Geology of the Netherlands
The oldest stones that you can find at the surface of the earth originate from the Carboniferous period. This era started 355 million years ago and ended about 290 million years ago. Stones from this era can be found in the Heimans Quarry, near to the village of Epen. In the north and south of the Netherlands, this layer of stone lies four kilometers below the earth’s surface. Due to erosion however, this stratum of stones has since disappeared. The layer on top of the Carboniferous layer is about 250 million years old (the Permian era). Near Slochteren, this layer consists of sandstone. Slochteren is known for its natural gas reserves, located at a depth of 2.8 kilometers. During the Permian, in the north of the Netherlands large quantities of rock salt were produced.
The era Trias followed the Permian. Some stones that were formed are: sandstone, evaporite (sediments that were created through of evaporation of water), chalk, dolomite, shale and gypsum. Shale disappeared almost everywhere because of erosion. By the end of Trias (about 200 million years ago), a sedimentation process started which would last for approximately 20 million years. During the Jurassic period (200 – 160 million years ago) rocks that may contain petroleum were formed. This is why the ground under the North sea contains so much petroleum.
Later, in the Cretaceous period, the sea played an important role in the development of the Dutch landscape. The meteorite that hit the Mexican peninsula Yucatan 65 million years ago, meant the end of the dinosaurs. Another consequence of the impact was an increase in the average sea temperature by 10 degrees Celsius. In some parts of Europe, the average sea temperature was at that time a comfortable 25 degrees Celsius – much warmer than the North sea is nowadays during the summer.
During the Cretaceous period, the Netherlands was completely covered with water. The chalk that was deposited during that time, is used today as building material, mortar, fuel and fertilizer. During the last period of the Cretaceous, the old layers were disturbed. In the northern part of the Netherlands, the Cretaceous layer is locally 1.5 kilometers thick.
The sediments of the Mesozoic were later covered with younger sediments. Clay layers that originate from the Oligocene (40 – 24 million years old) are mined in quarries and used to produce bricks. In the following era, the Miocene (24 – 5 million years ago), quartz and brown coal were formed in the south-eastern part of the Netherlands. The Pliocene was the transitional stage between the Miocene and the Pleistocene, which started 1.8 million years ago. The clay and sand sediments that can be found in the surroundings of the city of Breda were formed during the Pliocene. In the Pliocene, the rocks that were transported by the rivers Rhine and Meuse dominated the scenery. During the ice ages the advancing ice changed the rivers’ course.
The first time that ice covered the Netherlands was during the Elsterien period, and the second time was during the Saalien period. During the Saalien, the Dutch landscape was radically changed: lateral moraine and boulder clay were deposited. Enormous boulders were also transported into the Netherlands. Between 2700 and 2400 B.C. these stones were used to build megalithic tombs. After the second ice age, the sea gradually withdrew. Loam and peat sediments originate from the period after the Netherlands' ice ages. A third ice age, the Weichselien, never reached the Dutch border. However, strong cold winds shifted large quantities of sand around the country.
Throughout the last 10,000 years, the geological development of the Netherlands has largely been determined by a rise in sea level, which was about 65 centimetres for each century. In the coastal areas, a constant battle between land and sea has been taking place. The area just behind the the coastal area developed rapidly. The sea level rose, and rose and rose even more. 8000 years ago, it reached a level that is 20 meters below the level it is today. Different kinds of (‘old’ and ‘young’) seaclay was moved onto already existing layers of peat. Dunes have only developed within the last 3,000 years. The vast peat areas in the provinces of Drenthe and Groningen also originate from the Holocene.