Why a delta is formed at the point where rivers enters the sea. Give explanations with reference to surface chemistry coagulation of colloidal particles.
Answers
A delta is formed at the meeting point of sea water and river water. ... Those clay particles float very well in fresh water, but the salt in sea water causes them to coagulate and stick together and sink to the bottom
Deltas are formed at the end of rivers (river mouth) as it flows into the sea. Rivers carry a lot of sediment (mud). The river flows into a calm sea. This slows the river down. Which makes the river drop its sediment. This deposited sediment builds up over years creating a delta.
River flowing towards oceans contains slits and sand which on collision with salty sea water, electrolytes neutralise a charge on coloidal particles and result in the prepration of sand , clay etc
And thus due to huge amount of production of silt and sand results in the formation of delta.
When river enters an ocean~
Suddenly the force of the water current slows down as it enters the sea. With that slowdown, the sediment slows or stops moving, so it is just dumped at the mouth of the river. The ocean currents will start moving some of it along the coast and spread it out, but if the river is carrying much sediment it will overwhelm the ability of the ocean currents to move the sediment away.
When "dirty" water in the river (water that has clay particles suspended in it) hits the ocean it mixes with salty sea water. Those clay particles float very well in fresh water, but the salt in sea water causes them to coagulate and stick together and sink to the bottom. You can do an experiment yourself to show this: mix some dirt into sink water and stir it up. It will stay muddy. If you dissolve some salt in a cup of water and then mix the salty water with the muddy water the mud will settle out and the water will clear up.