Mud Day 2011, Westland, Michigan, United States

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. Humans have also used mud as a building material, or a sealant material.
Problems
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 street.