The Umm al Samim (also known as the Umm as Samim) is a quicksand

Quicksand

Quicksand is a colloid hydrogel consisting of fine granular matter , clay, and water.Water circulation underground can focus in an area with the optimal mixture of fine sands and other materials such as clay. The water moves up and then down slowly in a convection-like manner throughout a column...

 area on the eastern edge of the Rub al'khali desert

Desert

A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...

 within Oman

Oman

Oman , officially called the Sultanate of Oman , is an Arab state in southwest Asia on the southeast coast of the Arabian Peninsula. It is bordered by the United Arab Emirates to the northwest, Saudi Arabia to the west, and Yemen to the southwest. The coast is formed by the Arabian Sea on the...

's borders. The waters, such as they are, drain into this brackish low-lying closed basin area off the Omani mountains and the wadi

Wadi

Wadi is the Arabic term traditionally referring to a valley. In some cases, it may refer to a dry riverbed that contains water only during times of heavy rain or simply an intermittent stream.-Variant names:...

s of the Rub al'khali. The Al Samim (known locally as the 'Mother of Poisons' or the 'Mother of Worries') is a salt marsh with a solid-looking crust but can be very treacherous when broken through. There is little vegetation.

Sir Wilfred Thesiger

Wilfred Thesiger

Sir Wilfred Patrick Thesiger, CBE, DSO, FRAS, FRGS was a British explorer and travel writer born in Addis Ababa, the capital of Ethiopia.-Family:...

, the traveller and explorer, was the first European to see the area in the late 1940s after his travels from Salalah in Oman.