Grade by Grade
C. Matter and Energy · Forces Causing Movement

Forces of Nature and Our Environment

C1.1 A1.1 A3.1About 40 minutes
Learning goals
  • I can describe forces from nature, like wind, moving water, ice, snow and earthquakes.
  • I can describe how these forces affect natural environments (forests, rivers, shorelines) and built environments (homes, roads, power lines).
  • I can identify human actions that reduce these effects and human actions that make them worse.
  • I can use a research process to answer a question.

Words to know

natural phenomenon
Something that happens in nature, like a storm, a flood or an earthquake. More than one are called natural phenomena.
natural environment
Places made by nature, like forests, rivers, wetlands and beaches.
built environment
Things people build, like houses, roads, bridges and power lines.
erosion
When wind or moving water slowly carries away soil, sand or rock.
flood
When water covers land that is usually dry.
wetland
Land that is wet and soggy, like a marsh or a swamp. Wetlands soak up water like a sponge.
research
Finding information from trusted sources to answer a question.

Nature is strong!

After a big windstorm, you might see a maple tree lying across a road, branches on the cars, and the power out. Wow, what a push!

Nature exerts huge forces. Today you will learn how these forces change both nature and the things people build, and how people can help.

A large leafy tree lying across a quiet street after a windstorm, its roots and soil pulled out of the ground.
Strong wind pushed hard enough to pull this tree's roots right out of the soil. Nature can exert huge forces on trees and on things people build. AI-generated image

Forces from nature

  • Wind pushes. Strong winds and tornadoes can knock down trees and power lines and tear shingles off roofs. Wind also blows away dry soil from bare fields.
  • Moving water pushes. Rivers and waves carry away soil, sand and rock. This is called erosion. In spring, melting snow and heavy rain can cause floods that push on and damage roads, bridges and basements.
  • Ice is heavy, and gravity pulls it down. In an ice storm, thick ice coats branches and power lines until they bend and break. River ice can pile up and push against bridges and shorelines.
  • Snow is heavy too. Gravity pulls a deep, heavy load of snow down on a roof.
  • Gravity on slopes: heavy rain can loosen soil on a steep hill, and gravity pulls it down in a landslide.
  • Earthquakes shake the ground. Ontario has small earthquakes from time to time, but most are too small to feel.

A real Canadian example

In January 1998, a huge ice storm hit eastern Ontario and Quebec. Thick ice weighed down trees and power lines until many of them broke. Many people had no power for days, and some for weeks. Communities helped each other stay warm.

Force of natureEffect on the natural environmentEffect on the built environment
strong windknocks down trees; blows away dry soilbreaks power lines; damages roofs
moving watererodes riverbanks and shorelinesfloods basements; washes out roads
icebreaks tree branchessnaps power lines; ice jams push on bridges
heavy snowbends and breaks branchespresses down on roofs
gravity on slopeslandslides change hillsidescan damage houses and roads below
How forces of nature change our environments

People can make things better... or worse

Human actions that REDUCE the effects:

  • Planting trees and plants on hills and riverbanks. Roots hold the soil so rain and rivers don't wash it away.
  • Rows of trees (windbreaks) along farm fields slow the wind so it doesn't blow the soil away.
  • Protecting wetlands. Wetlands soak up extra water like a sponge and help prevent floods.
  • Building strong: strong roofs, buildings built to handle wind and snow, and not building houses where floods happen.
  • Trimming trees near power lines, and safely clearing heavy snow off roofs (a job for grown-ups).

Human actions that can make the effects WORSE:

  • Cutting down all the trees on a hill or a riverbank, so nothing holds the soil.
  • Paving over lots of land with roads and parking lots, so rain can't soak into the ground and runs off quickly, causing floods.
  • Filling in wetlands to build on them.
  • Building too close to a river, lake or cliff edge.
strong windrow of trees(windbreak)slower windsoil stays on the fieldfarm field
A windbreak. A row of trees slows the wind, so less soil blows off the farm field.
with plantsbare soil
Rain falls on two hills. On the left, plant roots hold the soil in place. On the right, the bare soil is washed down the hill.
Worked example

Let's research a question

Our research question: How can a town reduce damage from spring floods?

