Environmental and Economic Costs of Soil Erosion and Conservation Benefits
David Pimentel, C. Harvey, P. Resosudarmo, K. Sinclair, D. Kurz, M. McNair, S. Crist, L. Shpritz, L. Fitton, R. Saffouri, and R. BlairScience 24 February 1995 267: 1117-1123 [DOI: 10.1126/science.267.5201.1117] (in Articles)
The Impact of Agricultural Soil Erosion on the Global Carbon Cycle
K. Van Oost, T. A. Quine, G. Govers, S. De Gryze, J. Six, J. W. Harden, J. C. Ritchie, G. W. McCarty, G. Heckrath, C. Kosmas, J. V. Giraldez, J. R. Marques da Silva, and R. MerckxScience 26 October 2007 318: 626-629 [DOI: 10.1126/science.1145724] (in Reports)
Accumulation and Erosion of Mars' South Polar Layered Deposits
Roberto Seu, Roger J. Phillips, Giovanni Alberti, Daniela Biccari, Francesco BonaventuraScience 21 September 2007 317: 1715-1718 [DOI: 10.1126/science.1144120] (in Reports)
Deep-Sea Erosion and Manganese Nodule Development in the Southeast Indian Ocean
J. P. Kennett and N. D. WatkinsScience 6 June 1975 188: 1011-1013 [DOI: 10.1126/science.188.4192.1011] (in Articles)
Submarine Canyon Erosion: Contribution of Marine Rock Burrowers
John E. Warme, Thomas B. Scanland, and Neil F. MarshallScience 17 September 1971 173: 1127-1129 [DOI: 10.1126/science.173.4002.1127] (in Articles)
Monday, May 19, 2008
Saturday, May 17, 2008
Original Idea........
What if the Dust Bowl had never ended?
We would be in terrible situation where we would have little or no crops. Therefore as a result we would have no food so people would start to die. In the US we have many crops that would stop permanently because lack of water and sunlight. The photosynthesis process would be destroyed. Many countries depend on world for some crops that they do not grow.
We would have a harder time to make any construction because we would have to use material in order to cover our eyes. Also many people would get blind and cause many problems.
People's repiratory systems would be infected due to virus and bacteria that flows in the sandstorm daily. Each day people would get infected and miollions would die.
Virus would spread very fast where it would spread around the world leading to a permanent stop in society.
We would be in terrible situation where we would have little or no crops. Therefore as a result we would have no food so people would start to die. In the US we have many crops that would stop permanently because lack of water and sunlight. The photosynthesis process would be destroyed. Many countries depend on world for some crops that they do not grow.
We would have a harder time to make any construction because we would have to use material in order to cover our eyes. Also many people would get blind and cause many problems.
People's repiratory systems would be infected due to virus and bacteria that flows in the sandstorm daily. Each day people would get infected and miollions would die.
Virus would spread very fast where it would spread around the world leading to a permanent stop in society.
Tuesday, May 13, 2008
Dust Bowl Pics
America's worst erosion was the Dust Bowl. Here are pics below
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The Dust Bowl, or the "dirty thirties", was a period of horrible dust storms causing major ecological and agricultural damage to American and Canadian prairie lands from 1930 to 1936 (in some areas until 1940), caused by severe drought coupled with decades of extensive farming without crop rotation or other techniques to prevent erosion. It was a mostly man-made disaster caused when virgin top soil of the Great Plains was exposed to deep plowing, killing the natural grasses - the grasses normally kept the soil in place and moisture trapped, even during periods of drought and high winds. However, during the drought of the 1930s, with the grasses destroyed, the soil dried, turned to dust, and blew away eastwards and southwards in large dark clouds. At times the clouds blackened the sky, reaching all the way to East Coast cities like New York and Washington D.C., with much of the soil deposited in the Atlantic Ocean. The Dust Bowl consisted of 100 million acres, centered on the panhandles of Texas, Oklahoma, New Mexico, Colorado, and Kansas.
