Mirages are particularly prevalent in deserts. They occur when light travels between two layers of air with varying temperatures. The desert sun warms the sand, which heats the air directly above it. The heated air reflects the sky and bends light beams. This creates a mirage: an image of distant objects such as mountains or water that appears in the sky.
This phenomenon has been used for thousands of years by travelers to provide them with an illusion of safety while they were far from home. Modern-day travelers can enjoy this same advantage by visiting hot springs or other remote places where there is usually no danger of running into people.
Deserts contain lots of small particles that reflect heat back up into the atmosphere. Because clouds form in warm regions, deserts tend to have more clear days than non-desert areas. Clouds block out some sunlight and cause it to rain somewhere else. Raindrops evaporate fast so most deserts remain dry except during occasional wet periods.
Many scientists think that climate changes caused by things like increased CO2 production can lead to more frequent droughts and floods. Climate models predict that if CO2 levels keep rising, there will be more intense drought and flood events every year. Scientists think that this may be why we're seeing more frequent and severe storms all over the world right now...including in Phoenix!
Weathering processes cause deserts to emerge when substantial temperature differences between day and night impose strain on the rocks, causing them to shatter into fragments. The wind smoothes down the rocks and arranges the sand into homogeneous deposits. The granules eventually become flat sheets of sand or pile up in billowing sand dunes.
Weathering also occurs at a slower rate where there are no strong winds to blow away debris that would otherwise cover the surface of the land. In this case, new material is added to the surface from below, forming layers of rock that become weathered over time.
Deserts form either when snow melts at lower altitudes during hot summers or when rain falls at higher elevations then runs down steep slopes without being absorbed into the soil. Deserts can also appear after glaciers melt at the end of an ice age. The most extensive desert in the world is the Sahara, which covers roughly one-fifth of Africa. Other major deserts include the Sonoran, Mojave, and Great Basin deserts in North America; the Gobi and Takla Makan deserts in Asia; and the Kalahari, Sahel, and Chihuahuan deserts in Africa.
The term "desert" is used to describe any area of dryness and barrenness caused by lack of precipitation. Deserts can be divided up into two general categories: hyperdeserts and arid deserts.
This set contains the following terms: (67) The white sand on a beach appears to sparkle with light on a sunny day. What technique explains why the sand is so brilliantly colored? Indicates that a high temperature causes visible light to be emitted. Abrasive particles in the sand cause sunlight to break down into colors like red, orange, yellow, green, blue, and violet when it passes through them.
The brilliant color of the sand on a beach results from the presence of mineral grains in the sand that reflect light of different colors. For example, red sands are common in areas where there is much iron in the soil, while yellow sands often occur where there is lots of clay available for grinding up under foot traffic. White sands are also very common and are found near the ocean where there is a constant flow of water and wind that wears away at the rocks and shells below sea level.
Mineral-rich soils tend to be more colorful than those without many minerals because they have more opportunities to break down light waves as they pass through them. The sun's heat can also play a role by causing certain minerals to glow when they encounter ultraviolet light waves. For example, zeolites (minerals used as catalysts for chemical reactions) come in various colors such as black, brown, gray, green, pink, red, and white.