History & Geography · Grade 7 · Physical Patterns in a Changing World · Term 2

Erosion and Deposition by Water, Wind, Ice

Examine how water, wind, and ice transport and deposit weathered material, shaping landforms.

• Ontario Curriculum Expectations
• ON: Physical Patterns in a Changing World - Grade 7

About This Topic

This topic explores the dynamic forces of erosion and deposition, focusing on how water, wind, and ice sculpt Canada's diverse landscapes. Students will investigate how these agents of change transport weathered materials, from fine silt to large boulders, and where they deposit these materials, creating new landforms. Key Canadian examples include the dramatic U-shaped valleys and moraines left by glaciers in the Canadian Shield and the Rockies, the intricate deltas formed by major rivers like the St. Lawrence, and the coastal erosion shaping the shores of the Atlantic and Pacific oceans.

Understanding these processes is crucial for appreciating the geological history of Canada and predicting future landscape changes. Students will analyze how human activities, such as deforestation or urbanization, can exacerbate erosion or alter deposition patterns. This unit connects directly to the physical geography of Canada, helping students understand the origins of familiar landforms and the ongoing processes that continue to shape them. Active learning, through mapping, modeling, and field observations, makes these abstract geological processes tangible and observable.

Active learning benefits this topic by allowing students to directly engage with the physical processes of erosion and deposition. Building models of river deltas or observing wind erosion in a classroom simulation provides concrete experiences that solidify understanding. This hands-on approach moves beyond textbook descriptions, fostering deeper comprehension and critical thinking about how these forces shape our world.

Key Questions

1. Analyze how glaciers have sculpted the Canadian Shield and other regions.
2. Explain the role of rivers and coastlines in shaping Canada's geography.
3. Predict the impact of increased wind erosion in arid or deforested areas.

Watch Out for These Misconceptions

Common Misconception

Erosion only happens quickly and dramatically.

What to Teach Instead

While dramatic events like landslides occur, erosion is also a slow, continuous process. Hands-on modeling of river or wind erosion over time, even in a short period, helps students see both rapid and gradual changes. Discussion can highlight how these slow changes accumulate to form major landforms.

Common Misconception

Deposition is simply where things 'end up' after being moved.

What to Teach Instead

Deposition is an active process where eroded material is dropped by a transporting agent. Building a delta model clearly shows how water velocity changes lead to specific deposition patterns. Students can observe how different particle sizes are deposited in different locations, demonstrating sorting.

Common Misconception

Only water causes erosion.

What to Teach Instead

Students often focus on water's role due to its visibility. Introducing wind and ice erosion simulations, like the hairdryer activity or examining glacial landform maps, broadens their understanding. Comparing the results of different erosion types highlights the distinct impacts of water, wind, and ice.

Active Learning Ideas

Model: River Delta Formation

Students build a small-scale model of a river flowing into a larger body of water using sand, gravel, and a water source. They observe and record how sediment is deposited as the water slows down, forming a delta.

60 min·Small Groups

Simulation Game: Wind Erosion Tray

Using a shallow tray filled with sand and small pebbles, students use a hairdryer on a low setting to simulate wind. They observe how different wind speeds and angles affect the movement and deposition of sediment.

45 min·Small Groups

Concept Mapping: Glacial Landforms in Canada

Students use topographic maps and online resources to identify and label examples of glacial landforms (e.g., cirques, moraines, drumlins) in specific Canadian regions, such as the Canadian Shield or the Rocky Mountains.

50 min·Individual

Fishbowl Discussion: Coastal Erosion Case Study

Present students with a case study of coastal erosion in Canada (e.g., Prince Edward Island's red cliffs). Facilitate a whole-class discussion on the causes, impacts, and potential mitigation strategies.

30 min·Whole Class

Frequently Asked Questions

How does glacial erosion shape the Canadian Shield?

Glaciers are powerful agents of erosion. As massive ice sheets moved across the Canadian Shield, they scraped away soil and bedrock, carving out valleys and basins. When the glaciers melted, these basins filled with water, forming the countless lakes characteristic of the Shield region. The deposited material, called till, also created features like moraines.

What is the difference between erosion and deposition?

Erosion is the process of wearing away and transporting rock and soil by natural agents like water, wind, or ice. Deposition is the process where these transported materials are dropped or settled in a new location. Think of erosion as picking up and moving, and deposition as putting down.

How can students actively investigate wind erosion?

Students can simulate wind erosion using a tray of sand and a hairdryer. By varying the hairdryer's distance and speed, they can observe how wind moves sand particles and creates small dunes or blowouts. This hands-on activity provides a tangible understanding of wind's erosive power and depositional patterns.

Why is understanding erosion and deposition important for studying Canada's geography?

These processes are fundamental to understanding how Canada's diverse landscapes were formed and continue to change. From the mountains carved by glaciers to the river valleys and coastlines shaped by water, erosion and deposition explain the physical features students see. Recognizing these forces helps explain regional differences and predict future environmental changes.