Ramon Crater

The Ramon Crater Nature Reserve protects the Makhtesh Ramon, in the Negev desert, some 85 kilometres south of Beersheba, in southern Israel. The depression is about 40 kilometres long, between 2 and 10 wide and some 500 metres deep, and is the largest erosion cirque in the world.

Its name is misleading: it is not a crater. It was formed neither by a meteorite nor by an eruption. A makhtesh is a landform found only in the Israeli Negev and the Egyptian Sinai, and its origin is purely erosional. Millions of years ago the area was covered by the Tethys Sea; when it withdrew, an upwarp was left in which hard layers of dolomite and limestone covered softer ones of sandstone and chalk. Tectonic uplift fractured the hard cover, water penetrated and emptied the soft interior, and finally the roof collapsed, leaving a closed, flat-floored valley ringed by vertical walls. The seasonal channels of the Ramon and the Ardon are still cutting into it.

The floor exposes a geological sequence of great teaching value, with multicoloured sandstones, volcanic rock, igneous dykes and fossils, and formations such as the Carpenter, an outcrop of sandstone prisms. The extreme aridity — some twenty-five millimetres of rain a year — leaves the geology completely exposed, which is why the site is used as a calibration area for airborne and satellite hyperspectral sensors. It is also an International Dark Sky Park, the first recognised in the Middle East.