Kuivakaivo is a small waterlogged kettle hole on the eastern edge of Nummikangas. At the end of the ice age, about 10,000 years ago, a large iceberg was buried in Nummikangas. Later on it slowly melted away. What remained was a pit about a hundred meters long and 50 meters wide, which reached the groundwater level. This kettle hole soon started to paludify. A mire was born, the area of which is only half a hectare. However, it is one of the thickest mires in the region. The maximum peat thickness of the dry well is 6.7 meters, which is about two meters more than the maximum thickness of Kauhaneva.