Scientists solve mystery of why Scandinavian mountains stay high without deep roots
Researchers have overturned a century-old geological assumption about how mountains stay aloft. The Scandes mountains in northern Scandinavia are buoyed by dense rock far below the crust, not by the thickened crustal roots scientists expected. This finding reshapes understanding of passive continental margins—crucial for oil and gas exploration, mineral deposits, and infrastructure planning across stable coastlines worldwide.
Originaltitel: Northern Scandinavian mountains supported by a low-grade eclogitic crustal keel
<p>Plate tectonics predicts that mountain ranges form by tectono-magmatic processes at plate boundaries, but high topography is often observed along passive margins far from any plate boundary. The high topography of the Scandes range at the Atlantic coast of Fennoscandia is traditionally assumed isostatically supported by variation in crustal density and thickness. Here we demonstrate, by our Silverroad seismic profile, that the constantly ∼44 km thick crust instead is homogenous above the Moho, and Pn-velocity abruptly change from 7.6 km s<sup>-1</sup> below the Scandes to >8.2 km s<sup>-1</sup> below the Proterozoic shield. By modelling gravity anomalies and topography, based on the seismic model, we demonstrate that this change corresponds to an increase in metamorphic eclogitic grade from 35% below the high-topography Scandes to 70% below the low-topography shield. The sharp contrast between the low-grade, reduced-density and the high-grade, high-density eclogitic bodies below the uniform seismological Moho explains the enigmatic topography of the mountain range without a crustal root.</p>