Grade 8 Science Unit 1 - Water Systems on the Earth’s Surface cience/grade8/unit_1_B_grd8_August_ pdf

The Water Cycle Quick water facts: Of the water we can see, 97% is salt water, 2% is frozen in glaciers and ice caps, 1% is fresh water. See Page 8 The average person can survive 3 days without water, 3 weeks without food. We are 60% water.

Water Cycle (See also page 9)

Some Water Cycle Terminology (See Page 9) “The non-stop cycle in which water evaporates into the Atmosphere and returns to the land and oceans” -Water can return to the ocean, soak back into the land (Lithosphere), or be stored in ice for millions of years. -All water, wherever it is found, forms the Hydrosphere -The sun drives the water cycle by causing Evaporation Runoff collects nutrients, pollutants, and dissolved minerals from the land back into the rivers, lakes, and oceans. -Human influence and natural processes affect runoff. The way we interact with the water cycle can affect our lives in positive and negative ways. People spend their lives studying water and the water cycle. Examples are Oceanographers and Hydrologists.

Evaporation When water changes phase from a liquid to a gas. It rises from seas lakes and rivers into the atmosphere when heated by the sun. It rises from the ground and up through plants, carrying nutrients from the roots to the tips.

Condensation Water changes in phase from gas to liquid when it cools. Water droplets and ice crystals form clouds.

Precipitation When moisture in the air falls as rain, freezing rain, sleet, snow, hail etc.

Ground Water Precipitation that falls on the ground and sinks out of sight.

Run off Water that runs from the surface of the land, back into the lakes, rivers and oceans.

Oceanography (Oceanographers) (see also page 20) -The study of the ocean. -Oceanographers use biology, chemistry, geology, math, and physics to study things such as: -Marine life -Waves and currents -Erosion -Sub Ocean (plate tectonics, volcanoes underwater topography)

Hydrology (Hydrologists) -”Study of the movement, distribution, and quality of the water on the earth” - Hydrologists use science to ensure that we have access to easily available clean water. They watch the water cycle carefully and study our impacts upon it. They identify problems and work to find solutions.

-As a class, answer questions on page 13 -What are Hydrologists and Oceanographers and why are their jobs important? -Define Atmosphere, Hydrosphere, Lithosphere. -Define Evaporation, Condensation, Precipitation -Define Gound water and Water Table -Define Runoff. List ways that humans can affect runoff.

Freshwater sources - Lakes, etc. (Page 23) Lakes, or ponds, are basically holes in the ground filled with water collected from precipitation and runoff. Wetlands come on many forms. They are always saturated with water. Marshes are shallow wetlands about 1 metre deep and are wet year round. Streams and rivers are fast flowing waterways. They vary in length, shape, depth, width, speed, temperature and clarity. Different characteristics support different types of life. Groundwater is composed of water that sinks into the land out of site. The height of saturated ground under the surface is called the water table.

Freshwater Sources - Glaciers (Page 23-24) Glaciers occur in areas cold enough to have snow year round. Snow piles up, and forms an ice layer on the bottom. The weight and pressure of the snow and ice melts the bottom layer and causes it to slide downhill very slowly, scraping the ground and moving it downhill. 2/3 of the world’s fresh water is trapped in glaciers. When glaciers flow to the ocean, large chunks break off as icebergs years ago, during the event ice age, most of North America was covered by glaciers. These glaciers were so powerful and heavy the they scraped the tops of mountains off, pushed mountains back down into the crust, carved valleys, and dragged rocks as big as houses (erratics) which were left behind when they melted. Glaciers also dumped huge amounts of fertile ground into the ocean forming rich fishing grounds such as the Grand Banks.

Glaciers (Page 23) 1.Cold environment allows snow to accumulate 2.Ice layer forms at bottom 3.Pressure from above and difference in temperature below causes a layer of water between the lower ice layer and the ground. Water pools and leaks in through cracks. 4.Glacier slides downhill, moving material with it. 5.When glaciers flow into the oceans, pieces break off and form ice bergs. 6.Glaciers and “snow packs” slowly release fresh water. Global warming is causing them to release it too fast.

Glaciers often flow out into the ocean and “calve” icebergs.

