Vertical movements

Because the mantle is inaccessible for direct observations, processes in the mantle are numerically determined. Parts of the crust can be studied directly at the earth's surface, and observations can be made on properties such as structure, density, chemistry and age of geological units, as well as on the topography and bathymetry of today´s surface. In the subsurface, seismic data may provide information on the structure and stratigraphy of previously subsided basin areas. Researchers at NGU´s Bedrock and Crustal processes team address these issues and provide data and interpretations in a range of fields.

Thermochronology

Thermochronology, the study of the temperature history of rock samples, can yield valuable information on vertical movements and their expression at the surface. Combinations of tectonic uplift and erosion at the surface will eventually result in exposure of geological units that were previously at greater depth and therefore at higher temperatures.

The cooling history of a rock therefore relates directly to its path from (deep) within the crust (or upper mantle) to the surface. Once at the surface, the rock becomes part of the erosional template, and susceptible to transport and deposition in sedimentary basins. Faults at all scales (lithosperic to upper crustal) play a critical role in vertical movements, and some of the most spectacular examples in the world crop out in Norway.

Rocks that were subducted into the mantle 400-425 million years ago beneath the Caledonian mountain belt are now exposed at the surface in western Norway. Their exposure was assisted by an impressive array of normal faults and shear zones with displacements in the order of many tens of kilometres. Similar structures were active in the formation of Norway´s continental margin in the Mesozoic, when the foundation was laid for Norway´s oil and gas reserves. Normal faults with less displacement, but a more recent movement history, appear to have played an important role in the shaping of Scandinavian topography, including the present-day landscape. Erosional surfaces incised into the bedrock are recognised today as uplifted, undulating landscapes that pre-date the last glaciations. The uplift and modification of these landscapes appears to have been assisted by faults on a range of scales.  The products of prolonged fault activity in Norway affect everyday life in a variety of ways, from tunnel construction to landslide distribution. 

Interaction between the mantel and lithosphere

On the continental and global scale, a proper understanding of mantle and lithosphere dynamics is critical. Dynamic topography is the part of topography that is caused by density anomalies and flow in the mantle, which combined with processes in crust and lithosphere determine which parts of the earth's surface are exposed above or submerged below sea level  at what times. Researchers at NGU's Center for Geodynamics work with better constraining density structure and rheology (i.e., how deformation occurs under stress) in the Earth's mantle and lithosphere, and with improving numerical models to compute resulting deformation and topography.