makhtesh

Makthesh Ramon
© DigitalGlobe

One of the two makhteshim in Sinai
© DigitalGlobe

A makhtesh (Hebrew: מכתש‎, plural: מכתשים - "makhteshim") is a geological phenomenon in which a hard outer layer of rock covers softer rocks. The erosion process destroys the soft minerals relatively fast, and they are washed away from under the harder ones. The harder rocks eventually collapse under their own weight — the result is a crater-like valley structure.

This phenomenon is often said to be unique to the Negev desert (Israel) and the Sinai Peninsula (Egypt). However, very similar features exist also in Turkmenistan (Yor-oilan-duz depression in Badkhyz Highlands) and Iran.

Although the word "makhtesh" is usually translated from Hebrew as "a crater", it isn't totally correct: makhteshim have been formed by water erosion and not by a meteorite strike (like impact craters) or a volcano eruption. They can also be called erosion craters, following the German name.

In the Negev, there are 5 makhteshim: Makhtesh Ramon, Makhtesh Gadol ("The Large Makhtesh"), Makhtesh Qatan ("The Small Makhtesh"), and two tiny makhteshim on Mount Arif.

In the cases in the Negev and Sinai, the hard rocks are limestone and dolomites, while the inner softer rocks are chalks and, in the major cases sandstone[1].

Though in most cases a makhtesh has only one drainage system, Makhtesh Ramon has three.

The two makhteshim in Sinai have no names for the basin, but the their walls have several names - like Jabal al-Manzur or Gebel Maghara.

Acacia tree inside Makhtesh Gadol, Israel; June 2007.	Center of Makhtesh Gadol, Israel; June 2007.	Mist flowing over the northern rim of Makhtesh Gadol, Israel; June 2007.	Road on northern side of Maktesh Gadol, Israel; originally built by the British during oil exploration; June 2007.
Ramon Fault on the southern side of Makhtesh Ramon, Israel; June 2007.	Ramon Fault on the southern side of Makhtesh Ramon, Israel; June 2003.

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