Mud is a mixture of water and some combination of soil, silt, and clay. Ancient mud deposits harden over
geological time to form sedimentary rock such as shale or mudstone (generally called lutites). When geological deposits of mud are formed in estuaries the resultant layers are termed bay muds. Mud is closely related to slurry and sediment.
Mud that is mostly clay, or a mixture of clay and sand may be used for ceramics, of which one form is the common fired brick, or dried with the inclusion of straw reinforcing to form an unfired adobe brick. Adobe walls are frequently finished with a mud plaster, seen at right. Such buildings must be protected from groundwater, usually by building upon a masonry, fired brick, rock or rubble foundation, and also from wind-driven rain in damp climates, usually by deep roof overhangs. In extremely dry climates a well drained flat roof may be protected with a well-prepared and properly maintained dried mud coating, viable as the mud will expand when moistened and so become more water resistant.
Providing a habitat for animals[]
Mud can provide a home for numerous types of animals, including varieties of worms, frogs, snails, clams, and crayfish. Also microorganisms can make a home in mud. Other animals, such as pigs and elephants, bathe in mud in order to cool off and protect themselves from the sun. Humans have also used mud as a building material, or a sealant material.