Big idea: wind, water, and ice change the shape of the land

Rocks and Erosion: How Land Changes Shape Grade 4

Why some rocks scratch and some fizz, how a trickle of water carves a canyon, what keeps a hillside in place, and how a boulder ends up as sand. Four hands-on lessons on rocks, weathering and erosion.

• Can water carve a canyon? 50–60 min

  Students build a stream table in a foil pan of damp sand, let a steady trickle of 'rain' run down a gentle slope and a steep one, and measure the channel each time. They use the measurements to explain how running water carves valleys and canyons and drops sand where it slows down.

• What protects a hillside from washing away? 55–60 min

  Teams build model hillsides of soil in foil pans, some bare, some covered with leaves or mulch and some held together with string 'roots', then make it rain on each one the same way. They measure the runoff and the mud it carries, and recommend the best way to protect a real slope.

• How do rocks become sand? 50–60 min, plus a 5 min check the next day

  Students shake sugar cubes in a jar for set times and measure how their sharp corners wear into rounded grains, then watch frozen water push a plug out of a sealed straw. They explain how tumbling and ice break rock into smaller and smaller pieces, all the way down to sand.