Þingvallavatn

The Þingvallavatn [' θiŋk ˌ ˌ vatla vahtn̥ ] is a lake in southwest Iceland in the national park Þingvellir. It is located in the municipality of Grímsnes above Grafningur and Bláskógabyggð.

General

It is debatable whether it is the largest lake of the island with its 83.7 km ². The position is made ​​to it by the reservoir Þórisvatn for several years in dispute. The question is also whether the underlying volcanic islands in it are to be attributed with a surface area of ​​at least 0.5 km ² to its surface or not. In addition, the lake is used at its outflow since 1959 by a power station and therefore easily dammed so that the surface can vary.

Its maximum depth is 114 m. In Þingvallavatn live very many fish, namely sticklebacks, four types char, including the Arctic charr ( Salvelinus alpinus ), and trout. The brown trout (Salmo trutta ) is at the top of the food pyramid in the lake and will weigh up to 15 kg.

Volcanism and fracturing

The lake lies in the so-called Þingvellir Trench and is surrounded by four active volcanic systems: Prestahnúkur and Hrafnabjörg the northeast and Hengill and Hrómundartindur in the southwest.

The presumed age of the lake is about 12,000 years. He emerged at the end of the last ice age. He was initially a glacial lake. The glacier denied at the end of the last ice age the flow of water. Finally, the glaciers retreated, the land below the volcano Hengill rose and the lake was deeper.

A significant change occurred about 10,000 years ago, when the east and adjacent to the volcano system of Hrafnabjörg associated shield volcano Skjaldbreiður originated in a single, long eruption. The lava built up not only the shield volcano itself, but poured on through the valleys towards the lake. Another major volcanic eruption coined about 1,000 years later the area: This time it was even closer to the lakeside volcano Hrafnabjörg himself, who spilled his lava into the lake and its drainage disabled the river Sog. The lake water rose as a result of about 12 m. The river, however, buried his bed through the lava and the water surface fell again by about 7 m.

Years ago, about 2,000 of the Hengill volcano erupted and an island was built in the lake which now bears the name Sandey. Today, the lake gets its water mainly from numerous surface and underground sources in the adjacent lava fields.

In addition, he is surrounded by the grave rupture zone of the Mid-Atlantic Ridge, which stretches diagonally from southwest to northeast across Iceland. As a result, one finds in the area a lot smaller and larger columns that are named in Iceland GJA. The largest is the Almannagjá at Þingvellir, but the most impressive rather Hrafnagjá. Also from the lake are such columns, one of which, significantly, at the lowest point.

Historic site

Of very great historical importance was since the time of the Conquest, ie the colonization of Iceland, the area around the lake. At its north shore namely met already from 930 to 1800 at Þingvellir the Legislative Assembly Alþing, one of Europe's oldest parliaments.