The Eastern Desert (known archaically as Arabia or the Arabian Desert) is the part of the Sahara desert that is located east of the Nile river. It spans of northeastern Africa and is bordered by the Nile river to the west and the Red Sea and Gulf of Suez to the east. It extends through Egypt, Eritrea, Sudan and Ethiopia. The Eastern Desert is also known as the Red Sea Hills. The Eastern Desert consists of a mountain range which runs parallel to the coast, wide sedimentary plateaus extending from either side of the mountains and the Red Sea coast. The rainfall, climate, vegetation and animal life sustained in the desert varies between these different regions. The Eastern Desert has been a mining site for building materials, as well as precious and semi-precious metals, throughout history. It has historically contained many trade routes leading to and from the Red Sea, including the Suez Canal.
Geography
Historical formation
Between 100 and 35 million years ago the area that is now the Eastern Desert was underwater, covered by the Tethys Ocean. During the Oligocene period, around 34 million years ago, the land began to tilt and the coastline was pushed back to the north and west. Concurrently, the basement complex to the east was uplifted, forming the mountain range of the Desert. In this same sequence of land movements, a rift which is now the Red Sea was opened up.
Mountains
The mountain range of the Eastern Desert runs between inland from and parallel to the Red Sea Coast. It has peaks around above sea level. The southern mountains are predominantly composed of igneous rock while the mountains to the north are composed of limestone. Separating the mountains are wide wadis which allow for the runoff of rainfall from the mountains to the Red Sea and the Nile River. The mountain range's highest peak is Gebel Shayeb EI-Banat at above sea level. Other significant peaks include Jebel Erba () Jabal Oda (), Jabal Shaib al Banat (), Jebel Hamata (), Gebel Amm Anad (), South Galala (), and North Galala ().
Plateaus
Sedimentary plateaus run on either side of the mountains. In general, the northern sections of these plateaus have a limestone base while the southern sections are sandstone. The plateau between the Nile River and the mountains is also known as the inland Eastern Desert and is subdivided into four sections: The Cairo-Suez Desert, The Limestone Desert, The Sandstone (Idfu-Kom Ombo) Desert, and the Nubian Desert.
Red Sea coast
The Red Sea coastland is the easternmost part of the Eastern Desert, running between Eritrea and the Gulf of Suez. The distance between the coastline and the base of the mountain range varies between .
Climate
The Eastern Desert has a semi-arid/arid/hyper-arid climate. On average, the region usually receives less than of rainfall per year in infrequent patterns. Most of the rainfall occurs during the winter months around the mountains. The presence of the mountains can create a rain shadow for the rest of the Desert, contributing to the arid environment.
Average temperatures are between in winter (November–March) and in summer (May–September). The weather is typically sunny; however, sandstorms can occur, usually between March and June. The storms (khamsins) are caused by tropical air moving up from Sudan, accompanied by strong winds and higher temperatures. The term khamsin comes from the Arabic word meaning fifty, as the storms occur on an average of fifty days per year.
Historic climate
Carbon dating of samples of fossil tufas, a type of limestone which is deposited in the presence of high groundwater levels, has revealed that there have historically been two periods when the Eastern Desert was significantly wetter than it is today. These occurred in the late Pleistocene age, around 100,000 years ago, and the mid Holocene age, around 6,000 years ago. The most recent wet period is known to have been a result of summer monsoonal rains that moved over the Desert from the Indian Ocean. During these times, some areas of the land were swamp. The mountains and desert plateaus were also able to sustain more vegetation and animals. In between these periods the desert climate has remained mostly arid, as it is today.
Flora
The vegetation growing in the Eastern Desert is classified as either ephemeral or perennial. Ephemeral vegetation are plants which usually have a single season lifespan due to their dependence on rain. Perennial plants live for two or more years.