements rather than volcanism, and it was thought that it could last weeks.

[1] Papadimitriou et al: Seismicity Variations in the Southern Aegean, Greece, Before and After the Large (M7.7) 1956 Amorgos Earthquake Due to Evolving Stress in Pure and Applied Geophysics - 2005
[2] Okal et al: The 1956 earthquake and tsunami in Amorgos, Greece in Geophysical Journal International - 2009