Volcanic rocks, predominantly serpentinite and diorite are apparent in the Muscat area and extend along the Gulf of Oman coast for ten or twelve  from the district of Darsait to Yiti. Plutonic rocks constitute the hills and mountains of Muscat and span approximately  from Darsait to Ras Jissah. These igneous rocks consists of serpentinite, greenstone, and basalt, typical of rocks in southeastern regions of the Arabian Peninsula. South of Muscat, the volcanic rock strata are broken up and distorted, rising to a maximum height of  in Al-Dakhiliyah, a region which includes Jebel Akhdar, the country's highest range. The hills in Muscat are mostly devoid of vegetation but are rich in iron.