The study of tectonics treats the changes in form of rocks, i.e. rock deformation. This subject has a linking function among the various Earth Science fields (Sedimentology, Petrology, Geophysics, Rock Mechanics, etc.) and permits conclusions concerning the formation of the mountains based on regional rock distribution and the internal structure of the single geological units.
The beginning of all tectonic work is the summary and presentation of all available discontinuity planes, folds and other distortions in and between the individual rock and tectonic units (molasse, flysch, imbricate zones (imbricate zones, nappes, etc.). This is carried out using field mapping (including the summary of the spatial position of the rocks using a geologist's compass), the spatial analysis of borehole data as well as through geophysical and microtectonic investigations.
The summary of structural geological data can be presented in the form of maps, cross-sections, 3D models and diagrams. Detailed structural geological descriptions and models are of critical importance for construction projects in rock (tunnels, caverns, quarries, mines, among others) and for the evaluation of natural risk (rockfall, rock slides and landslides).
Two basically different deformational behaviour patterns can be observed. Rocks with brittle behaviour rupture by overstress (applied stresses in excess of the rock's strength) and fractures and slip surfaces are formed. Earthquakes can also occur along with these processes. This behaviour occurs for most rocks at temperatures under 300-400 °C. At higher temperatures and greater depth other completely different mechanisms are observed. The rock begins to «creep» and to «flow» (ductile, plastic deformations) and is no longer deformed along single surfaces, but inside larger zones. While brittle deformations prevail in the Jura mountains, numerous zones in the Pennine layers show signs of plastic deformation.
The deformation and movement of the rock units can be traced back to globally acting forces which had their beginning in plate tectonics. These brought about repeated far-reaching extensions and compressions of the Earth's crust. During the formation of the Alps, the original Tethys marine deposits, originally located side by side, were compressed together, folded and pushed over each other as nappes.