Rocks...Freeze Thaw...?

Question

Would you find rocks that have been weathered due to a freeze thaw action in a desert? Explain.

Answer 1

Deserts occur in arctic areas as well as the sub-arctic. Temperature ranges of some deserts do reach the freezing point of water. Think about the location of the Gobi Desert, you can't tell me that it does not reach the freezing point during the winter months.

The weathering is cause by the expansion of water when it freezes into ice.

Answer 2

Yes, you would find rocks that have been weathered due to a freeze thaw action in a desert.

The reason for this is that during the day, temperatures are very high in the desert, but at night they fall to very low values. Rocks therefore respond to this situation by expanding (due to freezing at night) and contracting (due to thawing by day). Over time, they start scalling off and may form screes at the base of the parent rock.

Answer 3

Sure. Freezing and thawing happens in deserts. The freezing cracks rocks that are wet. Deserts can also have plenty of water. Especially during flash floods or when a river flows through a desert. Some deserts have lakes. Deserts just don't have much precipitation.

Answer 4

Yes you would.

Mechanical Weathering
Freezing water

Rainwater will collect in cracks in rock. If this water freezes, it expands as it forms ice and pushes on the inside of the crack, making the crack wider and helping to break the rock apart.

Hot / cold cycles

When a rock is heated up it expands. When it cools down it contracts (gets smaller). Repeated heating and cooling weakens the rock and eventually breaks it apart. (This is a slower version of what happens if you put a very hot glass object into very cold water - it cracks). This type of weathering is very important in hot deserts, where it is very hot in the day time but cold at night.

Insolation Weathering

Insolation weathering occurs in deserts where rocks and minerals break up because of the large fluctuations of temperature. Because rocks are poor conductors of heat, their surfaces heat up and expand more than the interiors, and a steep temperature gradient is established. This leads to stresses being set up, which in turn cause fracturing. This process is most effective in the presence of small amounts of moisture. The outer layers of the rock fracture and peel, or exfoliate, from the parent rock, a process sometimes referred to as “onion-skin” weathering because of the resulting rock’s appearance. In some rock types differential heating and expansion of the individual grains or crystals, particularly in coarse igneous rocks such as granite, can lead to the so-called granular disintegration, as the crystals or grains break away from the parent rock.