Why are the deposits of streams graded with the largest boulders or pebbles at the bottom?
A)The largest boulders are always at the bottom; they never move.
B)The largest boulders eroded from the stream bank immediately roll to the bottom and stay there.
C)Jostling of boulders, pebbles, and sand in turbulent water moves the boulders to the bottom.
D)As the water slows after a flood, the largest boulders drop out first.
E)Tributaries add additional sediment to the stream.

Question

Quizplus · Accepted Answer

The largest boulders drop out first as the water slows down after a flood, due to their greater mass and the decreased ability of slower-moving water to carry heavy particles. This process is known as graded bedding or size sorting, where sediment is deposited in layers with the coarsest material at the bottom, gradually transitioning to finer material at the top.

Why Are the Deposits of Streams Graded with the Largest