Mountains without tectonics: explaining the paradox of the Scandinavian highlands

Mountains usually form where tectonic plates collide, their height supported by thick crustal roots. Yet the Scandinavian Mountains rise far from any active boundary - and without such a root. Using high-density seismic data, we imaged the deep structure of Fennoscandia and found that the continental margin is composed of three major Precambrian crustal blocks. Their arrangement influenced the opening of the North Atlantic and created two sharp lithospheric steps beneath the Southern and Northern Scandes. Such steps create conditions for edge-driven convection in the mantle, which in turn can provide dynamic support for the mountains where no mountains should be. These results point to a broader possible mechanism for mountain building at passive continental margins.