The Mediterranean coast and the
Sahara Desert are the country's most prominent natural features. There are several highlands but no true mountain ranges except in the largely empty southern desert near the Chadian border, where the
Tibesti Massif rises to over 2,200 metres. A relatively narrow coastal strip and highland steppes immediately south of it are the most productive agricultural regions. Still farther south a pastoral zone of sparse grassland gives way to the vast
Sahara Desert, a barren wasteland of rocky plateaus and sand. It supports minimal human habitation, and
agriculture is possible only in a few scattered
oases. The Sahara desert is connected to the
Gulf of Sidra on the coast by a barren zone, known as the Sirtica, which has great historical significance. Along the shore of
Tripolitania for more than 300 km, coastal oases alternate with sandy areas and lagoons. Inland from these lies the Jifarah Plain, a triangular area of some 15,000 square km. About 120 km inland the plain terminates in an escarpment that rises to form the
Nafusa Mountains, with elevations of up to 1,000 metres, which is the northern edge of the Tripolitanian Plateau. In the eastern part of the country,
Cyrenaica, there are fewer coastal oases. Cyrenaica's Marj Plain covers a much smaller area than the corresponding Jifarah Plain of Tripolitania. The lowlands form a crescent about 210 km long between
Benghazi and
Derna and extend inland a maximum of 50 km. Elsewhere along the Cyrenaican coast, the precipice of an arid plateau reaches to the sea. Behind the Marj Plain, the terrain rises abruptly to form
Jabal al Akhdar (Green Mountain), so called because of its leafy cover of
pine,
juniper,
cypress, and wild
olive. It is a
limestone plateau with maximum altitudes of about 900 metres. From Jabal al Akhdar, Cyrenaica extends southward across a barren grazing belt that gives way to the Sahara Desert, which extends still farther southwest across the Chadian frontier. Unlike Cyrenaica, Tripolitania does not extend southward into the desert. The southwestern desert region, known as
Fezzan, was administered separately during both the Italian regime and the federal period of the Libyan monarchy. The large dune seas known as
ergs of the
Idehan Ubari and the
Idehan Murzuq cover much of the land of Fezzan. The
Haruj volcanic field is in the northeast part of Fezzan. In 1969 the revolutionary government officially changed the regional designation of Tripolitania to Western Libya, of Cyrenaica to Eastern Libya, and of Fezzan to Southern Libya; however, the old names were intimately associated with the history of the area, and during the 1970s they continued to be used frequently. Cyrenaica comprises 51%, Fezzan 33%, and Tripolitania 16% of the country's area. Before Libya achieved independence, its name was seldom used other than as a somewhat imprecise geographical expression. The people preferred to be referred to as natives of one of the three constituent regions. The separateness of the regions is much more than simply geographical and political, for they have evolved largely as different socioeconomic entities – each with a culture, social structure, and values different from the others. Cyrenaica became Arabized at a somewhat earlier date than Tripolitania, and Beduin tribes dominated it. The residual strain of the indigenous Berber inhabitants, however, still remains in Tripolitania. Fezzan has remained a kind of North African outback, its oases peopled largely by minority ethnic groups. The border between Tripolitania and Tunisia is subject to countless crossings by legal and illegal migrants. No natural frontier marks the border, and the ethnic composition, language, value systems, and traditions of the two peoples are nearly identical. The Cyrenaica region is contiguous with Egypt, and here, too, the border is not naturally defined; illegal as well as legal crossings are frequent. In contrast, Fezzan's borders with Algeria, Niger, and Chad are seldom crossed because of the almost total emptiness of the desert countryside. Other factors, too, such as the traditional forms of land tenure, have varied in the different regions. In the 1980s their degrees of separation were still sufficiently pronounced to represent a significant obstacle to efforts toward achieving a fully unified Libya. ==Area and boundaries==