Windstorms that cause tree uprooting on particularly unsteady soils as well as periodic strong runoffs contribute to create or maintain a local hummock-hollow topography.
Floodplain and swamp ecosystems are inherently seasonal, and many of them feature microtopographic hummock-hollow variation.
In the peat-swamp forest, the microtopography was characterized by the distribution of small hummocks on the waterlogged forest floor.
Vegetation moulds can be seen on the underside of some of these hummocks.
Swamps tend to fill themselves in naturally and unevenly with hummocks; raised fields can be interpreted as enhanced hummocks.
They prefer mildly acidic soils, growing in woods near pines or hemlock or mossy hummocks.
Trapped between the freezing surface soils and the buried permafrost layer the soil material is forced upwards into hummocks.
Often the larvae settle so close together that hummocks are formed as the juvenile barnacles grow.
