View of the 13x8km large caldera of Santorini, Greece, formed during several Plinian eruptions including the Minoan eruption around 1613 BC. Öraefajökull volcano, SE-Iceland. The summit caldera of this large, explosive volcano that erupted last in 1728, is occupied by a glacier, which is part of the Vatnajökull ice cap that covers most of SE Iceland.