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The Dust Bowl, or the "dirty thirties", was a period of horrible dust storms causing major ecological and agricultural damage to American and Canadian prairie lands from 1930 to 1936 (in some areas until 1940), caused by severe drought coupled with decades of extensive farming without crop rotation or other techniques to prevent erosion. It was a mostly man-made disaster caused when virgin top soil of the Great Plains was exposed to deep plowing, killing the natural grasses - the grasses normally kept the soil in place and moisture trapped, even during periods of drought and high winds. However, during the drought of the 1930s, with the grasses destroyed, the soil dried, turned to dust, and blew away eastwards and southwards in large dark clouds. At times the clouds blackened the sky, reaching all the way to East Coast cities like New York and Washington D.C., with much of the soil deposited in the Atlantic Ocean. The Dust Bowl consisted of 100 million acres, centered on the panhandles of Texas, Oklahoma, New Mexico, Colorado, and Kansas.
By 1940, 2.5 million people had moved out of the Plains states; of those, 200,000 moved to California.
Reference:"Wikipedia." 26 May 2008 .
Saturday, May 10, 2008
Erosion In Depth
What causes valleys to form? Why do streams and lakes get muddy after a rain storm? Why are the rocks at the bottom of a river usually round? The answer to all these questions is EROSION!
Erosion is the process by which the surface of the Earth gets worn down. Erosion can be caused by natural elements such as wind and glacial ice. But anyone who has ever seen a picture of the Grand Canyon knows that nothing beats the slow steady movement of water when it comes to changing the Earth.
The key to erosion is something called "fluid flow." Water, air, and even ice are fluids because they tend to flow from one place to another due to the force of gravity. Of the three, liquid water is the most common agent of erosion because there's so much of it on the surface of the Earth.
The key to erosion is something called "fluid flow." Water, air, and even ice are fluids because they tend to flow from one place to another due to the force of gravity. Of the three, liquid water is the most common agent of erosion because there's so much of it on the surface of the Earth.
Erosion is the process that breaks things down. As far as we're concerned, erosion is the breakdown of the continents and the land around you. The overall effect of breaking down and weathering the land is called denudation. Denudation is the process of erosion. In nature, large things are broken down into smaller things. Boulders become sand. Mountains are rained on and become hills. The pieces of the mountain become smaller pieces and go down the sides of hills. Weathering and erosion always happen in a downhill direction. Erosion is an easy idea to understand. If you see a rock, pull it out of a mountain. Then throw it down on the ground. You are now a part of the erosion of that mountain. You have taken a big object (a mountain) and started to make little objects out of it (a rock). When that rock hit the ground, it could have cracked and made some tiny pieces of rock (sand). Erosion is just that easy. When it rains, the same process happens. Rocks are washed down a mountain or down a stream. Soils are washed away. The ocean beats against a cliff and breaks it apart. They are all examples of denudation.
Things don't just disappear. The masses of dirt and rock are moved to another form and place. Scientists call it mass wasting. The wasting is the loss of matter in one place. Mass wasting can happen two ways: 1) mechanical, similar to breaking a rock with a hammer; and 2) chemical, similar to pouring acid on a rock to dissolve it.
DOES EROSION BUILD THINGS UP?Erosion happens at the tops of mountains and under the soil. Water and chemicals get into the rocks and break them up through those mechanical and chemical forces. Erosion in one area can actually build up lower areas. Think about a mountain range and a river. As the mountain erodes, the river carries sediment downstream towards the ocean. That sediment slowly builds up and creates new wetlands at the mouth of the river. The swamps of Louisiana are good examples of sediment carried by the Mississippi River and collected at the
Reference:"Erosion." Geography 4 Kids. 26 May 2008 .
Transpiration
Water is removed from the surface of the Earth to the atmosphere by two distinct mechanisms: evaporation and transpiration.
Evaporation can be defined as the process where liquid water is transformed into a gaseous state. Evaporation can only occur when water is available. It also requires that the humidity of the atmosphere be less than the evaporating surface (at 100% relative humidity there is no more evaporation). The evaporation process requires large amounts of energy. For example, the evaporation of one gram of water requires 600 calories of heat energy.
Transpiration is the process of water loss from plants through stomata. Stomata are small openings found on the underside of leaves that are connected to vascular plant tissues. In most plants, transpiration is a passive process largely controlled by the humidity of the atmospheric and the moisture content of the soil. Of the transpired water passing through a plant only 1% is used in the growth process. Transpiration also transports nutrients from the soil into the roots and carries them to the various cells of the plant and is used to keep tissues from becoming overheated. Some dry environment plants do have the ability to open and close their stomata. This adaptation is necessary to limit the loss of water from plant tissues. Without this adaptation these plants would not be able to survive under conditions of severe drought.
