• Wind is blowing sand across the surface.
• Over time, piles of sand begin to form hills.
• The sand changes shape from Day 1 to Day 197.
• The sand dunes get larger as more sand collects.
• Grasses begin to grow on the sand dunes and help hold them in place.

EXTENDING THE DISCUSSION
After the observational question, randomly call on one or more students to share what they or their partner answered. Then ask the class, “Did anyone notice…?” using the suggestions above or anything else you’ve noticed.

• Where did the sand originally come from?
• Why does the sand pile up in certain places?
• How long does it take for a sand dune to fully form?
• What would happen if the wind stopped blowing?
• How do grasses keep the sand dunes from moving?

EXTENDING THE DISCUSSION
After students have shared what they notice, ask the class, “Did anyone wonder…?” using the suggestions above or anything else you might think is interesting or relevant to the lesson.

To the observational question, How do sand dunes form?

LOW-LEVEL

Sand dunes form by wind blowing sand into piles.

HIGH-LEVEL

Sand dunes form by wind causing erosion that moves sand and deposition that builds it up into a landform over time.

RESPONDING TO RESPONSES
Emphasize and celebrate each student’s use of the key vocabulary to support a culture of “no wrong answers.”