Teaching overview
Learning points
- Two million years ago, what is now Yosemite National Park in California was covered in mountains and V-shaped valleys, which had been carved out by rivers.
- During an ice age, the valleys filled with slow-moving rivers of ice called glaciers.
- As the glaciers moved through the valleys, they wore the rock away, turning the V-shaped valleys into the steep-sided, U-shaped valleys we see today.
Curriculum keywords
- Geology
- Landforms
- Glaciers
Multimedia toolbox
El Capitan visual
Show the visual before the video and ask students to describe what they can see. How could a person reach the top of the rocks?
Mountain climber visual
Show the visual after the video to spark a discussion about the safety precautions and equipment a climber uses to prepare to climb El Capitan.
Glacial valley visual
Show the visual of glaciers in a valley in Canada to illustrate the enormous power of these slow-moving rivers of ice.
Spark a discussion
- Why do climbers like to climb El Capitan?
- What makes El Capitan a challenging climb?
- Why do steepness and smoothness make something more difficult to climb?
- What is an Ice Age?
- How do we know what landscapes looked like millions of years ago?
- Are landscapes still changing today?
- What are some examples of slow landscape change?
- In what ways can landscapes change very quickly?
Activities
Modelling erosion
CONSTRUCT models of landscapes and test the effects of erosion caused by water, wind and glacial movement.
Other activity ideas
- INVESTIGATE landforms in the local area – such as valleys, caves and cliffs – that were created by erosion over time.
- WRITE a story about being a climber preparing to tackle El Capitan. What safety equipment do you need? How do you train? How do you feel about the challenge?
- RESEARCH the area where El Capitan is found. What is interesting about Yosemite National Park? What wildlife lives in it? What other natural features does it contain?
Modelling erosion
Duration: 30 minutes
Resources:
- (per group):
- 3 shoe boxes or similar containers
- Soil
- Water in a spray bottle
- Drinking straws
- Ice cubes
Key Learning:
This activity allows students to set up their own models of water, wind and glacial erosion, seeing these processes in action on a small scale.Activity instructions:
- Organize students into groups. Give each group the resources listed above.
- Tell students to arrange the soil into a slope against one side of each container.
- First, students should use the water in their spray bottles to represent water erosion. They should spray the water onto the top of the soil slope in one container. Ask students to observe what happens. The water should run down the slope, displacing some of the soil and creating a small channel.
- Next, students should use the drinking straws to represent wind erosion by blowing onto the soil in another container. Students should observe that the "wind" blows some of the soil down the hill.
- Finally, students should use the ice cubes to represent glacial erosion, placing them at the top of the slope in their remaining containers and pushing them down. Students should observe that the ice makes the soil move even more than the water or wind did. The ice cubes are like small glaciers carving out deep ridges in the land.
Optional extra
Students could test the differences changes in the environment make to the amount of erosion produced by water, wind and glaciers. What happens when the soil is arranged flat rather than in a slope? Does adding objects to represent, for example, trees affect the erosion that is caused?
Background information
- Landscapes are not fixed. They are constantly changing through processes that can take place quickly (e.g. volcanic eruption, landslides) or slowly (gradual erosion).
- Erosion is the breaking down of rocks and soil through natural forces. The broken-down material is carried off by the forces that erode it and deposited elsewhere.
- Rivers form part of the global water cycle, and their main role is to drain the land and return water to the sea. The start of most rivers is found in hills and mountains, and river erosion occurs as water moves downstream to the mouth of the river.
- Glaciers – rivers of ice – appear on all Earth’s continents, with the exception of Australasia: even in Africa, they are found high in mountains. In Antarctica, the glacial ice is so thick that only the highest mountains poke through. In fact, more than 75% of the world’s fresh water is locked up in glaciers.
- Glaciers form when ice and snow builds up faster than it disappears. The solid mass of ice and rock flows downhill under its own weight – too slowly to see with the naked eye, but time-lapse photography reveals a continuous, fluid motion.
- Glaciers change landscapes through three main processes: removing material, moving material and dumping material.
- Rocks are slowly worn away as water freezes in cracks and holes, widening gaps and eventually forcing them apart.
- At the base of a glacier, the passing ice freezes to the rock surface and pulls chunks of it away, leaving a jagged surface. These fragments grind away at the underlying rocks like sandpaper.
Glossary
- Glacier
- A very large, slow-moving river of ice.
- Erosion
- The process of wearing away an object over a period of time, caused by various environmental and weather conditions.
- Ice Age
- A very long period of time when the Earth’s temperature is reduced, resulting in the growth of ice sheets and glaciers.
- Valley
- A long, low area between hills or mountains.
Twig Science: A Complete Pre-K–8 Program for the NGSS
Immersive Investigations with High-Quality Multimedia
- Investigating, designing, building, and understanding phenomena
- Hands-on, digital, video, and print investigations
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