Silt is the fine bits of clay and sand that become sediment settling at the bottom of a river or lake. If there's a lot of silt flowing in a river, it looks murky.
Silt is the super-fine dirt that you might see at the bottom of a lake or river. When your feet touch silt it feels slimy, and once it’s stirred it up the water looks muddy. Where the Mississippi River enters the Gulf of Mexico, a lot of silt has been deposited and over time has built up a portion of land called the Mississippi Delta. The region surrounding this accumulation of silt is home to music called the Delta Blues.