In the late Miocene (about 10-7 million years ago) volcanoes deposited thick layers of ash across the Cappadocia region of central Turkey. The soft tuff alternates with more resistant layers of welded tuff, breccia, basaltic lava flows, and limestone. By the early Pliocene (5.4-4 million years ago) volcanism was localized to composite centers of basalt to rhyolite composition. In the mid-Pliocene (2.9 million years ago) extensive ash layers (ignimbrite) of the rhyodacitic Incesu/Valibaba Ignimbrite covered at least 300 square km and a large caldera (65 x 35 km) formed in eastern Cappadocia. All of these rocks accumulated in the Urgup basin. Erciyes Dag, a Holocene composite volcano, is located in the caldera. Stream erosion of the deposits has produced thousands of cones and towers up to 100 feet (30 m) in relief. All photos courtesy of Barbara Criddle.
From the 4th to the 13th century the soft rock of the cones was excavated to make churches and homes. Many continue to be used in the village of Urgup, 140 miles (225 km) southeast on Ankara.
Miocene-Pliocene volcanism in central Turkey was associated with the subduction of oceanic crust at the leading edge of the Afro-Arabian plate under the Anatolian micro-plate of the Eurasian Plate. To the west of the subduction zone, continental crust of the African Plate was colliding with the continental crust of the Anatolian micro-plate. Subduction led to the formation of two volcanic arcs. The African and Arabian plates are separated by the Dead Sea transform fault. Map simplified from Innocenti and others, 1975.
Sources of Information:
Amini, H., Stern, C.R., Erdogan, M., and Sengor, A.M.C., 1986, Late Cenozoic magmatic evolution of the Nevsehir-Kayseri area, Cappadocia, central Anatolia, Turkey: Geol. Soc. America Abstracts with Programs, v. 18, p. 526.
Innocenti, F., Mazzuoli, R., Pasquare, G., Radicati di Brozolo, F., and Villari, L., 1975, The Neogene calcalkaline volcanism of central Anatolia: geochronological data on Kayseri-Nigde area: Geol. Mag., v. 122, p. 349-360.
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