Persian Gulf flooding of the basin started 15,000 years ago due to rising sea levels of the Holocene glacial retreat. This inland sea of some is connected to the Gulf of Oman in the east by the Strait of Hormuz; and its western end is marked by the major river delta of the Shatt al-Arab, which carries the waters of the Euphrates and the Tigris. In Iran this is called "Arvand Rood", where "Rood" means "river". Its length is , with Iran covering most of the northern coast and Saudi Arabia most of the southern coast. The Persian Gulf is about wide
Gulf of Oman desert and semi-desert gravelly plains and savanna with thorny acacia trees inland with a background of the Musandam and Al Hajar mountains. The climate is hot and dry with temperatures up to 49 degrees Celsius (120 °F) and little rainfall, especially on the Persian Gulf coast of the UAE. There is more rainfall on the Gulf of Oman and humidity provides moisture on both coasts. The coastal mangrove consists of "Avicennia marina", trees of the inland savanna include "Ziziphus spina-christi", "Prosopis cineraria" and the Umbrella Thorn "Acacia tortilis" while the mountains are home to "Ficus cordata salicifolia", and "Acacia tortilis". Finally the traditional