It is often difficult to distinguish between evaporation and transpiration. So we use a composite term evapotranspiration. The rate of evapotranspiration at any instant from the Earth's surface is controlled by four factors:
Energy availability. The more energy available the greater the rate of evapotranspiration. It takes about 600 calories of heat energy to change 1 gram of liquid water into a gas.
The humidity gradient away from the surface. The rate and quantity of water vapor entering into the atmosphere both become higher in drier air.
The wind speed immediately above the surface. Many of us have observed that our gardens need more watering on windy days compared to calm days when temperatures are similar. This fact occurs because wind increases the potential for evapotranspiration. The process of evapotranspiration moves water vapor from ground or water surfaces to an adjacent shallow layer that is only a few centimeters thick. When this layer becomes saturated evapotranspiration stops. However, wind can remove this layer replacing it with drier air which increases the potential for evapotranspiration.
Water availability. Evapotranspiration cannot occur if water is not available.
On a global scale, most of the evapotranspiration of water on the Earth's surface occurs in the subtropical oceans (Figures 8i-1 and 8i-2). In these areas, high quantities of solar radiation provide the energy required to convert liquid water into a gas. Evapotranspiration generally exceeds precipitation on middle and high latitude landmass areas during the summer season. Once again, the greater availability of solar radiation during this time enhances the evapotranspiration process.
Evaporation can be defined as the process where liquid water is transformed into a gaseous state. Evaporation can only occur when water is available. It also requires that the humidity of the atmosphere be less than the evaporating surface (at 100% relative humidity there is no more evaporation). The evaporation process requires large amounts of energy. For example, the evaporation of one gram of water requires 600 calories of heat energy.
Transpiration is the process of water loss from plants through stomata. Stomata are small openings found on the underside of leaves that are connected to vascular plant tissues. In most plants, transpiration is a passive process largely controlled by the humidity of the atmospheric and the moisture content of the soil. Of the transpired water passing through a plant only 1% is used in the growth process. Transpiration also transports nutrients from the soil into the roots and carries them to the various cells of the plant and is used to keep tissues from becoming overheated. Some dry environment plants do have the ability to open and close their stomata. This adaptation is necessary to limit the loss of water from plant tissues. Without this adaptation these plants would not be able to survive under conditions of severe drought.
It is often difficult to distinguish between evaporation and transpiration. So we use a composite term evapotranspiration. The rate of evapotranspiration at any instant from the Earth's surface is controlled by four factors:
Energy availability. The more energy available the greater the rate of evapotranspiration. It takes about 600 calories of heat energy to change 1 gram of liquid water into a gas.
The humidity gradient away from the surface. The rate and quantity of water vapor entering into the atmosphere both become higher in drier air.
The wind speed immediately above the surface. Many of us have observed that our gardens need more watering on windy days compared to calm days when temperatures are similar. This fact occurs because wind increases the potential for evapotranspiration. The process of evapotranspiration moves water vapor from ground or water surfaces to an adjacent shallow layer that is only a few centimeters thick. When this layer becomes saturated evapotranspiration stops. However, wind can remove this layer replacing it with drier air which increases the potential for evapotranspiration.
Water availability. Evapotranspiration cannot occur if water is not available.
On a global scale, most of the evapotranspiration of water on the Earth's surface occurs in the subtropical oceans (Figures 8i-1 and 8i-2). In these areas, high quantities of solar radiation provide the energy required to convert liquid water into a gas. Evapotranspiration generally exceeds precipitation on middle and high latitude landmass areas during the summer season. Once again, the greater availability of solar radiation during this time enhances the evapotranspiration process.
Figure 8i-1: Precipitation minus evapotranspiration for an average January, 1959-1997(above)
Figure 8i-2: Precipitation minus evapotranspiration for an average July, 1959-1997
Know UR Facts
Thesaurus: evaporation
noun
The act or an example of passing out of sight: disappearance, evanescence, fade-out, vanishment.
Antonyms: evaporation
Definition: drying up; dissolutionAntonyms: dampening, soaking, wetting
Geography Dictionary: evaporation
The changing of a liquid into a vapour, or gas, at a temperature below the boiling point of that liquid.Evaporation occurs at the surface of a liquid, and energy is required to release the molecules from the liquid into the gas. The use of this energy, known as latent heat, causes the temperature of the liquid to fall.
