Why does a fast-moving river carry larger rocks than a slow-moving river?
AFast rivers are deeper, so there is more room for big rocks
BFast-moving water has more energy, so it can lift and carry heavier particles that slower water would leave behind
CFast rivers have special chemicals that dissolve large rocks
DBig rocks only exist near fast rivers
The speed (velocity) of water determines its carrying power. Faster water has more kinetic energy, enabling it to lift larger and heavier particles from the riverbed. When a river slows down (at a bend, in a wide section, or where it enters a lake or ocean), it drops the heaviest sediment first because it no longer has enough energy to carry it.
Question 2 Short Answer
How did the Grand Canyon form?
Think about your answer, then reveal below.
Model answer: The Colorado River gradually carved the Grand Canyon over approximately 5-6 million years. The river eroded downward through layer after layer of rock as the Colorado Plateau was slowly uplifted by tectonic forces. The result exposed nearly 2 billion years of rock layers.
The Grand Canyon demonstrates the incredible power of water erosion over long time periods. The river did not do it alone — weathering weakened the canyon walls, and gravity caused rockfalls that widened the canyon. But the primary cutting force was the river's persistent downward erosion.
Question 3 True / False
Rivers primarily erode the land during major floods.
TTrue
FFalse
Answer: False
Rivers erode constantly — every day, flowing water is picking up and carrying sediment. However, erosion rates increase dramatically during floods because the water is deeper, faster, and has much more energy. A single major flood can do more erosion in a few days than normal flow does in years. But normal, everyday flow is responsible for the majority of long-term erosion.