That got me thinking about John Muir’s trips to Alaska. Muir is probably best known for his dedication to establishing national parks, especially Yosemite. Geologists in the early 1900s believed Yosemite was the result of a violent convulsion of the earth. Muir stirred up a lot of controversy when he suggested that Yosemite was created by glaciers over a long period of time.
Muir had studied glaciers in Alaska, and his glacial theory proved to be correct.
LESSON PLAN: From Snowflakes to Glaciers
This lesson begins with a true story of one of John Muir’s Alaskan adventures. He became stranded on a glacier with a little dog named Stickeen. Snow was falling, night was approaching, and the only way out was over a precarious ice bridge. It was dangerous for man, but almost impossible for a dog. The story leads into a 15-minute experiment that demonstrates how glaciers are formed when snowflakes are compacted.
[This lesson is adapted from Beyond Penguins and Polar Bears.]
- The book, Stickeen: John Muir and the Brave Little Dog
- 3 large marshmallows per student
- Snow if available
- Potato Masher
- Large (gallon) clear jar
- Read aloud Stickeen: John Muir and the Brave Little Dog. Pay special attention to the illustrations. Christopher Canyon, the illustrator, traveled much of John Muir’s Alaskan route of 1880.Explain to students that they are going to conduct an experiment to see what happens when snow is compacted.
- Give students 3 marshmallows each. Each one simulates a layer of snow.
- Have them put one marshmallow on top of another and measure the height. Then ask them to push down on top marshmallow and measure the height. Have them add the third marshmallow, push down on it, and measure again.
- As students are smashing their marshmallows, ask the “Discussion Questions” below.
- Explain layers of snow lose their air much like the marshmallows.
- If snow is available, conduct a demonstration by filling a jar half way with snow. Ask for a volunteer to smash it down. Continue this until it becomes ice. Add more layers of snow. These additional layers can be tinted with food coloring before being smashed, which will show how they compact.
- For older students explain that the intermediate stage between snow and glacial ice is called firn. It is formed under the pressure of overlying snow by the process of compaction, recrystallization, localized melting, and the crushing of individual snowflakes. This takes about one year. Further compaction of firn at a depth of 150 to 200 feet results in glacial ice.
Discussion Questions: What happens to the marshmallows as you press down on them? What happens to the shape of the marshmallow? What happens to the height of the marshmallow tower?
For the demonstration with snow: Why does the snow turn into ice? (It loses its’ air and changes the shape of the crystal) What force did you use to change the snow into ice? (pressure) How is ice different than snow?
Extension: There is evidence that climate change is causing glaciers around the world to shrink. How We Know What We Know About Our Changing Climate explains this and other climate changes for older elementary students.
Common Core Standards (ELA K-4)
Reading and Literature: Integration of Knowledge and Ideas (K.7, 1.7, 2.7, 3.7, 4.7, 5.7)
Next Generation Science Standards (DCI K-5)
Earth and Space Science
2.A: Earth’s Materials and Systems
2.C: The Role of Water in Surface Processes