Table of the geological timescale of the Pleistocene and Holocene with a summary of the most important sedimentation processes in this period in the Netherlands.
Like in the other parts of the Netherlands, the soil at the surface of Nijmegen and surroundings consists mainly of 'young sedimentation material from abroad' deposited during the last 2.5 million years. Clay, sand and boulders have been transported as erosion products from the old mountains, like the Ardennes and the Eifel, but moreover from the younger Alps (arosen about 100 to 50 million years ago during the Cretaceous and Tertiary; see Geological time table) by precipitation and melting water with the Rhine, Meuse and Scheldt to the lower basin of the Northsea. Where now the Netherlands are located, a large plain of fluvial sedimentation material has been formed under influence of always shifting meanders of rivers. During Pleistocene, the oldest period during the Quartery epoch, about 2 million years ago, a number of glacial episodes have come and gone repeatedly. The determining factor for the growth of ice sheets is precipitation as snow in winter but moreover relatively low temperatures in summer so that a part of the snow remains and thus a nett accumulation of snow or ice occurs. The concensus is that several factors may cause such temperature decrease: changes in atmospheric composition (among which the CO2-concentration), variation in the earth' orbit with respect to the sun (excentricity; B), variations in angle of rotation axis of the earth relative to itsorbit around the sun (obliquity; C) and variation in precession (D) (the Milankovitch cycles; watch a video lecture by Dr. Pearson), variations in activity of the sun, movements of tectonic plates and changes in sea streams, impacts of large meteorites and exceptional vulcanic eruptions.
Milankovitch parameters. It is assumed that variations in these parameters (B-D) contribute tot climate changes, in particular to the occurance of glaciations. A. Seasonal variations, B. Excentricity of the earth' orbit, C. Oblicity and D. Precession
Part 1 and part 2 of the film "Understanding the Earth" (in English; produced by TV Ontario and Laurentian University in collaboration with Dr. David Pearson) about the formation of ice sheets in North-America, the end moraine deposits and the formation of glacial tills.
Most important for the morphogenesis of the landscape around Nijmegen are the last two glacial ages, the Saalian glaciation (380 000 to 128 000 years ago*), and the Weichsel glaciation ( about 116 000 to 12 000 years ago*), as well as the interglacial Eemian (about 128 000 to 116 000 years ago*). The Holocene, the period after the last Ice Age, from about 12 000 year ago on, includes the era in which man has had a large impact on the landscape, also in Nijmegen: first on a local scale, like in the Roman time in which an army camp Noviomagus was settled, and furtheron from the industrial revolution on moreand more intensively, leading to urbanization.
Saalian glaciation: continental ice sheets, glacial tills and drought
The glacial Saalian, about 200 000 to 125 000 years ago, was named after the Saale, a side river of the Elbe. Other local names for this cold period are the Riss glacial in Mid-Europe (the Alpine area), the Wolstonian on the British Islands, the Moskovian or 'Dnieper valley in Russia amd the Illinoian in Northern America. During the Saalian glacial ages (map of Saalian in the Netherlands) the Scandinavian gletscher ice has spread over a large part of Northern Europe, in the Netherlands up to about the line Haarlem-Nijmegen.
The slowly progressing heavy ice mass scrapped the meters-high frozen upperlayer over the relatively soft soaked and not frozen sunderlayer. During this process enormous scales of soil were pressed aside or forward and tilted to ridges (see below a scheme in Dutch on how these glacial tills were formed). This is how glacial tills or push moraines, called "stuwwal" in Dutch, arose in the regions Gooi, Utrecht Hills, Veluwe, Veluwe Rim, the area of Holterberg and Montferland, and also along the traject Nijmegen-Kleef (Link to the geomorphological map of the Netherlands showing the location of glacial tills).
During the Saalian the temperature was over a long period in the average several degrees lower that the present average. Yet, the normal winter-summer fluctuations and relative temperature shifts over periods of decades or hundreds of years also occurred during such a glacial period.
The huge amount of water in the states of ice and snow (The evaluated increase in ice was 15 to 44 x 106 km2 and the volume from 27 to 77 x 106 km3), caused a dramatic decrease in the quantity of water available for the geo-atmospheric cycle. Therefore the climate became drier and the sea level dropped with more than 100 meter, so that the south part of the Northsea became ground. Various sediments among which very fine one, which previously belonged to the sea bottom, became exposed to the air surface. In the Saalian the course of the Rhine, which had a much reduced debit, was deviated southwest by the ice mass and the glacial tills. The Rhine streamed through the present Niers valley and downstream from Gennep westwards together with the Meuse up to the northern part of the present Doggersbanks in the reduced Northsea. The Meuse, like the Scheldt and the Thames, had become an affluent of the Rhine (map of the rivers during the Saalian).
Regarding the vegetation, the area south of the ice sheets concords best with a tundra, with hardly any trees. A kind of permafrost will have existed, but in the warmer years, the upper level of the soil will have thawed, and will have been washed away by the melt water over the surface of the frozen underlayer.
