The peat layer in a raised bog consists mainly of peat mosses, which can grow several centimetres per year. They are then compressed by their own weight and become peat in the absence of air due to the ideally high water level. This peat layer can grow by about 1 mm per year in mid-latitudes.

Literature: https://www.nabu.de/natur-und-landschaft/moore/deutschland/index.html, https://www.dbu.de/umweltpreis-blog/der-umweltpreis-geht-an-die-moore/