Download Grade 8 Quiz Review #2 – Water Systems

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