End of the Saalian - Eemian: Sandr and breakthroughs in the glacial tills
At the end of the Saalian and during the transition to the warmer (interglacial) Eemian the ice tongues melted rapidly. The efflux by the rivers of melting water with sediments from the ice sheets and the glacial tills (fluvio-glacial sediments) raised tremendously. As a consequence at the south(west) side of the glacial till a kind of alluvial fan consisting of boulders, sand and loam particles, so-called Sandr plain (see figure here above). The most coarse debris sedimented closest to the glacial till, while finer particles, the smaller and lighter they were, were carried further away by the meltwater before sedimenting.
The Niers valley and the entire Rhine/Meuse valley could not absorb the huge quantity of meltwater anymore. The water of the Rhine raised against the glacial tills situated south-east of Nijmegen, giving rise to a number (four?) of breakthroughs at places where the glacial tills was low. This is the reason while the Rhine nowadays streams (again) north of the Nijmegen glacial tills, but south of the glacial tills of Montferland and the Veluwe. The natural resource "De Gelderse Poort" which abounds in water, thus thanks its origin to these local disruptions of the glacial tills (more information on nature and recreation around Nijmegen).
During the more humid and warm Eemian the formation of a river plain has continued; the process of sedimentation by Meuse, scheldt and Rhine proceeded, while the Northsea regained its earlier size due to the global raise in sea level. Thanks to the higher temperature a more or less united forestrial vegetation could be restored in these regions.
Weichselian: cold, drought and effect of the wind
The Weichselian glaciation (50.000-10.000 years ago, named after the river Weichsel (=Wisla), corresponds to the Würm in the Alpine sequence, the Devensian Stage in the British Isles, Midlandian in Ireland, the Wisconsin Stage in North America and Pinedale glaciation in the Rocky mountains. In the Weichsel the Scandinavian ice sheet hardly reached the Netherlands, so that no new glacial tills were formed around Nijmegen. However, a repeat was observed of some of the above described conditions characteristic for the glacial era: the Northsea was again partly dry, and the fine sediments of loam particles became exposed. Due tot the cold climate a protective cover of vegetation lacked; at the most a tundra-like vegetation grew.
At that time the (prepoundarily west) winds could carry away much of the fine sedimental material from the southern Northsea basin and deposit it at the lee of the glacial till. This is why nowadays löss depositions are found at the north-east side of the Nijmegen glacial till. Of course, such eolic (wind) deposition also occurred during the Saalian, but those sediments are not found back in the current Nijmegen region, because the fine löss material was dropped on the ice. The löss in the PorvinceLimburg, however, has been deposited in the earlier dry Saalian period, as well as the black earth in the Ukraine and further on in Russia.
Impact of man
Excavations revealing hunting of mammoths have brought to the light that there was human activity in the areal corresponding to the Netherlands since the last glacial era. In the area called nowadays "Land over de Waal" (around Lent, Bemmel, Oosterhout, Nijmegen Waalsprong), 7000 years-old remnants of settlements dating from the stone age have been found by archeologists (article, in Dutch)in the soil. However, it is only with the arrival of the Romans that the impact of man on the landscape becomes evident. The great historian Tacitus described the landscape in the North of the country as "an area from which one can not say whether it belongs to the land or to the sea". But already then, people lived there there, who built even mounds to shelter for high water levels. At that time, the drier part of the country and the elevations of the glacial tills were covered by oak-beech forests (Querco-Fagetum). The wet river clay north of Nijmegen (the Betuwe) was covered with forests of alders (Alnetum).
Excavation of a Roman army camp at the Kops Plateau in Nijmegen
Source : Omroep Nijmegen 1992 (YouTube), Duration 5:11, Dutch
The Roman have clearly marked the landscape, especially in the higher places in the Nijmegen region. One can think of the undercome for the soldiers in large camps (castra), like on the Nijmegen till at the locations called Kops plateau en Hunnerberg (Romeinse castella = fortification, between the "Berg en Dalseweg" and the steep slope of the moraine till). The Romans digged canals and moved river beds in order to get better access the entire region. Examples are the "Drususgracht", a connection between Rhine and IJssel, and in the west of Holland the Vliet. Interessing is that pollen diagrams of borings on the steep north side of the Kops plateau, the Roman camp, demonstrated that the Romans have cut down the woods from the year 10 BC on; pollen of certain tree species disappear from the layers dating that time on. In younger strati of these samples pollen of various grass species and plants resistant to trampling were found, and in a later stage also from cereals (more about Pollen and Biology). After the year 70 AC the Romans leav the Kops plateau, after which the woods slowy recover their position, as appears from the increase of pollen from forestrial species. Also after leaving service some legionairs began tolay terrasses and to construct farm complexes (villa's) in the warmest and most fertile places in the moraine tills. For building houses they used loam from the glacial tills (like probably where the present playing area "Leemkuil" is situated) to bake stones and roofing tiles (see maps of the Roman settlements).
From the Middle-Ages on man's influence on the area becomes even more important. At various places water-powered mills are built and mill basins are digged to collect the water from the hills. The terrasses agriculture on the most fertile area expands. In the early Middle-Ages the first dikes are laid by connecting river banks together. After closing the bandijk (the main river dike) in the senteenth century some curves in the Waal are even straighted up, like near Gendt that was thread by the meandering Waal.