Þjórsárdalur

The Þjórsádalur is a valley in the south of Iceland.

Name and river

The valley is grazed by Iceland 's longest river Þjórsá, from where the name originates.

Position and shape

The Þjórsárdalur is the easternmost valley in the canton Árnessýsla. It is located north of the mountain Gaukshöfði between the small mountains Hagafjall and Búrfell ( Þjórsá ).

A large part of the valley is a barren sandy desert, which is due to the frequent eruptions of the nearby volcano Hekla.

However, the State Forestry Association ( Skógrækt ríkisins ) has endeavored to reforestation and soil fixing since the 30s. This can be seen as the Skriðufell. In addition to the planting of trees also lupins and oats were sown beach.

Volcanism

Hekla

In the Middle Ages the valley was relatively densely populated. However, the sat an enormous explosive eruption of Hekla in 1104 to an end. The 20 then buried under ash courtyards were excavated partially in 1939, including the museum's courtyard Stöng whose reconstruction Þjóðveldisbær now resides near the power plant Búrfellsstöð.

Traces of an even more powerful eruption of Hekla can also be found in the Valley: The whitish rhyolitic ash Plinian Eruption of these, which took place about 2,900 years ago, you can still find on the mountain slopes of the surrounding area and on mountain Skeljafjall the layer is about 2, 5 m thick.

Bárðarbunga

In addition to the Hekla volcano, other systems have influenced the shape of the valley. This is especially true for the system of Bárðarbunga, which has sent on the transactions in the Icelandic highlands crater rows of Vatnaöldur and Veiðivötn lavas down to the lowlands.

First of all here is the Búrfellslaven the speech that flowed 3,500 years ago from the Tungnaá basin and inter alia cover the bottom of the valley. These lavas also formed, as they ran down wet moorlands, the pseudo craters located in Talinneren.

The lavas flowed through a small canyon called Gjáin in the Þjórsárdalur.

Cooled off central volcano

For example, below the waterfall Háifoss recognize the remains of an old central volcano, which has grown cold. Therefore, there is also rhyolite in the vicinity of the waterfall.

The Þjórsárdalur was virtually cut into the volcano, which has been given subsequently the name of the valley. Strictly speaking, it is geologically in the valley to the remains of a caldera of about 8 km in diameter, as can be seen especially nice when mountain Fossalda, where many courses have dug in older rhyolite and Andesitgestein. This conveyor paths ( Dykes ) connect the magma chamber with small Rhyolithlavadomen.

In the valley you will find next to tillite rocks and pillow lava and Andesittuffe. This in turn suggests that, when the volcano in front of about 2 million years ago was still active at the same time a glacier filled the caldera.

Various Basaltlavaströme from other sources buried the remains of the volcano first, to the glaciers of the Ice Age, these eroded and partially brought him to light.

The eponymous Þjórsá touches the valley actually only on its south side. In the valley itself, however, there are four rivers: Fossá í Þjórsárdal that forms the beautiful waterfalls Háifoss and Hjálparfoss and RAUDA Sandá and Grjótá.

Power plant Búrfellsstöð

The large hydroelectric power plant Búrfellsstöð was put into operation in 1972. It is below the Samstaðamúli. There you will find the turbine house and near a small village located there the employees and workers has emerged. For them, a swimming pool in the desert was built in Reykholt in Þjórsádalur, which is still in operation.