The northern rim of the Mellieha ridge is characterised by an alternation of elevated plateaux (including Il-Qortin and Il-Qortin ta' Ghajn Zejtuna) and deeply incised valleys such as Il-Wied ta' Ruman. The abrupt interface between the various ridges and valleys is displayed as a sheer inland cliff underlain by steep boulder screes formed by mass movements in the Blue Clay and Upper Coralline Limestone. This landform also contains numerous caves eroded naturally out of their Upper Coralline Limestone component.

The large-scale geomorphological processes that have formed the cliff system and caves have resulted in a prominently steep and rugged topography that is among the scenic highlights of northern Malta.

The geomorphology and supporting ecosystem processes are mainly concentrated on the vertical or steeply sloping cliff face and on the underlying slopes and boulder screes together with the overlying cliff top garigue.

MEPA scheduled Tas-Sellum inland cliffs and caves as a Level 2 Area of Ecological Importance as per Government Notice No. 681/00 in the Government Gazette dated 25 August 2000.