Hundreds of millions of years ago, the Negevdesert was covered by an ocean. Slowly, this started to recede northwards leaving behind a hump-shaped hill. The hump was slowly flattened by water and climatic forces. Approximately five million years ago, the Arava Rift Valley was formed, with rivers changing their courses, carving out the inside of the crater which was a softer rock than that overlying. The crater bottom continued to deepen at a much faster rate than the surrounding walls, which gradually increased in height. As the crater deepened, more layers of ancient rock were exposed with rocks at the bottom of the crater being up to 200 million years old. Today, the crater is 500 metres deep with the deepest point being Ein Saharonim which also contains the makhtesh's only natural water source, which sustains much of the wildlife in the makhtesh including onagers and ibex.
Geology
Makhtesh Ramon contains a diversity of rocks including clay hills known for their fantastic red and yellow colors and forms. Impressive mountains rise at the borders of the crater - Har Ramon at the southern end, Har Ardon at the north-eastern end, and two table mountains - Har Marpek, and Har Katum along the southern wall. The hills to the north-eastern edge of the makhtesh were once entirely covered by spiral ammonite fossils, ranging from the size of snails to that of tractor wheels although these have mainly been extracted so only smaller fossils can be found here today. Giv'at Ga'ash, a black hill in the north of the makhtesh was once an active volcano which erupted thousands of years ago and caused it to be covered in lava which quickly cooled in the open air, converting it into basalt. Limestone covered by basalt can also be found in smaller black hills in the southern part of the makhtesh, including Karnei Ramon. Shen Ramon is a rock made of magma which hardened whilst underground. It later rose up through cracks in the Earth's surface, and today stands in striking contrast with the nearby creamy coloured southern wall of the crater, as a black sharp-edged rock. In the centre of the makhtesh is HaMinsara, a low hill made up of columnar jointed sandstone - polygonal prismatic columns of quartzite. The pterioid bivalve Family Ramonalinidae is found in early Middle Triassic rocks of Makhtesh Ramon and was named after this feature. Nahal Ardon in the east of the makhtesh contains several vertical dikes. Occasional geodes of celestine can be found next to some of them.
Fauna
The Asian wild ass has been reintroduced to Makhtesh Ramon. In 1995 the population had increased to 40 adults in the area. The animals are hybrids of two different subspecies of the Asian Wild Ass. It is derived from the Turkmenian kulan and the Persian onager. The original subspecies, the Syrian wild ass, is completely extinct. Other larger mammals of the area include Nubian ibexes, Dorcas gazelles, striped hyenas and few Arabian leopards.
