Bedrock . The Caledonian
nappes are shown in green. Note the
windows of bedrock belonging to the
Transscandinavian Igneous Belt in blue. The
Svecofennian and
Sveconorwegian provinces are shown in yellow and salmon respectively. approximately 390 million years ago. The red line shows where the
Iapetus Suture extends in the present day. Note that
Scandinavian Caledonides were just one branch of the Caledonian orogeny that affected much of what is now Europe. Most of the rocks of the Scandinavian Mountains are Caledonian, which means they were put in place by the
Caledonian orogeny. Caledonian rocks overlie rocks of the much older
Svecokarelian and
Sveconorwegian provinces. The Caledonian rocks actually form large
nappes () that have been
thrust over the older rocks. Much of the Caledonian rocks have been eroded since they were put in place, meaning that they were once thicker and more contiguous. It is also implied from the erosion that the nappes of Caledonian rock once reached further east than they do today. The erosion has left remaining massifs of Caledonian rocks and
windows of
Precambrian rock. While there are some disagreements, geologists generally recognize four
units among the nappes: an uppermost, an upper, a middle and a lower unit. The lower unit is made up
Ediacaran (
Vendian),
Cambrian,
Ordovician and
Silurian-aged
sedimentary rocks. Pieces of Precambrian
shield rocks are in some places also incorporated into the lower nappes. Geologically, the Scandinavian Mountains are an elevated,
passive continental margin similar to the mountains and plateaux found on the opposite side of the
North Atlantic in
Eastern Greenland or in Australia's
Great Dividing Range. A two-stage
model of uplift has been proposed for the Scandinavian Mountains in South Norway. A first stage in the
Mesozoic and a second stage starting from the
Oligocene. In South Norway, the Scandinavian Mountains had their main uplift phase later (
Neogene) than in northern Scandinavia which had its main phase of uplift in the
Paleogene. The various episodes of uplift of the Scandinavian Mountains were similar in orientation and tilted land surfaces to the east while allowing
rivers to incise the landscape. Some of the tilted surfaces constitute the
Muddus plains landscape of
northern Sweden. The progressive tilt contributed to create the parallel
drainage pattern of northern Sweden. Therefore, the common labelling of the southern Scandinavian Mountains and the northern Scandinavian Mountains as two domes is misleading. Various mechanisms of uplift have, however, been proposed over the years. A 2012 study argues that the Scandinavian Mountains and other elevated passive continental margins most likely share the same mechanism of uplift and that this mechanism is related to far-field stresses in Earth's
lithosphere. The Scandinavian Mountains can according to this view be likened to a giant
anticlinal lithospheric
fold. Folding could have been caused by horizontal compression acting on a thin to thick crust transition zone (as are all passive margins). Alternative lines of research have stressed the
role of climate in inducing erosion that
induces an isostatic compensation;
Quaternary geology Many slopes and valleys are straight because they follow tectonic
fractures that are more prone to erosion. There is evidence that the
drainage divide between the
Norwegian Sea and the south-east flowing rivers were once further west. It is estimated that during 50% of the last 2.75 million years the Scandinavian Mountains hosted mountain-centered
ice caps and
ice fields. The ice fields from which the
Fennoscandian Ice Sheet grew out multiple times most likely resembled today's ice fields in
Andean Patagonia. As the ice sheet retreated to the Scandinavian Mountains it was dissimilar to the early mountain glaciation that gave origin to the ice sheet as the
ice divide lagged behind as the ice mass concentrated in the west. ==Highest mountains==