Tendürek Dagi, also known as Tendürük Dagi, is an elongated shield volcano that rises 1800 m above the plain of Dogubayazit, near the Iranian border, south of Mount Ararat. An E-W-trending summit ridge, developed north of an arcuate caldera structure exposed only on the southern side, contains two well-developed cones. The higher western cone is capped by a steep-walled crater with a trachytic spine at its eastern edge. The flatter eastern crater contains a warm lake. The shield volcano developed during a period when highly mobile lava flows from the western crater covered an area of 500 sq km. Following summit caldera formation, numerous flank eruptions took place from N-S-trending fissures, producing viscous trachytic lava domes and flows as well as fluid basaltic pahoehoe flows that extend 10-20 km to the north and south. The latest activity formed two major basaltic lava flows from large cones on the NE and SE flanks. An eruption took place from a vent on the SE flank about 2500 years ago, and a gas-and-ash eruption took place in 1855.