Mud season occurs in places where the ground freezes in winter and thaws in spring. Dirt roads and paths become muddy because the deeply frozen ground thaws from the surface down as the air temperature warms above
freezing. The frozen lower layers of ground prevent water from
percolating into the soil so the surface layers of soil become saturated with water. Clay-based soil, especially when combined with poor drainage, is especially prone to forming deep and sticky mud. In sandy soils, the top unfrozen layer becomes waterlogged during thaws, but does not form viscous mud. On the
Great Plains, a particular type of clay (
bentonite clay, or
aluminum phyllosilicate) turns into a sticky form of soil called
gumbo during snowmelt and spring rains. Mud season can be expensive for towns due to the damage done to dirt roads. One report concluded that the cost of re-engineering dirt roads so that they would remain passable during mud season in the state of
Vermont could run as high as . Transportation problems during mud season have military implications, due to the bogging down of horses and military equipment in deep mud. During mud season, soil becomes fragile and care must be exercised in protected and recreational areas.
"Breakup" "Breakup" originally referred to the "breaking up" of river and lake ice. This event is eagerly anticipated in many
regions of Canada, because it marks when different
modes of transportation can be used. Vehicles from
dog sleds to
snowmobiles and even
tractor trailers can safely traverse
ice roads in the winter and
aircraft with skis for landing gear can land on ice in winter, but not near breakup. By contrast after breakup, various boats can once again use the water. The exact date this occurs varies across the North, and corresponds to different seasons in the
indigenous calendars of different regions. In the
Cree and
Ojibwe calendars, one of the six seasons is called
minoskamin (
Woods Cree: ,
mithoskamin;
Atikamekw:
miroskamin, etc.) which is usually translated as "breakup". For the
Woods Cree of Northern Saskatchewan this occurred in roughly May and June on the English calendar before the effects of
recent climate change. By contrast the New England mud season of (or "unlocking" as
Kurt Vonnegut called it) is in March and April. Famously, the exact date of the breakup on the
Yukon River in
Dawson City has been the subject of
gambling since the
Klondike Gold Rush, providing climate researchers with a rare unbroken record of climate data in such a remote region. The sense of "breakup" was later expanded to the time of the year when the frozen soil that can support heavy vehicles softens. This is especially used in the
oil patch (which is concentrated on the Great Plains and western portions of the
boreal forest of Canada (i.e. the
Western Canadian Sedimentary Basin) when well drilling activity halts and
work camps "break up" for the spring. ==Around the world==