The area exhibits karst morphology , with bedrock largely consisting of limestones and comparatively small areas of dolomites and Quaternary sediments . Eocene flysch forms the southwest boundary of the catchment area , towards which the catchment basin drains and where the Ombla rises . The rocks were formed as a thick series of carbonate sediments were deposited between the Norian and Late Cretaceous as the Adriatic Carbonate Platform , up to deep . In the Eocene and early Oligocene , the Adriatic Plate moved north and north-east , contributing to the Alpine orogeny via the tectonic uplift of the Dinarides . The basin 's karst topography developed from the carbonate platform 's exposure to weathering . Karstification largely began after the Dinarides ' final uplift in the Oligocene and the Miocene , when the carbonates were exposed to atmospheric effects ; this extended to the level of below the present sea level , exposed during the Last Glacial Maximum . Some karst formations were created during earlier sea level drops , most notably the Messinian salinity crisis . The geological structure of the area indicates recent tectonic activity in the catchment , with a fault running between Hum and the Ombla . A recent strong earthquake in the wider region was the 1979 Montenegro earthquake , measuring 7.0 on the Richter scale . The only strong historical earthquake in the immediate area was the 1667 Dubrovnik earthquake , which was followed by a tsunami
1979 Montenegro earthquake
1979 Montenegro earthquake
Ombla