The area of Velebit is a pronounced karst area with special geomorphologic and hydrologic features. The largest part of the Nature Park is covered by Jurassic limestone whereas smaller or larger areas are somewhere under Pleistocene or Paleogene and to a lesser extent Holocene deposits. The oldest rocks, dating from the Middle and Upper Carboniferous can be found near Brušan, Divoselo and Počitelj on Velebit’s northeast side.
Apart from the base structure, Velebit’s relief was also affected by tectonic movements during geological history which resulted in faults shaping the global relief. In late geological periods such base was also affected by other natural factors resulting in the abundance of karst forms such as grikes, sinkholes, solution pans, crags and columns, as well as speleological forms such as caves, caverns and pits. Karst depressions, so called dulibe or padeži, also contribute to relief diversity.
Due to their outstanding geomorphological specificities, specially protected parts of nature in the area of the Nature Park are: important landscape Zavratnica, geomorphological natural monument Cerovac caves and paleontological natural monument Velnačka glavica.