EDGEO WORKSHOP WET AND WILD: WATER SYSTEMS, WEATHERING AND EROSION GRADE 8: WATER SYSTEMS ON EARTH
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EdGEO Workshop
Wet and Wild: Water Systems,
Weathering and Erosion
for
Grade 8: Water Systems on Earth
March 27th 2010
Catalyst 2010
Eileen Van der Flier-Keller
School of Earth and Ocean Sciences, University of Victoria
and Pacific CRYSTAL
fkeller@uvic.ca or 250 472-4019
0Workshop Schedule
This hands-on workshop will explore activities and demonstrations to meet
the needs of the Grade 8 Earth and Space Science Curriculum. Discover the
importance of groundwater. See what makes the oceans salty. Find out how
weathering and erosion shape the landscape we see around us.
Activity 1 – Where on Earth is the Water?
Activity 2 – Freshwater, usable water for humans
Activity 3 - Groundwater
Activity 4 - What’s the difference between freshwater and saltwater?
Activity 5 – Weathering, and why the ocean is salty
Activity 6 – Erosion
Curriculum Links:
Grade 8 Water Systems on Earth
• Describe the world distribution of water
• Identify similarities and differences between salt water and fresh water
• Define weathering and erosion
• Describe how the movement of water transports weathered material
• Describe the impact of water movement and surface features (e.g. weathering,
erosion, deposition)
Resources:
Field Guide to the Identification of Pebbles
Workshop Manual
Rock sample
Hydrologic Cycle diagram
Acknowledgements:
Thanks to EdGEO for a grant to support this workshop and provide the take-home
resources.
1Activity 1 – Where on Earth is the Water? Leading Qs Q. Use a world map or globe as a basis for identifying where the major water reservoirs on Earth are. Q. Which water reservoirs are not visible on the map or globe? Q. How do we know there is water in these ‘not so visible’ reservoirs e.g. air, soil? Q. Suggest what you think the distribution of water is between all of these reservoirs Demonstration: Demonstrate the proportions of water in each of these reservoirs, using the table below, by filling a 100ml graduated cylinder. If all the Earth’s water were symbolized by 100ml of water, add water to the cylinder to represent each of the reservoirs i.e. 97.2ml in the oceans, 2.15ml in glaciers (and ice caps) and the rest i.e.
Activity 2 – Freshwater, usable water for humans
Leading Qs:
Q. Why do we need freshwater?
• all life depends on water (no life on the moon, Mercury or Venus because there is
only water vapour, Mars only ice).
• Growing our food e.g. vegetables, animals. For example you need 1000kg of
water to grow 1kg of potatoes.
• Each of us is two-thirds water. Every day humans must replace 2.4 litres of water
(that we lose from our bodies) by drinking and by our body taking water from the
food that we eat. Our blood is 83% water – imp for digesting food, taking in
oxygen, controlling body temp, getting rid of waste
Q. Where is the freshwater on the planet?
Where do you think humans get most of their water from?
Activity:
1. Use the Table below to fill the graduated cylinder again, this time only
representing the freshwater reservoirs i.e. 84.9ml ice sheets, 14.2ml groundwater
If you wish to give the students a math link to this activity, have them calculate
the relative proportions of freshwater using the table in Activity 1.
TABLE: Fresh Water in the Hydrosphere (USGS 1987)
Parts of the Volume of fresh Share of total Rate of
Hydrosphere water (km3) volume of Water
freshwater (%0 Exchange
Ice sheets and glaciers 24,000,000 84.945 8000 years
Groundwater 4,000,000 14.158 280 years
Lakes and Reservoirs 155,000 0.549 7 years
Soil Moisture 83,000 0.294 1 year
Water Vapour in the 14,000 0.049 9.9 days
Atmosphere
River Water 1,200 0.004 11.3 days
Total 28,253,200 99.999
Note: You will find many different estimates of global water distribution
Q. What do you notice about how our freshwater is distributed?
Q. Which of these reservoirs are the most practical and accessible for humans to use?
3Activity 3 - Groundwater
Groundwater: represents a vast amount of freshwater (and saline water) that is mostly
unseen, which exists in the ground, and moves as part of the hydrologic cycle.
Occasionally we see groundwater emerging at the surface as springs. Rain falls on the
land, and while some of it flows away overland in rivers, into lakes and finally to the sea,
some sinks into the ground (we can see this happening when we water our gardens in
summer) seeping into the sediment and rock below to become groundwater. This water
moves slowly downslope and eventually emerges into rivers or the ocean.
Cool fact: The water cycle has been going on for ever (since there was land and
liquid water), and it is the same water that is cycling around over and over. This
means that there is a good chance that some of the water molecules in our water
were drunk by a dinosaur or passed through the earliest fish over 400my ago. We
are drinking the same water as the ancient Greeks.
Leading Q: Where is the groundwater below the Earth’s surface? When we talk about
groundwater flowing, does this mean there are rivers flowing under our feet?
Porosity demonstration:
Most groundwater is held in tiny spaces (porosity) between the minerals or fragments in
rocks or sediment.
1. Examine the sandstone sample and discuss whether you think there is room inside to
hold water?
2. To demonstrate porosity use glass beads or polished stones in a plastic cylinder and
pour water in from a measuring cup. Using the original measurement of water in the
cup, subtract the amount left after filling the spaces in the container to determine how
much porosity exists between the stones.
