At the southern end of Thirasia there is one of the most impressing volcanic veins of Santorini Kaldera. It is actually a vertical intrusion of lava into the flows of earlier veins. Most probably the volcanic material penetrated the fault surface. The vein is even more impressive, because thanks to the erosion of the surrounding materials it stands out looking like a small wall.
* Source: Atlas of the Geological Monuments of the Aegean/ Published by the Ministry for the Aegean, 2002, www.ypai.gr