COURSE LECTURE NOTES:
SCIENCE | MATTER |
SOLAR SYSTEM |
PLANETS | ATMOSPHERE |
WIND and TEMPERATURE |
HUMIDITY | WEATHERING |
SEASONS | MASS WASTING |
SEASONS and CLIMATE |
WIND WORK |
STREAMS | LAND FORMS |
GROUND WATER |
CAVES/KARST | THE OCEAN |
TIDES & ESTUARIES |
WAVES | GLACIERS |
GLACIAL LANDFORMS |
VOLCANOES | VOLCANOES |
CHON | PLATE TECHTONICS |
CLIMATE CHANGE |
Geological Work Performed by Wind
Wind work is most powerful in the desert. There is very little water, so most of the erosion, transportation, and deposition is done by the wind.
1. Wind erosion
a. Direct abrasion - sand blasting, scraping. Wind speeds in the desert can reach 161 km/hr, which can easily sandblast the paint off an automobile. The same applies to rock. Over time, milimeter by milimeter sand grains are broken off and the rock worn away. The new sand contribute to the erosion. Wind + sand = more sand.
b. Direct lifting - the wind lifts the erode particles from where they had rested.
2. Wind transportation - similar to a stream
a. Bed load - some contact with the ground. Saltation - bouncing along. The heavier material rolls along.
b. Suspended load - dust, big dust clouds i.e. dust clouds in Santa Ana Winds. Dust can go a long way,even across oceans, i.e. Africa to the West Indies.
c. Dissolved load - very fine grained stuff i,e, decomposed plant matter (pine scent), sea salts, man-made pollutants.
Land forms shaped by wind
1. Erosional forms
a. blowout - hole in the sand from wind blowing onto one area, saucer shaped depression
b. zengen - bottom blown off by wind - mushroom shaped
c. yardong - ridge of rock sticking up that has been exposed by wind
2. Deposition forms
a. loess - very fine dust deposited from suspended load. May be several hundred feet deep. Can be very dangerous in earthquakes or with large water supply. People have dug out homes in loess deposits.
b. sand dunes - deposit of sand
1) free (migrating)dunes - these migrate, distance varies.
2) anchored dunes - held in position by vegetation or other obstacle.
a) nebkla - mound caused by plant trapping sand
Desert Pavement- surface of very old rocks that don't move, they are stuck in the surounding material. The large rocks move up by wet/dry cycles. They protect the moisture below them and the dry ground sinks. If formed this way, there will be loess below the rock. If formed by the traditional way, sheet wash removes finer material and leaves rock, there will be no loess below.