Geology and the conservation of antique monuments in Turkey

Abstract

This article deals with a geological investigation carried out as a fundamental part of the conservation and static restoration of several antique churches excavated in andesitic tuff in the Göreme valley and adjacent areas of Cappadocia in Central Anatolia, Turkey. Two stages have been completed already, in 1982 and 1985, respectively, and the work is still in progress.

Seismicity is not regarded as a structural hazard, but the geological history includes a series of volcanic episodes since the Oligocene (about 38 million years ago), which persisted into fairly recent times and laid down a great thickness of tuff rock. Erosion sculptured this tuff preferentially because of irregular harder, basaltic layers, which later capped rock pinnacles, the so-called peribacalars, in which churches were hewn over a thousand years ago.

Because the host rock is heavily fissured, precipitation has entered and has damaged many mural paintings. These are also subject to vandalism, and efforts have been made to restore them by the usual conservation intervention. However, grouting is necessary and must take into account the porosity of the tuff, which also permits capillary rise from crypts. Sometimes, during wet episodes, water flushes into these and scours the interior walls as well. The basic problem remains geological, and the contribution of the earth sciences is very important. Thus, an engineering geology study has determined that the tuff rock is suitable both for building retaining walls and acting as a constituent in cement grout. It is expected that the UNESCO/ICCROM program to save the churches will be completed successfully within the next five years or so.