Geography of Iceland

Iceland is a large island in the North Atlantic. She lies on the Reykjanesrücken mentioned, the northeastern part of the Mid-Atlantic Ridge and exceeds the only major part of this sea back to sea level.

The island is located just south of the Arctic Circle about 250 km south-east of Greenland. The area of ​​the island is 103,125 km ², of which 100,329 km ² land area, water area 2796 km ².

The highest point of the island is the Hvannadalshnúkur with 2,110 m. The longest rivers are the Þjórsá 230 km, and the Jökulsá Fjöllum 206 km.

• 4.1 Photos and Videos
• 4.2 Scientific contributions 4.2.1 To volcanism
• 4.2.2 The earthquake
• 4.2.3 Glaciology and isostatic compensation
• 4.2.4 Other

Geology

Iceland is geologically one of the most interesting areas of the world, as several geological phenomena occur simultaneously and influencing one another on the island and it offers a unique field of research for plate tectonic volcanic processes.

Plate tectonic

The Mid-Atlantic Ridge

Iceland is relatively young with an age of about 17 to 20 million years ago. This is due to the situation in the Mid-Atlantic Ridge.

Mid-ocean ridge (short: MOR), which also include the Mid-Atlantic Ridge, are places where the ocean floor is renewed regularly. Through convection processes in the asthenosphere creates a divergent force on the ocean floor, as a result he " tears " and the resulting crack filled by nachfließendes magma (so-called "sea -floor spreading "). This results in time an undersea mountain.

This phenomenon was confirmed by magnetic measurements which, revealed in parallel to this on both sides and oriented substantially symmetrical strip ocean floor with alternating polarity emanating from the MOR. This alternately inverse and normal oriented polarity of the ground stems from the phenomenon of pole jump, through which approximately every 500000-750000 years, the polarity of the Earth's magnetic field is reversed. The exact causes that are lead to the pole shift not been explored. The regularly funded the reasons mentioned above basaltic magma contains mineral particles that map on cooling to lavas in their magnetic orientation of the respective magnetic field. If cooled rapidly by the contact of magma with water releases striking shapes such as pillow lava and lava tubes.

For the aforementioned processes follows that the age of the ocean floor decreases with increasing proximity to the MOR. The same chronological and magnetic structure of the soil can also be observed in Iceland, ie Iceland is a part of the Mid-Atlantic Ridge, which represents the boundary of the Eurasian plate with the North American plate. Which occurs in the middle of a MOR crest - or central column (also called " rift " ) is partially visible on Iceland and on land, for example in Þingvellir National Park, where she has created the Almannagjá even a kind of natural amphitheater. The alternating polarity of the soil is partly already detectable with a simple compass. In contrast to Madagascar, for example, a so-called " micro- continent", Iceland is therefore not of continental crustal material, but purely oceanic origin. This is also reflected in the petrological composition of the island rock, mainly composed of basalts. The aufdringenden magmas are mostly mafic to intermediate with a SiO2 content of 40-65 %.

The age of the rocks is divided the history of the Mid-Atlantic Ridge, following from west to east:

The area of ​​the western and northwestern part of the island consists of tertiary basalt formations and is mostly older than 3 million years. An exception is Snæfellsnes, where the volcanic activity 7 million years ago only stopped, but then started again 2 million years ago. The last eruptions took place in this area for land acquisition time to 900 instead ( in Hnappadalur ). There are still 3 active volcanic systems.

They are followed east with about 700000-3 million years altpleistozänen rocks of the extinct volcanic zone. The rocks of the volcanically active Mid-Atlantic Ridge are younger than 700,000 years, and constantly renew itself. East of the volcanically active zone is the eastern part of the extinct volcanic zone, also called "gray basalt formation". Subsequently, there is again a tertiary education, but to a lesser extent than in the west of the island.

Due to the constant volcanic activity due to the spreading tendencies of the Mid-Atlantic Ridge Iceland grows to about 2 cm per year in the east-west direction. However, growth in the west is much stronger than that facing east.

The Iceland Plume

Main article: Iceland plume

In fact, there are few islands that are part of the 15,000 km long mid-Atlantic ridge: the Azores, the islands of St. Peter and St. Paul, Ascension, and Tristan da Cunha, Gough and Bouvet Island and the north of Iceland Jan Mayen. However, Iceland is the area terms by far the largest collection of MOR world. This exceptional position Islands (also: Manteldiapir ) by the Iceland plume so-called explained. This is a particularly strong and hot convection currents in the asthenosphere beneath the island. Its origin is probably due to the Earth's core and the boundary between Earth's mantle at about 2880 km depth. However, it has been around much longer than Iceland, it is assumed that the plume originated in the late Paleocene under Greenland during the opening of the North Atlantic about 60 million years ago. This coat - diapir into the region around Iceland by its emerging forces in raising the surrounding ocean floor and thus to a survey of the island above sea level. Moreover, it is a result of the hotter stream, and greater magma to increased volcanic activity, which promotes or accelerates the growth of the island. This is confirmed by Geoidanomalien, located in the center of Iceland: The region around the island rises about 70 meters above the geodetic reference ellipsoid.

