The studies of different desert pavements have yielded different age estimates ranging from thousands to tens of thousands of years. However, all the theories incorporate the role of wind, erosion, and rains in the formation process.
A common theory suggests that desert pavements are formed through gradual removal of sand and other fine particles by the wind and intermittent rains leaving behind the large fragments. The larger rock particles are shaken into place by actions of different agents such as rain, wind, gravity, and animals.
Once the pavement is formed the removal of fine particles ceases because the pavement acts as a barrier to further erosion. The second theory suggests that desert pavements are formed from a shrink or swell properties of clay under the pavement. The clay expands when it absorbs the water and cracks along weak planes when it dries.
The rock fragments are large enough not to slip back down into the cracks while the fine particles can fill the cracks. With time, the pavement stabilizes preventing further changes to its formation. The third theory is used to explain the formation of desert pavement in Cima Volcanic Field. Here, the top layer is the beginning point whereby it is deposited and begins to undergo weathering by the wind.
The rocks on the surface are fractured due to hot climate change. The silt infiltrates the spaces between the fragments reaching below the top layer causing the layer to be pushed upwards. Wells used a method based on cosmogenic helium-3, which forms by cosmic ray bombardment at the ground surface. Helium-3 is retained inside grains of olivine and pyroxene in the lava flows, building up with exposure time. The helium-3 dates show that the lava stones in the desert pavement at Cima Dome have all been at the surface the same amount of time as the solid lava flows right next to them.
It's inescapable that in some places, as he put it in a July article in Geology , "stone pavements are born at the surface. For the geologist, this discovery means that some desert pavements preserve a long history of dust deposition beneath them. The dust is a record of ancient climate, just as it is on the deep sea floor and in the world's ice caps. To those well-read volumes of Earth history, we may be able to add a new geologic book whose pages are desert dust.
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Measure content performance. Develop and improve products. List of Partners vendors. Share Flipboard Email. Andrew Alden. Geology Expert. Research shows that bees, hornets and wasps have caused the most deaths in Arizona, year-on-year, with many of these deaths caused by an allergic reaction.
Aside from the oppressive heat and lack of water, the desert is also full of critters that can bite and sting. Spiders, scorpions, centipedes, and snakes are all found in dark places — caves, abandoned buildings and under rocks. Desert Dangers. There are some hazards unique to desert survival. These include insects like scorpions , snakes, thorned plants and cacti, contaminated water, sunburn, eye irritation and climatic stress.
Global warming is increasing the incidence of drought, which dries up water holes. Higher temperatures may produce an increasing number of wildfires that alter desert landscapes by eliminating slow-growing trees and shrubs and replacing them with fast-growing grasses. Human exploitation of fragile ecosystems can lead to the droughts and arid conditions characteristic of desertification. Effects include land degradation, soil erosion and sterility, and a loss of biodiversity, with huge economic costs for nations where deserts are growing.
The great desert was born some 7 million years ago, as remnants of a vast sea called Tethys closed up.
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