How the deep levels of the Earth affect the surface topography of the globe

Relief is not just a matter of bark. The coat underneath also has its own word. It is especially capable of influencing the relief, creating uplifts or, conversely, basins, the amplitude of which can reach two kilometers.

Mountains, basins, plains… The relief that marks our landscape is the result of the movements of tectonic plates, causing massesmasses continental, but also processes of erosion and alteration that level peaks and move sediment particles. Therefore, we are inclined to believe that topography is influenced only by the evolution of the earth’s crust, that is, the shell solidsolid the farthest part of the globe. However, we forget that coatcoat what’s underneath also plays a role.

The effect of the mantle hidden in the relief of the earth’s crust

The influence, of course, is more subtle and noticeable only on large wavelengthswavelengths. Thanks to geodetic and gravimetric studies, we know that surface topography is the result of the sum of several components. Thus, there is a crustal component based on local crustal thickness and isostasy (i.e. the effect of the crust floating above the mantle), and a mantle component based on. anomaliesanomalies thermal underwear coat. This component of the mantle is difficult to notice at first glance. It appears only when the crustal component is subtracted from the topography. Thus, in some cases we can observe the appearance of “residual topography” associated with the influence of the mantle.

Topographic changes up to 2 km.

A new study has just revealed this residual topography on a global scale based on an analysis of 26,725 points measuring the thickness of the Earth’s crust. The results were published in the journal Journal of Geophysical Research: Solid Earth show that while this mantle influence is often visible at the level of plate boundaries, it is also present within plates, where it can cause topographic changes on the order of two kilometers (highs or troughs) and which can extend for hundreds or hundreds of kilometers. even thousands of kilometers. This residual topography is associated with changes in temperature as well as chemical structure within the mantle. A warm anomaly in the mantle will lead to uplift, a cold anomaly will lead to subsidence of the earth’s crust. These new results may provide a better understanding of some geological processes, in particular the presence of magmatism in these regions, away from plate edges.