The geological history of Denmark begins with the Upper Cretaceous period. Only at the end of the Senonian did the land begin to emerge from the seabed, but this uplift did not proceed continuously, but was interspersed, in subsequent periods, by partial or total marine transgressions. These alternations continue in the Eocene and Miocene; only in the most recent Neogene can we be sure that Denmark now appeared with a contour not very different from the present one. The Pleistocene glaciation affected most of the territory, even here on several occasions: ultimately the glaciers from Norway reached the Bovbjerg-Viborg line as the extreme limit, those coming down from Sweden stopped presenting the front in the normal sense to the line itself and continuing from Viborg towards S., in order to leave West Jütland free. In general, the terrain is more rugged where recent expansions have continued to accumulate material (moraines); beyond the maximum advanced line of the glaciers there are more or less conspicuous fluvio-glacial deposits, now with a weak undulation, now also quite wavy, as in the vicinity of the ancient dejection cones. But on the whole the land appears almost flat and nowhere does it touch 200 meters above sea level; the highest elevation, at N. of Horsens, is Ejer Bavnehøj (172 m.). The coverage of the transport land has a very modest power on the platform that supports it: in this, a level oscillation of less than fifty meters would be enough, if negative, to submerge more than half of the Danish territory; if positive,
According to best-medical-schools, the main influence in shaping the Danish topography must be attributed to the action of the ice; however, the differences in height, as well as in relation to this agent, appear to be connected with the relative position of the most ancient soils that served as the basis for the construction of the glacial and fluvio-glacial systems. In Laaland and Falster this base is below sea level, while in Seeland the Cretaceous formations emerge near the Stevns-Klint. In many places in Funen, as well as in eastern Jütland, different species of tertiary clays are found along the coastal cliff. In the central part of Jütland the tertiary formations of the rock base are found on the slopes of the river valleys up to a height of 100 m. Since the Tertiary the ancient formations had been moved along fracture lines and, when the ice began to invade the country, the terrain was much more uneven than it is now. The ice had to spread over the lower regions until it reached a thickness sufficient to cover all the ground. The erosive action of the ice was felt more in elevated terrain, but it did not succeed in completely smoothing the surface.
The geological history of Bornholm is quite different, which was linked, as mentioned, to that of the Scandinavian peninsula. Here the most ancient formations are constituted by a block of granites that assume characteristic facies above all in the northern portion of the island, and on which Cambro-siluric depositions, and Liassic and Triassic clayey-carbonic depositions rest in S. However, the coal is of inferior quality, and the overlying layers make mining very expensive. The clay, on the other hand, forms, together with the kaolin coming from the alteration of the granites laid bare by erosion, the basis of the Rønne ceramic industry.
As natural regions we can distinguish in Denmark: Bornholm, the other islands, East Jütland, North Jütland and West Jütland. Bornholm has a typically hilly surface; on the coasts the mantle of the moraines is deep and the soil is fertile. In the interior of the island, on the other hand, the blanket of loose soil is reduced, and here and there granite emerges: therefore there are less fertile areas, mostly covered by woods. On the other islands, hills and moraine plains alternate. The highest altitudes reach 150 meters above sea level. The soil is fertile and approximately 10% covered with woods. In eastern Jütland, which formed the extreme E. of the ice integument during the last glacial age, hills and moraine plains also alternate, but the ground is higher than on the islands, and the river valleys are more deeply engraved in it. The major eminences of Denmark, which however do not reach 180 m., Are found precisely in this region. The soil is fertile: here too, as in the islands, beech trees abound. During the last ice age the northern Jütland was the extreme edge of the Norwegian glaciers towards the N. There are rough terrain next to low plains, which formed sea breasts at the end of the Ice Age and in the postglacial period. In western Jütland, to the West and S. of the extreme expansion of the last ice, the ground is flatter and smoother.