How do rocks get distributed in and along lakes and rivers? What causes weathering and erosion to create different size rocks? Objective Students will sort rocks in various ways from a river gravel bar (adapted from FOSS). Background The most common earth material is rock . Rock that has broken away from the continuous layer of bedrock is found in particles of many sizes. Weathering (sunlight, chemical, frost action) breaks rock loose and erosion (moving water, glaciers, landslides) moves it to another place. Currents of water can sort particles by size. These particles are classified (largest Duration: 60 Minutes Additional Standards: NGSS 4-ESS2-1. Make observations and/or measurements to provide evidence of the effects of weathering or the rate of erosion by water, ice, wind, or vegetation. Essential Question How do rocks get distributed in and along lakes and rivers? What causes weathering and .