An alternative, controversial theory explains the anomaly by the presence of a larger amount of eclogite in the upper mantle, the more melt produced at a given temperature than the main mantle rock peridotite.

Seismic activity

Because of the steady growth of the island in the east and west and resulting tensions it comes to numerous earthquakes. While there are a large number of so-called micro- earthquakes ( on the Reykjanes peninsula in southwest Iceland up to two dozen a day), very large earthquakes are less common. The strongest quake previously identified in Iceland occurred on August 14, 1784 in the southwest of the island and had a magnitude of 8.0 on the Richter scale. This mountain slopes came into the slides and new geysers created. About 500 farms were destroyed or heavily damaged.

It is striking that the epicenters of earthquakes are mainly found in the southwestern and northern parts of the island. This accumulation is explained by transform faults and strike-slip faults of the Mid-Atlantic Ridge that are located in these areas. These are caused by shear dislocations of the MOR, ie a shift of parts of the MOR, which usually divide the back vertically against the strike. Such zones are known to be seismically active regions and are not very common.

Volcanism

Iceland is one of the most active volcanic areas in the world and therefore has a rich volcanic geomorphology. This is partly due to the situation in the Mid-Atlantic Ridge, on the other hand at the Iceland plume, which is located under Iceland.

Active volcano zone

The active volcanic zone of Iceland is concentrated along the course of the plate boundary and the central column of the Mid-Atlantic Ridge, since swells fresh magma. Active volcanoes are located in a few tens of kilometers wide neovulkanischen zone ( with the exception of the volcanoes on Snæfellsnes ), which is in the southern half of two branches, in the northern half of a strip. All three zones converge in the area of Vatnajökull. The ancient basalt fields in the west and east of the island due to the tertiary volcanism. The growth Islands in the East-West direction, the existing there volcanoes were gradually cut off from the central column of the MOR and inactive due to the lack of Magma promotion. The same applies to the Grey Basalt Formation of the inactive volcanic zone of the Altpleistozäns. The oldest basalts of the Pleistocene are the tertiary yet very similar. However, they contain more sediment, Palagonite and moränenartige deposits ( tillites ), which document the glacial activity in Iceland.

The most active volcanoes are located in uninhabited Icelandic highlands. Areas where you can observe the volcanic activity particularly well, eg Landmannalaugar are in the south or the Krafla caldera in the north of the island. Many of the volcanoes have glaciated peaks, the following ( with the glacier surfaces):

• Vatnajökull ( 8100 km ²)
• Langjökull ( 953 km ²)
• Hofsjökull (930 km ²)
• Mýrdalsjökull ( 595 km ²)
• Drangajökull (199 km ²)
• Eyjafjallajökull (107 km ²)

Upstream of the island are more volcanic islands ( Heimaey, Surtsey, and others).

The last volcanic eruptions have taken place so far in 2000 ( Hekla ), 2004 ( Grímsvötn ), 2010 ( Eyjafjallajökull ) and 2011 ( Grimsvotn ).

In the lava fields, many caves are located both in the Blocklavafeldern and in the Fladenlavafeldern, called in Icelandic Hellishraun to the German Höhlenlava, but this has no scientific meaning.

Pillow lavas, shield volcanoes and mesas

During the ice ages, when several hundred meter thick glacier Iceland buried among themselves, a special form of volcanism trained. It usually came to effusive promotion of magma, which was melted by the heat of the glaciers in the exit region of the magma. Due to the high pressure of the ice and the rapid cooling by the water led to the formation of pillow lava ( pillow lava ). The resulting Pillowrücken can now be seen for example on Sigalda in southern Iceland. Be continued the magma promotion, the pressure decreased gradually, and there was a so-called Palagonittuff due to ash eruptions. Broke through the volcanic glacier, due to Effusivförderung a shield volcano above the ice. Shield volcanoes promote low-viscosity lavas, which are spread over a large area. Therefore shield volcanoes have a slope of only about 8 ° (eg Kjalhraun ). Broke through the lava to ice sheets of the glacier, then basalt plateau formed. After melting of the glacier then remained a so-called panel volcano with its characteristic steep walls back (eg Herðubreið ).

Columns eruptions and crater rows

In Iceland, however, many other volcanic types are represented. Commonly include the columns eruptions. Here, along a up to several kilometers long column of magma is ejected. This happened for example in the 30 km long volcanic fissure Eldgjá in 930

Gradually, the ejection activity mostly concentrated in certain places. Here, form small cones that form in the wake whole chains of volcanoes, so-called crater rows, such as the Lakispalte in southern Iceland, where over a length of about 25 km was a crater chain with over a hundred chimneys in 1783.

Other types of volcano

Strato volcanoes exist on Iceland only in very small numbers. They promote large amounts of rhyolitic ash and have a typical conical shape (eg Snæfellsjökul ).

The Hekla volcano has a unique shape and is a hybrid between a column and a volcano stratovolcano.

