Volcanic activity is then restricted to the eastern Aegean, between Samos and Kos, from 10.7 to 5.6 Ma. Only in Patmos does volcanic activity reach up to 3.5 Ma. Volcanic and sub – volcanic rocks are present to a minor extent in
Samos and Kos. Kalogeroi, a rocky islet between Andros and Chios, is exclusively made up of underwater basalts. Patmos is almost exclusively built from volcanic rocks.