Formation of delta: Extensive deposits of sand and clay formed at the mouth of any river in sea at the site where the river falls into sea are called delta.
The formation of delta is a very interesting natural phenomenon in which negatively charged colloidal particles of river are neutralized and thus coagulated by the positively ions of the salt present in sea.
As it is very expected, the river water contains colloidal particles of sand and clay which are negatively charge.
On the other hand the salty sea water contains a number of positive ions.
When the water of river comes in contact with water of sea, the negative charge present on colloidal clay particles present in river water get neutralized by the positively charged ions present in sea because of which they get coagulated and deposit at the site.
Delta is formed where river meet the sea, due to the process of settling down of colloidal particles.
The ions present in sea water are responsible for coagulation