bringing with them sand and gravel on their journey to the sea. The large amounts of sand and gravel settled as thick, smooth, westward-sloping blankets between the 'hill islands', turning the landscape into a flat plain.
The islands emerge
The ice retreated again and the sea started to rise. Around 8,000 years ago, the water had risen so much that the sea had become what we know today as the North Sea. Since this time, the tidal waters, the wind and the waves have formed the landscape. The North Sea moved the sand from the large meltwater rivers back towards the coast, where it settled as sand flats. However, over time the sand flats reached a height at which they were only flooded occasionally and, thus, the characteristic Wadden Sea landscape - the highsands - were formed. The islands were invaded by plants that could trap the drifting sand between their stems and, thus, the first sand hills were born, and thereby the Wadden Sea islands.
Animals and plants
During high tide, around 2 km3 of water washes through the Danish Wadden Sea. The water brings large amounts of sand and clay into the lagoons between the islands and the mainland where a small amount is deposited in the calm environment.