When rock is weathered and transported downstream, this is best seen as an
example of the conservation of

matter

Explanation:

Matter can neither be created nor destroyed. When a rock is weathered, even though it is broken into smaller particles, they all still exist . If these particles, no matter how minuscule, are combined again they would lead to the formation of same rock. Hence conservation of matter is followed here since rock is a type of matter.

uh two lol

that would be called plucking : )

explanation:

''plucking, also referred to as quarrying, is a glacial phenomenon that is responsible for the erosion and transportation of individual pieces of bedrock, especially large "joint blocks". as a glacier moves down a valley, friction causes the basal ice of the glacier to melt and infiltrate joints (cracks) in the bedrock."