TOPIC: EROSION GRADE: 2
STANDARD: 2 ESS.3
Small plastic tubes to make small sand towers
Plastic lids or trays to catch wet sand
Cups for water
Pipettes (water droppers)
Hand lenses or magnifying glasses (to look carefully at the sand)
Time needed: 30-45 minutes
Engage: Remind students of the three important things that scientists do: 1) Observe, 2) Measure, and 3) Communicate. Tell them that today they will be doing all three of these things by exploring what water drops do to towers of sand.
Hand out the Sand and Water Erosion Recording Sheet. Tell students that they will need to be good scientists by carefully observing what they see, drawing pictures, and writing to communicate.
Before handing sand towers, lids, hand lenses, and rulers, show students how to turn over and release the sand from the tubes by tapping and squeezing (just like they would do building a sand castle).
Important: Also demonstrate how to use the pipette to “suck up” water and squeeze out small drops on top of the sand tower. (Some students may find this challenging, and will squeeze too hard releasing an entire pipette full of water on the tower, so I emphasize to make gentle, tiny squeezes that make small drops of water.)
Hand out sand towers, lids, hand lenses and rulers to pairs of students. (Do not give them water until they pop out their towers and carefully observe them with the hand lenses.) They also need to draw a picture and use words to describe what they see in box #2 on the Sand and Water Erosion Recording Sheet.
Encourage students to make predictions about what they think will happen when they begin to drop water on the towers of sand.
Explore: After students carefully observe and draw a picture of what the sand tower looks like and use words to describe what they see (including a measurement of how tall and wide the tower is), hand out a cup of water and pipette to each pair of students.
Instruct students to take turns dropping and counting 20 drops of water onto the tower, stopping after each 20 drops to observe, draw, measure, and write about what the sand tower looks like.
Explain: When students have finished dropping all 40 drops of water and have pictures and measurements, discuss the changes students noticed. Some students may have tried to drop the water drops carefully so that the tower did not fall, and others might noticed that the tower fell and is “mushy” or “slushy.” Discuss how neither are wrong, and talk about why different results were achieved.
Ask students if they notice any similarities in what happened to their towers and what happens to bare dirt or ground when it rains. Talk about how gentle rain may “sink’ into the dirt, and barely wash away any of it, but how more aggressive harder rain makes puddles and streams that wash away dirt and particles to other areas.
Tell students that this “washing away” of particles from the surface of the Earth is called erosion. Erosion is a natural process, or something that happens without humans, but we can upset this balance by farming, logging, and construction. The unbalance can cause too many particles to wash away, and we can lose too much soil too fast.
Wind and ice also cause erosion.
Ideas for Elaborating Further (Optional):
Read the books:
Soil Erosion and How to Prevent It by Natalie Hyde
Erosion: Changing Earth’s Surface by Robin Koontz
After students conduct their sand tower experiments, give them all suckers and tell them they were good scientists. Tell them not to bite the suckers, but instead to lick and suck on them as they watch a short movie.
Show them the movie, Billy Blue Hair- What is Erosion? Find the movie here on YouTube: https://www.youtube.com/watch?v=G5Rp9MJJGCU
As they watch the movie, sucking on the suckers, they will come to realize that erosion by water is similar to licking a sucker. As they lick a sucker, they are “washing away” particles of the sucker. As it rains, the rain washes away particles of the Earth’s surface.
Posted by Kim Angell, Children’s Assistant