Vättern By Sentinel-2

Vättern ( , ) is the second largest lake by surface area in Sweden, after Vänern, and the sixth largest lake in Europe. It is a long, finger-shaped body of fresh water in south central Sweden, to the southeast of Vänern, pointing at the tip of Scandinavia. Being a deep lake at or below sea level at its deepest point, Vättern is about 1/3 the surface area of Vänern but in spite of this contains roughly 1/2 of its water.

Vättern drains into Motala ström through Bråviken into the Baltic Sea, but also has a downstream connection since 1832 through Göta Canal to Vänern and the Kattegat tributary of the Atlantic Ocean. The lake has plenty of sources from rivers and small lakes, with the highest located sources being near Nässjö on the South Swedish Highland near the southeastern shoreline.

Name

The name Vättern is closely related to "vatten", the Swedish word for water, and also means "water, lake".

Geography

The lake's total surface area is about , with a drainage basin a little over double that, about . The deepest known point, located to the south of the island of Visingsö, is . The average depth is . The lake has a perimeter of about . The volume is . These numbers tend to be fixed, as the level of the lake is regulated.

Situated in Götaland, the lake is drained by Motala ström, starting at Motala, and flowing ultimately through a controlled canal into the Baltic Sea. The lake includes the scenic island of Visingsö, located outside Gränna. Other towns on the lake include Vadstena, Jönköping, Hjo, Askersund, Åmmeberg and Karlsborg. It is bounded by the Provinces of Västergötland, Närke, Östergötland and Småland.

In the north there is a scenic but not mountainous inland fjord, Alsen. About 62% of the drainage basin is still covered with spruce, pine and deciduous forest. About 26.7% is dedicated to agriculture.

Geology

While many of smaller lakes in southern Sweden are thought to have originated by glacial stripping of an irregular weathering mantle in the last 2.5 million years Vättern formed by tectonics as a graben 700 to 800 million years ago in the Neoproterozoic. Granitic basement rocks in the lake are deformed ( foliated) by the Protogine Zone that crosses the area. The basin is partially filled by sedimentary rock of the Visingsö Group of Neoproterozoic age. This group include rocks such as conglomerate, sandstone, arkose and carbonates. The older of these sediments deposited before the Vättern came into existence as a graben. Acritarch microfossils such as '' Chuaria circularis'' are common in Visingsö Group.

During the most recent millions of years multiple glaciations have covered the lake and its surroundings, leaving glacial striations and drumlins as they receded.

The present-day lake began as an independent body of water left by the receding Scandinavian glacier after the last glacial period around 10,000 BP. It became a minor bay of the Baltic ice lake. Most of the lake's relict species (like the Arctic char) date from that time. Subsequently, it was a bay of Yoldia Sea and then became connected to Ancylus Lake, discharging from the north end of its extent. At about 8000 BP an accident of the uneven Scandinavian isostatic land rise brought Vättern above Ancylus and the two became distinct.

The annual post-glacial rebound today is in northeastern Motala and in southern Jönköping. This means that Vättern is tilting to the south by every year.

Biology

The lake contains both phytoplankton and zooplankton, such as Copepoda and Cladocera. The benthos

HOME


Content is Copyleft
Website design, code, and AI is Copyrighted (c) 2014-2017 by Stephen Payne


Consider donating to Wikimedia



As an Amazon Associate I earn from qualifying purchases