Gebel Umm Shaumar (2,586 m), Gebel El Thabt (2,439 m), Mt. Sinai (Gebel Musa) (2,2,80 m) and Gebel Serbal (2,070 m). These mountains are composed of rocks of various types, colours and ages; for instance Gebel Katherine is made of andesite porphyry, a volcanic rock about ten million years old.