Geologically, Jordan lies on the Arab shield, which for the most part consists of bedrock rocks. Above these are fossil-bearing Cambrian strata, and above these, substantial chalk and tertiary limestones. Lime layers from chalk contain phosphate layers, regional basalt portions from volcanic eruptions occur. Active fault zones along the Jordan basin and into the Red Sea occasionally cause earthquakes in the area.
The land formations can be divided into three main regions: in the west the Jordan Lowlands and the western heights, which extend throughout the country’s longitudinal north-south direction; to the east of these is the eastern plateau, which is the northwest extension of the land formations further south; and east of the Arabian Peninsula, without any natural barriers to neighboring Syria, Iraq and Saudi Arabia.
The land subsidence is part of the African-Syrian Rift Valley, with the water surface of the Dead Sea being the lowest point on the earth’s surface. Significant loads cover the valley floor and the lower portions. Artificial irrigation has made the Jordandalen the country’s most productive agricultural area.
The western heights consist of a hilly, partly torn landscape; in the north with the character of smaller plateaus and hills, and then to assume mountain range formations further south. The entire stretch is cut up by east-west valleys that flow into the Jordan River, most only with water flow during the winter months. The altitudes are lowest to the north, 400–1000 meters above sea level, while the southern part rises considerably higher. Jordan’s highest mountain, Jebel um Adaami (1823 meters above sea level), lies just east of Aqaba. The heights north of Wadi Hasa consist mainly of limestone with basalt parts. These areas are by nature the most fertile in Jordan and the majority of the country’s population lives here. Further south, sandstones gradually become more dominant.
Basalt showing cracking in hexagonal columns, near Eyjafjallajökull, southern Iceland.
Most of the eastern plateau is semi-desert or desert, comprising a northern area towards Syria, a wide valley area, Wadi Sirhan, which extends from the regions northeast of Zarqa to southeast into Saudi Arabia, and the southeastern desert areas. The height above the sea varies between 700-1000 meters, only the valley area is considerably lower. The entire plateau is sparsely populated, especially the desert in the south.