Aspronisi ( Greek : Ασπρονήσι ) is an uninhabited island lying within the Santorini caldera . The island was originally formed by the massive Minoan eruption in the 2nd millennium BC , after which it was gradually built up by successive volcanic activity . The name Aspronisi , which means ' White Island ' in Greek , is derived from the island being partially composed of white pumice . Aspronisi was formed through the gradual volcanic activity in the Santorini caldera , which itself is composed of four distinct shield volcanoes . The island was formed along with the current Santori caldera during a massive eruption in the 2nd millennium BC that expelled 14 cubic miles ( 60 km3 ) of dense rock . Aspronisi was briefly a submarine volcano before the force of the eruption pushed the islet above the surface , after which dense layers of pumice and tephra ejected from the volcano covered the island . These deposits eventually solidified into the pale white deposits that give Aspronisi it 's moniker of the " White Isle " . The base of the island is composed of black lava rock , and the island is connected to the larger islands of Therasia and Santorini by the submerged outer edge of the Santorini caldera
Minoan eruption
Minoan eruption
Aspronisi