Socotra is one of the most isolated landforms on Earth of continental origin (i.e. not of volcanic origin).The archipelago was once part of the supercontinet of Gondwana and detached during the Miocene, in the same set of rifting events that opened the Gulf of Aden to its northwest. The archipelago consists of the main island of Socotra (3,665 km2) and the three smaller islands of Abd al Kuri, Samhah and Darsa and small rock outcrops like Ka’l Fir’awn and Sābūnīyah that are uninhabitable by humans but important for seabirds.
The main island has three geographical terrains: the narrow coastal plains, a limestone plateau permeated with karstic caves, and the mountains. rising. The dominant landscape feature of Socotra island is the extensive plateau of Cretaceous limestone averaging 300 to 700 m in elevation. The plateau rises near the Haghier mountains in the northwest (maximum elevation 1,519 m), which are composed of Precambrian granites and metamorphic rocks. The plateau then declines abruptly at the extreme western portion of the island, falling in steep escarpments to the coastal plainsor directly into the ocean.
The coastal plains can reach up to 5 km in width and are found around most of the island. They consist mainly of alluvial soils of stone and coarse sand. Sand dunes can occur in some areas, particularly in the Noged Plain, a 60 km stretch of unbroken plain in the south.
Dana Pietsch and Miranda Morris, 2010. Modern and Ancient Knowledge of Conserving Soils in Socotra Island, Yemen. Vol9, pp 375-386. P. Zdruli et al. (eds.), Land Degradation and Desertification: Assesment, Mitigation and Remediation, DOI 10.1007/978-90-481-8657-0_29, Springer Science+Business Media B.V. 2010