3. Using an eye dropper to add a small amount of water on top of a variety of rock
types. Drop the same rocks into a cup of water. What happens? Do any of them
bubble (showing air being expelled and replaced by water)? If so, there is porosity
which is now filled with water.
4. How would you determine which rock type would be best for holding most
groundwater.
Groundwater Use Qs:
Q. Who in Canada uses groundwater as opposed to surface water.
In Victoria we get our water from the Sooke Reservoir. In the countryside around
Victoria many households and farms get water from wells i.e. groundwater.
What about farms in the Prairies and in the Interior of BC?
There are whole cities in Canada that get their water from underground e.g. Hamilton
Ontario. And provinces e.g. PEI (Anne of Green Gables)
Bottled water is spring water which is from groundwater.
So, keeping the groundwater aquifers clean is very important.
Q. Discuss potential ways we may be adding salt to our groundwater?
e.g. salt on roads, crop irrigation evapotranspiration
4Activity 4 - What’s the difference between freshwater and saltwater?
Leading Qs.
Q. What do we mean by freshwater or salt water or brackish water?
Fresh water: < 1000 ppm dissolved salts – use tap water
BrackishActivity 5 – Weathering Why are the oceans salty?
Leading Q. Why do you think the ocean is salty?
Activity:
1. Experiment with samples of halite and limestone to see if they will dissolve in
water. What did you observe happen?
What happens if you add a tiny amount of acid to the water?
2. Examine the large rock samples provided. Some have been exposed at the Earth’s
surface for a long time, others very recently. Can you tell which have been more
recently exposed? What do you notice about each of these samples? IDEA: A
good field location to observe weathering (especially to determine weathering
rates) is any local graveyard.
3. Weathering processes have acted on these rocks. Note all the effects and features
which may be related to weathering e.g.
a. Some entire parts of the rock are dissolved
b. for some rocks certain minerals dissolve out
c. some rocks start to crumble and break apart
d. some minerals turn into others e.g. clays or iron oxides
e. some rocks have lichen etc growing on them
Demonstration:
A coffee filter system can be used to model what can happen (d) during weathering.
Set up the coffee filter and observe what happens when you pour hot water
through the filter. This is an analogy for what happens to rocks when water
interacts with them.
Q. What do you notice about the coffee grounds after the water has passed?
Q. What happened to the water?
What you are seeing are all the effects of weathering. Water is a very important
contributor to weathering (especially chemical weathering, but also to freeze thaw – a
form of physical weathering).
Definition of Weathering: Weathering is the physical breakdown (or disintegration) and
chemical alteration (or decomposition) of rocks IN PLACE i.e. at or near the Earth’s
surface, by physical, chemical and biological processes.
Weathering produces a lot of dissolved ions in water (from a, b, d, and e). These
dissolved constituents are carried to the ocean in rivers and groundwater and over time
make the ocean salty. The other contributor to ocean salinity (dissolved salts) is
submarine volcanism e.g. at hydrothermal vents.
Q. Is the ocean getting saltier?
6Important Related Water Characteristic:
Water is an excellent solvent – it has a very strong attraction to surfaces on minerals,
rocks and other materials which allows dissolution (i.e. water dissolves many substances)
– it is often referred to as the Universal Solvent. Water dissolves many types of minerals
and rocks during weathering.
This means that water carries a wide range of dissolved substances and nutrients (which
can make water taste salty). Dissolved substances make water essential for almost every
biological and geochemical process.
TABLE: Dissolved Ions in River Water and Sea Water
Dissolved Ion River Water ppm Seawater ppm
(parts per million) (parts per million)
Carbonate/bicarbonate 58.8 140
Calcium 15 420
Silica 13.1Activity 6 – Erosion
Leading Q: What is the difference between weathering and erosion?
Definition of Erosion:
Erosion is the physical removal of weathered materials i.e. rock and soil, by agents such
as water, wind, ice or gravity.
Activities:
Try the following activities – instructions attached (from Earthlearningidea.com)
• Rock, rattle and roll: Investigating the resistance of rocks to erosion by shaking in
a plastic container
• Mighty river in a small gutter: Sediments on the move
Related Activity: Sedimentary rocks from weathering and erosion
1. On the gutter river, have students point out where erosion took place.
Can you see any evidence of deposition?
These are the kinds of situations in which sediments – which eventually turn into
sedimentary rocks – are deposited.
2. Place the sedimentary rock samples on the experiment in the places where you
think they might have formed.
Q. What might the relationship be between grain size (conglomerate, sandstone,
mudstone) and position on the river system?
Use the Pebble Guide to consider the whole range of common sedimentary rocks These
are rocks that form at the Earth’s surface from weathering and erosion. Can you fit them
all into the river system?
What ones can’t you? How might these have formed if not by erosion of weathered
particles in a river (or by wind or ice).
Limestones do form from weathering products, but not from the solid pieces that are left
over like sandstones, mudstones and conglomerates. Limestones form from the dissolved
ions in water reprecipitating because of the activity of organisms. Organisms like corals,
shells, plankton are responsible for drawing the ions out of seawater and producing the
mineral shells and coral reefs that end up in limestones. Mineral recycling!
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