  1. Ask: write the question clearly. What do we want to find out?
  2. Find trusted sources: library books, a trusted website with a grown-up, or ask an expert. In Ontario, conservation authorities help communities plan for floods. First Nations, Métis and Inuit Knowledge Keepers and Elders can share long-held knowledge about the land and water in their area.
  3. Take notes in your own words: wetlands soak up water; trees and plants along rivers slow the water; don't build houses in places that flood; keep storm drains clear of leaves and snow.
  4. Share what you learned: make a poster or a short talk, and say where your information came from.

A town can protect wetlands, plant trees and plants along rivers, keep storm drains clear, and avoid building in places that flood.

Just for fun

Why are trees so good at stopping erosion?

Because they really know how to hold their ground!

Hands-on activity

Erosion model

Do this outside or in a bathtub. You need: two baking pans or plastic trays, soil or sand, a handful of grass clippings, leaves or a piece of old sod, two books, a cup of water, and a watering can or a cup with small holes poked in it by a grown-up.

  1. Fill both pans with the same amount of soil. Pack it down.
  2. Cover the soil in one pan with grass clippings, leaves or sod. Leave the other pan bare.
  3. Prop one end of each pan up on a book to make a slope.
  4. Predict: which pan will lose more soil when it "rains"?
  5. Sprinkle the same amount of water on each pan, from the same height.
  6. Look at the bottom of each pan. Where did more soil wash down? Is the water muddier in one pan?

What to look for: much more soil washes down in the bare pan. Plants and leaves protect the soil, just like trees on a real hillside.

Safety: a grown-up pokes holes in the cup. Wash your hands after touching soil.

Your turn

1

Name three forces from nature.

2

What is erosion?

3

How can a strong wind affect the built environment?

4

How do trees on a riverbank help?

5

How do wetlands help prevent floods?

6

Name one human action that makes flooding worse.

7

What happened in the 1998 ice storm?

More practice: warm-up

1

Is a river part of the natural environment or the built environment?

2

Is a bridge part of the natural environment or the built environment?

3

Which force pulls heavy snow down onto a roof?

4

What do we call it when water covers land that is usually dry?

5

Name one trusted source you could use for research.

More practice: on your own

1

Why do some farmers plant rows of trees along the edges of their fields?

2

In the erosion model, why should both pans get the same amount of water from the same height?

3

A town paves a big field to make a parking lot. Why might this cause more flooding?

4

Name one effect of an ice storm on the natural environment and one on the built environment.

5

Why is it a bad idea to build a house right at the edge of a riverbank?

Challenge

1

A hillside behind a school had all its trees cut down. After heavy rains, mud slid onto the playground. Explain why, and suggest two things the school could do.

2

Write your own research question about a force of nature, and name two sources you would use.

3

Explain how keeping a wetland helps both the natural environment and the built environment.

Check your understanding

Quiz

1.

Which is a force of nature?

2.

When moving water slowly carries away soil, it is called...

3.

Which is part of the built environment?

4.

How do tree roots help a riverbank?

5.

Which human action can make flooding worse?

6.

In an ice storm, why do power lines break?

7.

What is the first step in research?

For parents and teachers

Big idea: Ontario Grade 3 expectation C1.1 asks children to assess the effects of forces from natural phenomena (wind, water, ice, snow, landslides, earthquakes) on natural and built environments, and to identify ways human activities can reduce or enhance those effects. The research example models the scientific research process (A1.1), and the lesson connects science to the community (A3.1).

How to help: After a storm, take a walk and look for effects: fallen branches, washed-out gravel, puddles where water can't soak in. Ask, "What force did that? What could people do to help?" Look up your local conservation authority's website together to see how it helps with floods.

Common difficulties:

  • Mixing up natural and built environments. Ask: "Did people make it?"
  • Seeing people only as the cause of problems. Stress both sides: people can make effects worse, and they can also reduce them.
  • Feeling worried about storms. Reassure your child that communities prepare for storms and help each other, and that following safety rules keeps us safe.

Safety: never go near fallen power lines (stay at least 10 metres away and tell an adult), flooded rivers, or riverbanks during spring melt.