Chapter 7.2 Deserts

Geologic Processes in Arid Climates Deserts usually have angular rocks, sheer canyon walls, and surfaces covered in pebbles or sand.

Weathering In deserts mechanical weathering occurs a lot to shape the land. Because there is not a lot of moisture or precipitation there is not a lot of chemical weathering. There is a little bit of chemical weathering that can happen.

The Role of Water Most desert streams will be dry and only carry water after it rains, these are called ephemeral streams. Usually these streams only last a few days or hours. These areas are also more susceptible to flash floods.

Basin and Range: A Desert Landscape Most of the time the streams formed in a desert area does not flow to lakes or the ocean. They are absorbed by the land. In a Basin and Range area there are small mountain ranges and when there are sporadic rains they move down the mountain and carry a lot of sediment but then settle at the bottom of the mountains and form an alluvial fan – a cone of debris.

In a Basin and Range area there are times a playa lake can form In a Basin and Range area there are times a playa lake can form. This is when there is a lot of rainfall or snowmelt and it goes into the center of the basin making a lake. These lakes only last a few days or weeks. When the water dries up the area is called a playa. Water still is responsible for most of the erosion that happens in deserts, wind is a very important factor of erosion in deserts also, but water is the most important.