Hands-On Activity: Glacier Movement Demo
Big Idea:
Glaciers are rivers of ice that carved much of the modern landscape of the Northern Hemisphere. They created the Great Lakes, shaped mountain valleys, deposited boulders far from their origins, and lowered sea levels enough to expose land bridges between continents.

Materials:

• A large tray, baking dish, or shallow bin
• Damp sand, soil, or kinetic sand
• Small rocks, pebbles, or gravel
• A large block of ice (freeze water in a bowl or container ahead of time)
• Optional: food coloring mixed into the ice to visualize meltwater
• Paper towels

What to Do:

Step 1: Set Up the Landscape
Spread a thick layer of damp sand across the tray. Press small rocks and pebbles into the surface in scattered locations. "This is the landscape before the glacier arrives: hills, rocks, valleys."

Step 2: Set the Scene
"During the Pleistocene Ice Age, glaciers up to 3 kilometers thick covered much of North America and Europe. They moved only a few meters per year, but over thousands of years, that slow movement had enormous power. The ice was so heavy that it actually pushed the bedrock down beneath it."

Step 3: Start the Glacier
Place the ice block at one end of the tray. Gently push it forward slowly, or tilt the tray slightly. Let it move across the sand.

Step 4: Observe and Record
Ask learners to watch for and record on the lab sheet:

• Scratches or grooves carved in the sand
• Rocks being pushed forward by the glacier
• Sediment building up at the front edge (this is called a moraine)
• What happens when the ice melts at the far end (meltwater deposits)

Step 5: Identify the Features
Name each feature:

• Grooves and scratches = glacial striations
• Pushed rock pile at the front = terminal moraine
• Sediment deposited to the sides = lateral moraine
• Basins carved in rock that later fill with water = lakes

Step 6: The Great Lakes Connection
"The Great Lakes were carved by glaciers exactly like this one, just incomparably larger. The basins were gouged by advancing ice and then filled with meltwater as the glaciers retreated."

Step 7: Discuss

• Sea levels dropped by about 120 meters during the last glacial maximum. What land would be exposed that is underwater today? Where could people have walked that is now ocean?
• What caused the ice ages to begin and end? (Milankovitch cycles, changes in Earth's orbit and axial tilt.)

What's Really Happening (Caregiver Explanation):
The Pleistocene Ice Ages were not a single event but a series of glacial and interglacial periods driven by cycles in Earth's orbit and axial tilt: the Milankovitch cycles. During glacial maxima, ice sheets covered roughly a third of Earth's land surface, lowering sea levels by up to 120 meters and exposing continental shelves as dry land. The Bering Land Bridge that allowed humans to cross from Asia to the Americas existed during these low sea level periods. When the glaciers retreated, they left behind entirely reshaped landscapes: the Great Lakes, Scandinavia's fjords, the Scottish Highlands, and most of the flat agricultural land of the northern United States and Canada were all directly shaped by glacial erosion and deposition.

Digging Deeper:
Research how the Great Lakes of North America were formed by glacial activity. Then look up the Milankovitch cycles, the three changes in Earth's orbit and tilt that scientists believe are responsible for triggering ice ages. What are the three cycles, and how long does each one take? Why do scientists believe these orbital changes cause ice ages rather than just temperature fluctuations?