Answer:
gravity
Explanation:
streams erode dirt and rocks, transport the sediment, and redeposit it in new locations shaping the earths surface into a system of stream valleys. streams now flow downhill due to the force of gravity
Cold air IS less dense, sinks, holds less vapor
The river had been called <span>"river of sorrows" due to its constant flooding during its earlier civilizations. </span>
Great plains is the broad interior are of north america that used to be grasslands