Moors began to emerge during the last great Ice Age, the Weichselian Glaciation, when the masses of ice were retreating to Scandinavia. Analysis of peat profiles revealed that the climate was considerably milder 10,000 years ago than it is today. Birches, hazelnut, and oak trees grew in the Ore Mountains. About 5,000 years ago, the climate changed again - the mild temperatures went away, the rainfall increased, and broad spruce forests spread across the ridges of the Ore Mountains.
High rainfall, moisture gleaned from fog by the spruces, and low average annual temperatures resulted in the collection of water in depressions in the ground and on level surfaces. Large cushions of peat moss formed that gradually increased in height and contributed to peat formation. The illustration shows how the moor bulged outward in an hourglass shape after many thousands of years. The outer part of the moor running up the slope has a steeper slope and is referred to as a sloped border. This area is often relatively dry and overgrown with dwarf shrubs or trees. The sloped border may be covered by natural runoff streams created when the moor is saturated with water and allows excess water to run off.
The transition between the sloped border and mineral ground is characterized by a wet border where even very small moor waterways can form sometimes. This area is called a lagg. The central moor area is shaped by a hummock-mud bottom complex, meaning water-filled sink holes turn to raised hummocks overgrown with peat moss. Large waterholes are referred to as potholes. Natural Ore Mountain moors grow approximately 0.5 to 1.5 mm each year, meaning the moor will need about 1000 years to achieve a depth of one meter. One of the deepest moors in the Ore Mountains is the Mothhäuser Haide, with a moor core with a depth of 8.4 meters.
If a moor is drained, the water is is removed from the moor. The peat beds dry up, causing shrinking and sagging. When it is dried out, dwarf shrubs and trees move in - the moor becomes forested.