Britannica Concise Encyclopedia: evaporation
Change of a liquid into the gaseous state; in particular, the process by which liquid water enters the atmosphere as water vapour. Evaporation, mostly from the sea and from vegetation, replenishes the humidity of the air. It is an important part of the exchange of energy in the Earth-atmosphere system that produces atmospheric motion, and therefore weather and climate. The rate of evaporation depends on the temperature difference between the evaporating surface and the air, the relative humidity, and wind.
For more information on evaporation, visit Britannica.com.
Sports Science and Medicine: evaporation
The conversion of liquid into vapour. Evaporation of sweat is the primary route for heat dissipation during exercise, accounting for up to 80% of heat lost from the body.
Columbia Encyclopedia: evaporation,
change of a liquid into vapor at any temperature below its boiling point. For example, water, when placed in a shallow open container exposed to air, gradually disappears, evaporating at a rate that depends on the amount of surface exposed, the humidity of the air, and the temperature. Evaporation occurs because among the molecules near the surface of the liquid there are always some with enough heat energy to overcome the cohesion of their neighbors and escape (see adhesion and cohesion; matter). At higher temperatures the number of energetic molecules is greater, and evaporation is more rapid. Evaporation is also increased by increasing the surface area of the liquid or by increasing the air circulation, thus carrying away the energetic molecules leaving the liquid before they can be slowed enough by collisions with air molecules to be reabsorbed into the liquid. If the air is humid some water molecules from the air will pass back into the liquid, thus reducing the rate of evaporation. An increase in atmospheric pressure also reduces evaporation. The process of evaporation is always accompanied by a cooling effect. For example, when a liquid evaporates from the skin, a cooling sensation results. The reason for this is that only the most energetic molecules of liquid are lost by evaporation, so that the average energy of the remaining molecules decreases; the surface temperature, which is a measure of this average energy, decreases also. Many refrigeration processes are based on this principle.
Science Dictionary: evaporation
The changing of a liquid into a gas, often under the influence of heat (as in the boiling of water). The evaporation of water from the oceans is a major component in the hydrologic cycle.
Up, Up in the Air = Evaporation
Warmth from the sun causes water from lakes, streams, ice, and soils to turn into water vapor in the air. Almost all of the precipitated water (80 percent) goes right back into the air because of evaporation. The rest runs off the land or soaks into the ground to become ground water.
The process by which a liquid is converted into a vapor. In the liquid phase, the substance is held together by intermolecular forces. As the temperature is raised, the molecules move more vigorously, and in increasingly high proportion have sufficient energy to escape from their neighbors. Evaporation is therefore slow at low temperatures but faster at higher temperatures. In an open vessel, the molecules escape from the vicinity of the liquid, and there is a net migration from the liquid to the atmosphere. In a closed vessel, net evaporation continues until the number of molecules in the vapor has risen to the stage at which the rate of return from the vapor to the liquid is equal to the rate of evaporation. At this stage there is a dynamic equilibrium between the liquid and its vapor, with evaporation and its reverse, condensation, occurring at the same rate. The pressure of the vapor in the closed vessel is called the vapor pressure of the substance; its value depends on the temperature. Boiling occurs in an open vessel (but not in a closed vessel) when the vapor pressure is equal to the ambient pressure. Evaporation is an endothermic (heat-absorbing) process because molecules must be supplied with energy to overcome the intermolecular forces. The enthalpy of vaporization, ΔvapH (formerly, the latent heat of vaporization) is the heat required at constant pressure per mole of substance for vaporization. The entropy of vaporization, ΔvapS, at the boiling point, Tb, is equal to ΔvapH/Tb. According to Trouton's rule, for many liquids the entropy of vaporization is close to 85 J/K · mol. This value reflects the similar change in disorder that occurs when a liquid is converted into a gas. However, certain liquids (water and mercury among them) are more structured than others, and have a bigger entropy of vaporization than Trouton's rule suggests.
Volatile liquids evaporate more rapidly than others at the same temperature. Such liquids have relatively weak intermolecular forces. In general, the rate of evaporation depends on the strengths of the intermolecular forces and the rate at which heat is supplied to the liquid.
Reference:"Evaporation." Answers.Com. 26 May 2008
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