KPSS 2007 Soru=42

We see from the passage that Hierapolis was abandoned in the 14th century due to ----.

The ruins of Hierapolis, a once-grand city near
modern Denizli in Turkey, brilliantly bring into being a
picture of life in the early centuries of the modern era.
It was here that the mix of pagan, Roman, Jewish
and early Christian elements evolved into a distinctly
Anatolian environment. Founded around 190 B.C. by
Eumenes II, King of Pergamum, Hierapolis was a
cure centre that grew wealthy under the Romans and
even more so under the Byzantines. It had a large
Jewish community and an early Christian church.
Frequent earthquakes regularly brought disaster;
after the one in 1334, the locals finally gave up and
moved away. Near the Hierapolis Archaeology
Museum stand the ruined foundations of a Temple of
Apollo. This temple had a spring called the Plutonium
dedicated to Pluto, Roman god of the underworld.
The spring gives off toxic vapours, and the temple
priests would demonstrate its powers to visitors by
throwing in small animals and birds and watching
them die.