Bolson

A bolson is a desert valley or depression that usually drains into a playa or salt pan and is entirely enclosed by recently uplifted hills or mountains, forming a closed, endorheic drainage basin typical of basin-and-range topography. The surrounding uplifted terrain traps water and sediment inside the valley rather than letting it drain to the sea, so sediment steadily accumulates on the basin floor. The word entered American English in the 1830s and 1840s during exploration of western North America, borrowed from the Spanish bolson, meaning large purse, and the Hueco Bolson in Texas and the Mesilla Bolson spanning southern New Mexico and northeastern Chihuahua are commonly cited examples.