About 65% of Dawson City has permafrost underneath. Permafrost is perpetually frozen ground all year long. When the settlers moved into the area, they built houses with stoves. The heat from the stoves radiated into the ground below causing the permafrost to start melting and turn into a muddy slush. As it melted, houses began to shift and sink. It is the reason they don't pave any of the roads here because the asphalt insulates and heats the ground.