Geoscience Weathering and Erosion yrs 4 - 7
Weathering - When rocks are worn down by water,
wind, or other means, that is weathering. Soil is made up
of weathered rock particles, so without weathering, there
would be no soil. Try the following activities to see how
rocks can weather.
1. How Do Chemicals Weather Rocks?
Day 1
Place an equal number of limestone chips in each of two jars. Cover the
stones in one jar with water and those in the other with vinegar; then screw
lids on the jars. Allow the jars to stand overnight. You may notice some
bubbles forming in the jar with the vinegar. (What might the bubbles
indicate?).
The next day
Pour out the liquid from each jar into separate bowls. Label the bowls
"water" and "vinegar". Compare the amount of solid material remaining in
the two bowls.
2. How Do Streams Weather Rocks?
Place some small, freshly broken pieces of rock or brick in a large plastic
jar. Softer rocks such as sandstone or limestone work best. Fill the jar about
halfway with clear water. Put aside some other pieces of the broken rock.
Close the lid of the jar and shake it 1,000 times or shake for about
30minutes. Remove the rocks and note any changes in their appearance
compared with the rocks that were not shaken. Describe these changes.
Filter the water through a piece of filter paper or funnel lined with paper
towels. What do you see in the filter paper? You may want to experiment
with different types of rock to see what types will change more. What might
happen to rocks in a stream?
3. How Does Ice Weather Rocks?
Completely fill a glass jar with water and cap it tightly. Place the jar in a
resealable plastic bag, or coat in cement and allow it to dry. Record your
experiment using a digital camera. Place the bag in a cardboard box Put the
box and the bag in a freezer overnight. ASK YOUR TEACHER TO
REMOVE THE PLASTIC BAG AND JAR (it will be broken). Teachers
will handle and dispose of the broken glass carefully. What might this
demonstration tell us about rocks and weather?
Erosion - When particles weathered from rocks are
carried away, it is called erosion. Erosion is responsible
for wearing down exposed places and depositing
sediment in level places.
4. What Happens To A Mountain?
Build a "mountain" of soil 50 cm high in an undisturbed location in your
school grounds. Observe the mountain once a week for three months.
Measure your mountain’s height and width. Draw a picture of your
mountain on 1cm square graph paper using a scale: .5cm =1cm and note any
changes in its surface. After observing the mountain for an extended period
of time, suggest what forces might have caused changes in your mountain.
How long do you think the mountain would remain if you left it there?
5. How Does Vegetation Affect Erosion?
Punch holes in the bottom of a plastic cup to make a sprinkler. Place three to
five centimetres of soil in each of two planting trays. Sprinkle grass seed on
the soil in one of them and cover lightly with soil. Water both trays every
day with the sprinkler until the grass is five centimetres tall. Prop the ends of
both trays up at a moderate angle with bricks or blocks. Sprinkle each tray
with water equally until you observe soil erosion. In which tray did the soil
erode more? What might be the effect of removing plants like trees from a
steep mountainside? How could soil erosion be controlled in steep places?
What other factors can you think of that would affect the amount of erosion?
Identify any areas in your school grounds that are steep. Take a walk around
the grounds and photograph signs of erosion.
6. Wave Action - How Beaches Are Formed
Slope a generous amount of sand against one end of a large square sand tray.
Add water until the sand is about half covered. Use a ruler shaped piece of
wood to generate steady, even waves in the tray. Observe the action of the
waves on the sand. They should see that the water removes sand from the
upper part of the "beach" and deposits it below the waterline. This is how
sandbars and barrier islands are formed. If you can make very small, rapid
waves, you may see that the sand is redeposited on the beach. Record your
experiment with a digital camera.
7. How Does Water Carry Particles of Rock and Soil?
Mix some gravel, sand, mud, silt, and clay in a large jar. Add water to the
jar. Cover the jar with the lid; then shake the jar vigorously. Observe and
photograph the jar over a period of time and note how long it takes for the
different materials to settle on the bottom. Do you see different layers on the
bottom? What is different about them? Think about different kinds of
streams and rivers. Where would you expect to find a rocky or gravel
bottom? Where would there be a muddy or silty bottom? Which type of
material might be carried for the longest distance? (The smaller particles
remain in suspension in the water for the longest time. They have a larger
ratio of surface area to mass and therefore experience more resistance from
the water as they sink.)
8. Model of the Grand Canyon
Cut out the middle section of one of the short sides of a cardboard box. (The
lid of a reflex paper box works well.) Line the box with a plastic bag. Cover
the bottom of the box with a layer of mud or wet soil. . Cover this layer with
another layer of different colour sand. Repeat with many layers until the box
is full; allow a week for the layers to dry. Then tilt the box under an outdoor
hose with the open end downward, and run water in a steady stream onto the
top end. Observe how a canyon is formed. Describe the effect the different
layers have on the erosion of the canyon.
Websites
http://www.consrv.ca.gov/CGS/information/3D_PaperModels.htm super
site for geo science lots of 3D models to make out of paper. The trilobite
is my favourite.
Weathering Explanation
How Do Chemicals Weather Rocks?
The bowl that contained vinegar will have a larger amount of solid material.
(Limestone, marble, and other carbonate rocks react with acid to form
carbon dioxide and soluble salts. Rainwater is often acid and can erode
limestone easily. Acid groundwater dissolves limestone underground,
forming caves and sinkholes. Extension: Examine other types of rock to see
if they react to vinegar in the same way as carbonate rocks. Try Marble.
Weathering Explanation
How Do Streams Weather Rocks?
(Rocks in streams are weathered by water and movement.)
Weathering Explanation
How Does Ice Weather Rocks?
(When water freezes, it expands. When it freezes in cracks in rocks, the
expansion can cause the rock to break.)
Water is peculiar. When most substances change from liquid to solid
form, they shrink together, become denser, their molecules packed most
closely together.
But when water changes from a sloshy liquid to solid ice, it expands,
becomes less dense. Which is why ice floats to the top of your Coke,
rather than sinking like a stone to the bottom?
Other real-world results: Water pipes freeze and burst in unheated houses.
Water collects in roadway cracks in winter, turns to ice, and enlarges
crevices into gaping potholes.
If frozen water weren't less dense than liquid, there would be no floating
icebergs to sight off the bow of a ship. There would be no skating on icecovered ponds, while fish and other life shelter in insulated water below.
If water froze from the bottom up, much of Earth's water would solidify
in winter, and life might be impossible.