Question

1. how can a boulder turn to silt as it moves down a river?

Explanation:

As the boulder travels downstream, three main processes break it down: 1. Abrasion: It collides with other rocks, the riverbed, and riverbanks, chipping off small pieces over time. 2. Attrition: The boulder rubs against other sediment, wearing down its edges and surface into smaller particles. 3. Hydraulic action: Fast-moving river water forces into cracks in the boulder, widening them and splitting off fragments. Gradually, the large boulder is reduced first to smaller rocks, then sand, and finally fine silt particles.

Answer:

A boulder turns to silt as it moves down a river through continuous physical weathering processes: abrasion (collisions with the riverbed, banks, and other rocks), attrition (rubbing against other sediment to wear down into smaller pieces), and hydraulic action (water forcing into cracks to split the rock). Over time, these processes reduce the large boulder incrementally into tiny silt particles.