BackgroundThe Harrat Ithnayn volcanic field started to erupt about 3 million years ago and overlies Cambrian sandstones and Precambrian basement rocks. The volcanic vents are roughly aligned in N-S direction, but are more scattered than those of the other Harrats in the area.
The magmas of Harrat Ithnayn are of basaltic and basanitic composition and lack the silicic components present in neighboring Harrat Khaybar.
Ithnayn is one of 3 coalesced basaltic lava fields, Harrats Khaybar, Ithnayn, and Kura, which constitute the largest contiguous area of Cenozoic basalt in Saudi Arabia, similar in extent (20,564 km2) and volume (1,850 km3) to Harrat Rahat, which is situated only 25 km to the south (from: Camp et al, 1991)
Many lava caves are found across Arabia's basalt fields. One of the most known of the Harrat Ithnayn field is the 530 m long Kahf Al Shuwamis Lava Tube (Shuwaymis Cave, Shisma Cave), located at the base of Hazim Al Khadra volcano 240 km north-northeast of Medina. Thermal activity, manifested in fumaroles emanating from shelter caves are nearby.
- Smithsonian / GVP volcano information
- Camp V E, Roobol M J, Hooper P R (1991) "The Arabia continental alkali basalt province: Part II. Evolution of Harrats Khaybar, Ithnayn, and Kura, Kingdom of Saudi Arabia", Geol Soc Amer Bull, v 103, pp 363-391
- Saudi Cave Unit "MAPS OF CAVES SURVEYED BY SAUDI GEOLOGICAL SURVEY, KINGDOM OF SAUDI ARABIA", SGS, KSA, 2007
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