The Mississippi River carries more silt than any other river does. Standing on the delta, the river slowly deposits some of this silt in the salty marshes. Thirty tons of silt arrive each second. When thoroughly laden, you can see the river choke the marshes with mud.
As the muddy delta grows, the river seeks a new path to the Gulf of Mexico often. The Mississippi has had seven deltas during the past five thousand years. The delta, therefore, is a collection basin for silt that is always changing.