Answer to Question #63716 in Physics for Afroz

Question

Moon raise tides on the sea but why not it raise tides on the river?

Answer 1

Tides form because the gravitaty of the Moon moves large amounts of water in seas and oceans. Rivers have relatively small width, thus the effect is not significant. However, a tidal phenomenon called Pororoca is observed in Amazonia. When the tide is high, water flows in from the Atlantic ocean into Amazon river. As a result, Amazon's flow reverses.