Peat dominated wetlands need two primary factors to develop—excess water and excess peat accumulation. A positive water balance is needed to develop bogs and fens. More precipitation, in the form of rain and snow, needs to fall than disappear through evapotranspiration. Evapotranspiration is the loss of water to the atmosphere through the combined forces of evaporation and plant transpiration. In most cases, precipitation is 30 percent to 50 percent more than evapotranspiration. Peatlands require a humid environment year-round, so an even distribution of precipitation throughout the months and relatively low sun intensity is necessary for optimal peatland development. The second requirement is that peat moss is produced and accumulated faster than it decomposes.

Peatlands generally form under two different circumstances. Some open water lake basins gradually fill in from the surface from Sphagnum mosses, reeds, sedges, and grasses growing and dying. The dying vegetation decomposes slowly due to the low oxygen conditions under water and due to the cool environment. These plants continue to grow and gradually move towards the center of the lake creating a quaking bog. The floating surface continues to be colonized by plants and the process is continued. This type of bog is called a quaking bog because when you walk on it, it “quakes” or undulates as you walk on it due to the water underneath it.

The second type of bog formation is called paludification. Paludification is the process by which the bog grows outside of its basin and flows across the terrestrial landscape to form peat on terrestrial areas. The peat continues to accumulate and compress, until it eventually causes a perched water table near the surface of the mineral soil. The peat dominated wetland, continue to grow and evolve from the formerly terrestrial landscape, until a bog exists.