Glaciers and global warming (page 25) Glaciers and high mountain snowpacks slowly release badly needed fresh water in the summer months. If glaciers melt too fast, this supply of fresh water does not get refilled in the winter months. California is currently experiencing a similar crisis. They depend upon the fresh water released from melting snow in the summer. Warmer temperatures are causing less snow to collect, resulting in a serious water shortage. Most of the world’s population of humans live at or below sea level and are at risk of losing their homes. Many argue that humans are accelerating global warming and many others argue that it is a normal cycle that we are having little influence over. Few can deny, however, that glaciers are melting much faster than previously recorded history.

A retreating glacier. Note the valley it has carved out.

Another example of retreating glaciers Warming global temperatures are causing glaciers to retreat at an alarming rate, releasing fresh water at an unnatural rate. How does this affect Humans? Land plants and animals? Aquatic plants and animals?

Glaciers change the landscape. In addition to gouging out valleys, glaciers have shaved the tops off of mountains, pushed the crust back into the earth and moved surface materials for large distances. This is an “erratic”. It is a large rock deposited on the ground by a retreating glacier during the last ice age. Rocks like this liter the barrens along the TCH between you home and St. John’s. On the west coast of Newfoundland, people digging house foundations a kilometer inland on dry land hit beach rocks? Why?

Drainage Basins (page 26) Also called Watersheds Areas of land that drain into a body of water. The body of water can be a river, lake, pond or ocean. This water drains because of gravity and water washes materials from these basins into larger bodies of water as runoff.

Run off ( Page 27) We previously discussed runoff as water that runs off the, due to gravity, into bodies of water such as lakes, rivers, and oceans. Runoff can be affected by the type of ground. It runs over non-porous rock slower. It is released by marshlands slowly. House building removes vegetation, drains marshes, and creates non-porous streets. Heavy rains generate more runoff. Usually the natural environment can handle this but.... -Recently, rivers of water flowed through the Avalon Mall because the artificial drainage of storm sewers could not keep up with the development of housing. Vegetation also stabilizes slopes. Hills and banks stripped of plants can collapse under rain that they would normally withstand. There are many cases of landslides killing people in Newfoundland throughout our history. -The unnatural wastewater that we release can have negative effects upon the environment. Few parts of the world treat their waste before it is washed into the ocean and sewer systems often overflow into streams. Water treatment does not remove all harmful chemicals such as birth control hormones.

1.Define lake, wetland, stream, groundwater, water table. 2.How does a glacier form? 3.Why are glaciers important? 4.How does the effect of global warming upon glaciers affect us? 5.Why is it important to know what a drainage basin is and where they are? 6.What kinds of drainage basins are important to us? 7.What is runoff and how does it affect drainage basins?

Fresh Water, Salt Water, Salinity (page 14) All natural water has tiny amounts of salts and minerals dissolved into it. Fresh water has 1/200 th the amount that Salt Water has. Salt water has 35g of salt for every liter of water. Salts and minerals wash off the land and into the oceans (page 16), where they remain and concentrate due to evaporation. Run off goes into other water basins but they are regularly flushed out. The amount of salt and minerals dissolved into water is called Salinity. 85% of the dissolved material in salt water is Sodium Chloride (page 16).

Density (page 17) Denisty is the amount of mass of a substance in a certain volume. The more “packed” the substance with molecules, the more dense it is. Objects that are more dense will sink in a less dense medium and objects that are less dense will rise or float in less dense medium. Warming substances moves molecules apart and makes them less dense. That is why warm air rises, cool air sinks, warm water rises, and cool water sinks. Salt water is more dense than fresh water and is more “packed” with molecules (remember that fresh water has 1/200 th the salt that salt water has in it). Therefore, we float easier in salt water. Because salt water is more dense, it will sink in fresh water.

Freezing Point (page 17) Freezing point is the temperature at which a liquid turns into a solid. Freezing point is a property of a substance. Fresh water freezes at 0 degrees Celsius. Mixing different substances changes their properties. Mixing salt with water lowers its freezing point.

Salt water vs Fresh water

1.What is salinity? 2.Why is salt water more dense than fresh water? 3.What is density? 4.How can temperature affect density? 5.In what ways is Salt Water different from Fresh water?