Playground Ground Detectives

A Playground Investigation Report

The school grounds crew noticed changes around the playground. Soil collected below the slide, sand piled beside a fence, and cracks widened in stone edging. Fourth graders investigated. Weathering means rock breaks into smaller pieces. Erosion means rock pieces or soil move from one place to another.

To model water flowing beside the slide, the class prepared three trays. Each held the same kind and amount of soil on the same slope. One surface was bare. One had wood chips. One had growing grass. Students slowly poured one liter of water over each tray from the same height for the same amount of time. They collected the soil washed out, let it dry, and measured its mass in grams.

For the sandy corner, an adult tested three trays inside a clear box that kept sand contained. Each tray held the same amount of coarse sand. The surfaces were dry and bare, damp and bare, or dry with gravel on top. A gentle fan blew toward a catcher for two minutes. Its speed, distance, and direction stayed the same. The adult measured the sand that reached each catcher.

To investigate winter cracks, an adult used two similar sandstone samples with cracks one millimeter wide. Both received equal amounts of water each day. One stayed indoors. The other froze overnight and thawed during the day for ten days. The adult handled the frozen sample. Its crack reached three millimeters wide. The indoor sample's crack stayed one millimeter wide. Water takes up more space when it freezes.

Outside, students also watched a root inside an old crack in the stone edging. During spring, the root grew thicker and pressed against both sides. The crack widened from two to four millimeters. Nearby, grass roots formed a tangled mat through the soil.