The Hierapolis-Pamukkale Archaeological and Geosite, Southwest Turkey

Abstract

The Hierapolis-Pamukkale archaeological and geosite is located near Denizli in southwest Turkey. The site was awarded UNESCO World Heritage status in 1988 and receives more than 2.5 million visitors annually. The translation of Pamukkale is “Cotton Castle”, an apt description of the white deposits of travertine that are so extensive they form an extensive ridge. Travertine is a hard, compact variety of limestone deposited from hot springs or geothermal waters. The ancient city of Hierapolis is situated on the crest of the travertine ridge and was originally built as a Greek colony in the 2ndC BC. The city was enlarged during the Roman Empire and became an important spa and burial ground. The archaeological and historical data suggest the city had to be entirely rebuilt after the major earthquake of 60 AD and was abandoned after an earthquake in 1354 AD. The Hierapolis-Pamukkale site is located in the Denizli Basin, a significant feature of the Menderes Massif. The basin has developed where two large grabens intersect, the W–E trending Buyuk Menderes Graben and the NW–SE trending Alasehir Graben. Four main centres of active travertine deposition are recognized, the distribution of which is influenced by the NW–SE trending graben faults. The travertine deposits at the Hierapolis-Pamukkale site are associated with hot springs located on the Hierapolis Fault, a subsidiary feature of the regional Pamukkale fault system. The grabens are primarily Neogene features related to crustal extension and many of the faults in the Denizli Basin remain active. The basin is thermally active and the occurrence of hot springs and groundwater circulation through limestone bedrock is a key component in formation of the travertine. The upwelling hot waters are supersaturated in calcium carbonate. Seventeen hot water springs with temperatures ranging from 35 °C to 100 °C are currently active at Pamukkale. The deposition of the travertine is contemporaneous with recent fault activity and the deposits have a maximum age of 400,000 BP. Most of the travertine is younger than 60,000 BP. Five principal varieties of travertine are recognized at Pamukkale, the most abundant types of which are fissure-ridge and terrace-mound travertine. The fissure-ridge travertine forms the largest of the deposits and has been extensively quarried. The majority of the buildings and tombs at the Hierapolis archaeological site are built of either locally-derived marble or fissure-ridge travertine. Large blocks of white travertine were used in the Roman theatre for decorative purposes. Most of the sacred sites at Hierapolis were constructed directly above the active Hierapolis Fault. These include the Temple of Apollo and Plutonium. The site was probably chosen for the occurrence of natural gases associated with the thermal waters. Priests are thought to have deceived visitors by appearing to be immune to the toxic vapours. Historical legends in the region are linked to catastrophic earthquakes which may describe the major event of 60 AD. Movement on the fault zone at Hierapolis occurred during the Denizli Earthquake of 1965 and toxic gases, similar to those identified in the ancient Plutonium, are emitted from the rupture.