
Dried mud with wind-blown stones
'Mud' is a liquid or semi-liquid mixture of water and some combination of soil, silt, and clay. Ancient mud deposits harden over
geological time to form
siltstone or solid, mudrock lutites. When geological deposits of mud are formed in
estuaries the resultant layers are termed '
bay muds'. Mud is similar to
muck, but lacking significant quantities of
humus, and often containing higher proportions of
sand.
Mud can provide a home for numerous types of animals, including varieties of
worms,
frogs,
snails,
clams, and
crayfish. Other animals, such as
pigs and
elephants bathe in mud in order to cool off and protect themselves from the
sun.
Mud, in the
construction industry, refers to wet
plaster,
stucco,
cement or other similar substances. Mud is closely related to
slurry and
sediment.
In the preparation of materials for making
ceramics, the making of liquid mud (called slip) is a stage in the process of refinement of the materials, since larger particles will settle out of the liquid.
Problems with mud

A lorry stuck in mud
Clay soil can pose problems for traffic when moisture is present. A road built upon such soil may become stable over time as the packing of the soil will make it more water-resistant. However, any attempt to grade it can be disastrous, since excess water can then enter the surface and will be worked in by traffic, transforming portions of the road into a mud bog that can trap vehicles. The typical solution in road building is to add layers of crushed stone. The stone particles will interlock and distribute the weight of a vehicle over a larger surface area. Proper drainage is also essential when low spots are encountered by the road, usually requiring the addition of culverts to pass water underneath the elevation of the road.
Buildings constructed upon clay soil must also be properly drained around their perimeter, particularly where a perimeter
foundation (rather than a monolithic slab) is used. As clay will expand and soften when moisture is added, the resultant mud will squeeze out from underneath the foundation, however, in the next dry cycle it will contract, but the clay squeezed out will not return. Over a number of such cycles the foundation can sink in the moisture-cycled locations, possibly causing both wall and foundation cracks. Maintaining a constant moisture level in firm soil is important and can be effected by appropriate landscaping and landscaping maintenance. Where drainage is toward a building a
French drain may be installed to route water around the building.
Mud in pop culture
Mud is used in
mud wrestling, as a form of entertainment. A
mud bath is a medical treatment.
See also
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Muck (soil)
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Mud volcano
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Peloid