Burst pipe outside a property

Leak underground
Burst pipe outside a property, what's the cause? If you encounter a burst pipe outside a property.  Depending on the severity of the leak problems like this can often go unnoticed over an extended period.  Extreme cold weather would be the first thought that comes to mind when an outside leak occurs.  Garden taps and other pipework that are exposed to the outside are susceptible to this.  Pipework installed without adequately weather protection risk the possibility of freezing in server cold ...