All bogs share some common characteristics. All bogs produce peat and accommodate bog vegetation. However, despite these similarities, bogs come in a number of different types. 

Depending on their topographical features, boggy regions can be divided into three peatland complex types.

Raised bogs are common to Southern Finland. The middle part of a raised bog is higher than its edges, which makes water to flow away from the center of the bog. The raised bog receives nutrients only from rainwater, so the central parts of the bog tend to be low in them. 

Aapa fens have high edges and low centers. This makes water and nutrients flow from the edges of the bog towards its center. Aapa fens are common to Northern Finland, where they can cover large areas of land.

Palsa bogs can be found in Northern Lapland. They are peat mounds, and their lowest parts are frozen throughout the year. As the amount of permafrost peat increases, the bog steadily grows higher. Sometimes, the edges of the peat mound can crumble away, making the frozen parts melt. This can cause the whole palsa pog to sink down.

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Peatland complex types

Type	Features	Species	Where?
raised bog	middle part higher than the edges	few species	Southern Finland, e.g. Torronsuo in Tammela.
aapa fens	middle part lower than the edges	rich in species	Northern Finland, e.g. Ilmakkiaapa in Sodankylä.
palsa bog	permafrost peat mound	rich in species	Northern Laplend, e.g. Iitto in Enontekiö.

The Torronsuo bog in Tammela is an example of a raised bog.