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Frisian Islands Chain and Dikes in the Netherlands

May 13th, 2009 Category: Snapshots

The Netherlands - May 12th, 2009

The Netherlands - May 12th, 2009

The West Frisian Islands, in a chain off the coast of the Netherlands, separate the North Sea from the Wadden Sea, an intertidal zone between the continental coast and the islands.

While the North Sea is deeper and appears dark navy blue here, the Wadden Sea has a greenish brown color, as it is a shallow body of water with tidal flats and wetlands rich in biological diversity.

The biggest and most populated of the Frisian Islands is called Texel. It is also the westernmost of this archipelago, and forms the largest natural barrier between the two seas. The dune landscape on Texel is a unique habitat for wildlife.

Below Texel and the Wadden Sea is a body of water formerly known as the  Zuiderzee. After being closed off from the North Sea by a dike, it was separated into two lakes: the IJsselmeer and the Markermeer, which are in turn separated by another dike called the Houtribdijk.

These dikes are visible in the full image as lines where the color of the water changes abruptly from dark brown (Wadden Sea), to dark green (IJsselmeer) to bright green (Markermeer).

The West Frisian Islands and the Houtribdijk, Holland – February 2nd, 2009

February 2nd, 2009 Category: Image of the day

Holland (The Netherlands) - January 30th, 2009

Holland (The Netherlands) - January 30th, 2009

The West Frisian Islands are a chain of islands in the North Sea off the Dutch coast. The islands visible here belong to Holland (the Netherlands); however, the chain continues further east as the German East Frisian Islands.

From west to east the islands are: Noorderhaaks, Texel, Vlieland, Richel, Griend, Terschelling, Ameland, Rif, Engelsmanplaat and Schiermonnikoog. The ones obscured by clouds, continuing to the East, are:  Simonszand, Rottumerplaat, Rottumeroog and Zuiderduintjes.

The Frisian Islands are nowadays mostly famous as a holiday destination. Ferries allow tourists and residents to move from island to island.

Below the islands is what was formerly known as the Zuiderzee, a shallow inlet of the North Sea in the northwest of the Netherlands.

In the 20th century, however, the majority of the Zuiderzee was closed off from the North Sea (leaving the mouth of the inlet to become part of the Wadden Sea) and the salt water inlet changed into a fresh water lake called the IJsselmeer.

The water in the inlet contains a dark green algal bloom that appears more intense in the souther section. This is because the lower part is actually a shallow lake called the Markermeer.

The Markermeer and the IJsselmeer are separated by a dike called the Houtribdijk. It is 30 kilometers long and connects the cities of Lelystad and Enkhuizen. The structure itself is not visible in the image, but it’s precise location can be identified as the line where the algae changes from bright green to dark greenish-black.