Mechanical perturbation
It consists of the destruction of the features of illuviation formerly considered (mainly coatings). The illuvial clay accumulations do not remain undisturbed in the soil and the causes of their modification are many.
Mechanical perturbation
In clay soils, the changes in humidity cause expansions and contractions which severely deform the illuvial accumulations.
On other occasions, it is the neoformation of pedological compounds, as in the case of carbonate precipitation, that causes the fragmentation and disorganisation of the clay coatings.
Biological perturbation
The biotic activity is also an important cause of perturbation.
Cryoclastial perturbation
Finally, cryoclastia can affect the conservation of illuvial accumulations in cold climates.