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Grade 8 Quiz Review #2 – Water Systems Erosion - When precipitation falls, some flows over the land surface as runoff, which picks up particles of clay, sand and gravel Erosion is the wearing away and transport of the Earth’s materials. Water, wind, chemicals, and living things all cause erosion. Weathering breaks up the rock while erosion is the process in which carries away the rock Physical and Chemical Weathering – recognize examples and define o Chemical weathering occurs when water, air, and other materials react with rocks, changing the substances that make up rocks (new substance) o Mechanical weathering is a form of erosion caused by wind and water o Recognize examples of physical and chemical weathering Erosion by ice – moraines (Once a glacier starts to melt, it leaves the broken rocks it eroded in enormous piles) Weathering by plants Weathering: Fast or Slow Can occur quickly or slowly depending on a couple of factors o Size of rock o The mineral in the rock o Climate is important – cold winters mechanical weathering takes place What sedimentary rock is –includes gravel, sand, silt, and mud that is carried and deposited by wind, water, or ice What are some human activities that can increase erosion by decreasing the ability of the soil to retain water? Cutting trees Removing vegetation Land cultivation What are some effects of sediment-laden waters? Plants receive less light and some fish may not receive sufficient oxygen What aids in reducing erosion? Add more vegetation Why are levees built? Long walls of earth, are built parallel to a river. They are designed to keep the river contained during flooding. Landslide – a massive movement of soil and water, often after heavy rain Water Tables Two forces appear to act on water: gravity and its attraction to other materials There is more fresh water below the Earth’s surface than in all of the lakes, rivers and reservoirs on the surface. This is called ground water. Rocks and soils with large pores between the particles, such as sand and gravel, hold large quantities of ground water. Water infiltrated downward until it reaches an impermeable layer of rock or clay called an aquitard, through which it can travel only very slowly Above the aquitard, ground water fills all the pores in what is called the saturated zone, the upper surface of which is the water table Humans affect the depth of the water table. If more water is taken from wells than falls as precipitation, the water table becomes lower. An aquifer is water trapped in a layer of permeable rock, which itself is trapped between two layers of impermeable rock. Percolation – the process of seeping through a porous material Aquitard – an impervious layer of clay, silt, or rock through which water cannot move quickly Saturated zone – the area beneath the water table where water fills the spaces in the gravel, sand, silt, or rock Water table –the upper boundary of the saturated zone Aquifers – an underground zone of rock or soil that contains and yields water Capillary action – the upward movement of water through soil due to the attraction of water molecules to soil particles Water Treatment o Although water is considered a renewable resource, most is in the oceans and is not suitable for drinking because it contains impurities and must be treated to make it safe to drink. o Many freshwater systems are becoming polluted from dumped sewage, sediments, and wastes o Some impurities are naturally filtered by soil and rock, but soluble substances are not o Most pollutants do not evaporate when water does, therefore they become concentrated in lakes, seas, and oceans, making them even more polluted o Pathogenic bacteria are bacteria that cause bacterial infection o Pathogenic bacteria in human waste can enter water bodies from privies (private sources – toilets, outhouses) or dumped sewage o Coliform bacteria are essential to our health, as they aid the breakdown of the waste products of digestion o A common coliform bacteria is E.coli bacteria which can cause gastroenteritis (symptoms are similar to the stomach flu Acid precipitation When fossil fuels are burned, nitrogen oxides and sulphor dioxide are released into the air. These gases react with water vapor in the clouds, forming droplets of nitric acid and sulphuric acid. These droplets fall as acid precipitation Acid precipitation – precipitation, usually rain or snow, that contains small amounts of sulfuric or nitric acid Industry, vehicle use, and electrical generating plants are the major producers of acid rain Flood Plain – a relatively flat area next to a river’s banks that experiences periodic flooding