Gyali (Greek: Γυαλί "glass", also spelled Yiali or Yali) is a volcanic Greek island in the Dodecanese , located halfway between the south coast of Kos and Nisyros.
It consists of rhyolitic obsidian lava domes and pumice deposits.The island has two distinct segments, with the northeastern part almost entirely made of obsidian and the southwestern part of pumice. These are connected by a narrow isthmus and beach made of modern reef sediments.
GeographyGyali is the small island on the upper part of the picture.The island is 6 km (4 mi) long and between 4 km (2 mi) and 500 m (1,640 ft) across. It has a 180 m (591 ft) cave. The island is barren of vegetation. The 2001 census reported a resident population of 10 people. Administratively, it is part of the municipality of Nisyros.