The island is part of a chain of mountains from which it became separated after earthquakes and subsidence that occurred in ancient times. These mountains include Kalymnos and Kappari which are separated by an underwater chasm c. 70 meters 230 ft) (40 fathoms deep), as well as the volcano of Nisyros and the surrounding islands.
There is a wide variety of rocks in Kos which is related to its geographical formation. Prominent among these are the Quaternary layers in which the fossil remains of mammals such as horses, hippopotami and elephants have been found. The fossilized molar of an elephant of gigantic proportions was presented to the Paleontology Museum of the University of Athens.
Kos, Greece 