Formation of the Wadden Sea

The present Wadden Sea owes its existence to its past.

The period of previous glacial ages (up to 150,000 years ago)

During previous glacial periods, there were times when the region was a shallow sea surrounded by England, Belgium, the Netherlands, Germany, Denmark and Norway. This region, which stretched far into the continent, was covered by ice during the next to last glacial period, weighing down the bottom. The sea level was so low that even the ice-free parts of the North Sea lay exposed. When the glaciers melted, the bottom began to rise while the North Sea filled again with water. A mild and gentle climate followed. The sea rose to a level even higher than today. Sand and gravel, left behind by the glaciers, were now transported by the currents and deposited along the shallow coast.

The currents were influenced by obstacles - remnants from the next to last glacial period. These were moraines and layers of boulder clay, which were so compact that they were not readily pushed around. Parts of Texel and Sylt are examples. After the glaciers melted, large boulders were also left behind, now known as the Texel Stones and the Borkum Reef Grounds. These obstacles influenced the current and were determining factors for the formation of the coast.

The period following the last glaciations (since 15,000 years ago)

During the last glaciation, the water was once again captured in the glaciers, but this time they didn't reach further than northern Germany and Denmark. The adjacent part of the North Sea lay dry. The dominating westerly winds blew large amounts of sand in the direction of the Dutch, German and Danish coasts. Around 10,000 years ago, the temperature began to rise and the ice began to melt. Meltwater from the north and swollen rivers from the mainland hammered against the dry coast, which then consisted of a virtually continuous barrier of sand bars. Large marshes lay behind this sand bar. The barrier broke into pieces due to long-shore currents, expanding and extending the channels.

There were periods of higher and lower temperatures, creating moments of much plant growth, followed by major flooding which killed the plants. Eventually peat bogs formed, which were continually covered with fine mud during flooding, upon which new marshes with plants developed. Mud flats and shallows lay seaward of the marshes. These surfaces were cleaved through by channels originating at the mouths of the rivers on the landside and the seawater flowing between the broken sand bar barrier on the seaside. With help from severe storms in the thousands of years that followed, the channels eventually joined together. The Wadden Sea evolved into a true sea. During a major breakthrough around 1000 years ago, the barrier between the Wadden Sea and the Dutch Zuiderzee was broken and the Wadden Sea was permanently separated from the mainland. During this same period, the German Halligen were formed and the Leybucht inlet was significantly enlarged.

Human influence

Man has also played a role in the formation of landscapes in the Wadden Sea. Centuries long, people have lived and worked in this region. Higher and drier parts of the former marsh were raised, forming terps - artificial dwelling hills. Dikes were built where water used to have free reign. Parts of the natural Wadden Sea marshes were embanked and turned into polders. Livestock such as cows and horses now graze these polders. Sometimes, new salt marshes developed on the seaside of the polder dikes, as can be seen along the mainland coast. These marshes often had a helping hand from man and are usually grazed upon, especially in the Dutch part of the Wadden Sea. Channels leading to harbors must remain passable and are dredged when necessary. All of these activities influence the landscape, often by influencing the current whereby sand and mud end up in places where it otherwise should have landed.