In the erosion runoff activity, what measurement do students collect to quantify erosion?

• A. Dry mass of sediment in runoff
• B. Volume of water runoff
• C. pH of runoff
• D. Color of sediment

Answer: (A)

Measuring erosion is about how much soil is moved, not just how much water runs off. The dry mass of sediment in runoff gives a direct, mass-based estimate of soil loss: you collect the runoff, dry the sediment to remove the water, and weigh it. Drying ensures you’re counting actual soil, not water weight, so the result is a consistent measure of how much soil was carried away.

If you only looked at the volume of water, you’d learn about water flow, not how much soil moved. pH tells you chemical properties, not quantity of soil loss, and color is only a qualitative cue, not a precise amount. So the dry mass of sediment in runoff is the most accurate way to quantify erosion in this activity.