The Hanish Islands are formed from a series of volcanic vents along a NE-SW trend, and include the Holocene Great Hanish, Little Hanish, and many other small islands and submarine shoals.  The Zukur-Hanish island group, in contrast to other Red Sea islands such as Jebel at Tair or the Zubair Islands, lies in shallow waters south of the Red Sea median trough. Spatter cones, cinder cones, and ash cones line the crest of the 20-km-long Great Hanish island.  Short lava flows reach the coast on both sides of the island.  As with the Zukur group to the north, initial eruptions were phreatic.  Subsequently basaltic cinder cones were formed, and spatter cones produced fluid lava flows.