Answer to Question #63716 in Other Physics for Afroz
Moon raise tides on the sea but why not it raise tides on the river?
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.