Also Tuffringe can be found on Iceland. They were created by a single volcanic event, a phreatomagmatic explosion that occurred in the lava in contact with water. The most famous example of this is the Kraterart Hverfjall of Lake Mývatn.

The Icelandic so-called Eldborgir (Fire Castle ) are welding cinder cones, sometimes individually, as the Eldborg í Hnappadal, but also often stand in rows along with cinder cones on a volcanic fissure, as in the volcanic mountain range of Bláfjöll in Reykjavík in the craters of the Veiðivötn or the Laki craters.

Geysers

Another phenomenon of volcanic activity in Iceland are the geysers and hot springs. In Iceland, there are about 600 larger hot springs.

Spring springs, the geysers are called (Icelandic: geysa - swirling, flow ), arise when they have a relatively narrow channel eruption. By Magma been heated seepage of the water column in the eruption channel to well over 100 ° C is heated due to the pressure. Individual bubbles to rise and squeeze some of the water out. Thus, the pressure drops and the superheated water turns abruptly into water vapor. The following eruption may be up well over a hundred meters throw the water into the air. However, such high outbreaks are rare. Geysers usually do not exist for a long time, since the eruption channel by landslides or earthquakes can be easily spilled or is broadened by the eruptive behavior of the channel and, therefore, sufficient pressure can no longer be established. The geyser is then added to a hot spring. On the other hand, they are often created by earthquake activity and emergence of new columns. The most famous geysers of Iceland are the Strokkur Geyser and Grand Geyser.

The influence of the water

Glacier

Iceland is repeatedly named the island of fire and ice. Not without reason, because in addition to the 33 active volcanic systems, there are various forms of water and not least the glaciers of the island, which have influenced this.

Cold and warm periods

The glaciers of the Ice Age rested until 10,000 years ago in Iceland. However, there was also there already considerable climate variability, so that the glacier stretched during cold periods, the warm periods have melted, however.

During cold periods, the whole country was covered with layers of ice that were up to 2,000 m thick.

From in front of about 10,000 to 2,500 years ago the climate was then quite mild, warmer than at present, and the ice melted.

But then it was pretty fast becoming colder and created today's domestic Seiss Childe as the Vatnajökull.

During the colonization of the land in the 9th and 10th centuries it was again slightly warmer than today.

Then there was again a cold period from the 13th to the late 19th century, which is now known as the Little Ice Age.

Glacial erosion

The glaciers are always moving. They walk and run forward and she constantly scrape on rocks among themselves. They erode mountains in this way and created such as the U-shaped valleys in the area of Akureyri or Kare in the walls of the Westfjords.

Also, the valleys narrow lakes such as the Skorradalsvatn and the fjords were formed by the glaciers.

The fjords are always towards country Affairs deeper, because here the glacier rested longer and heavier and therefore could affect its erosive power stronger.

Current Situation

Currently, about 8 % of the country mostly covered with glaciers, the surface shrinks as everywhere in the world due to the greenhouse effect. For example, the largest Icelandic glacier Vatnajökull lost more than 10 % of its volume in the last 100 years. It is suspected that this might have stronger volcanic activity resulted because the ice cover on the volcanoes is thinner and the country lift, with new columns and openings arise, can climb through the magma. Similar phenomena are from the end of the Ice Age - known - in Iceland, about 10,000 years ago.

The rivers have shaped Iceland, because they erode through the power of flowing and rushing water the earth.

This manifests itself as the Gullfoss waterfalls, the downright eaten them up in columns that were created by the tectonic movements, and it has expanded and deepened considerably.

There are three basic types in the rivers: the source fluxes, the water level is more or less uniformly high, as in the Hvítá in Borgarfjorður; the glacial rivers like the Skeiðará whose water levels is subject to very large fluctuations, especially in summer, but also due to volcanic influences; the collection rivers that receive especially the water of other streams and rivers, and especially during the thaw may swell strongly, such as Norðurá in Borgarfjorður.

Particularly strong erosive power have the glacial rivers. So the Skeiðará transported in the known glacier run 1996, huge amounts of debris with it and moved the coastline into the sea. Rivers carry so not only, they also build on.

Sea

The North Atlantic around Iceland has a tremendous force. Waves can pile up to 20 meters off the southern coast.

So you can watch about Dyrhólaey how the rocks of the cape from year to year gnawed and more ground from the sea. The sea has shaped coastlines in the mountains: in the south of the country one sees everywhere former Cape. The river deposits but have then moved the coastline later in the opposite direction.

But the sea grows not only from, but on. Good observe this can be illustrated by the many peninsulas Eyri mentioned in the Westfjords. There sandbanks were stranded on which today are a variety of places such as Þingeyri or Flateyri.

Wind erosion in Iceland

The location of the island of Iceland in the North Atlantic due to special climatic conditions. This means that the country is also influenced specifically by storms and was.

You fight against this permanent soil erosion, the storm can be so strong that he even pops up the asphalt on the roads literally or ground into small particles, sweeps away.

Especially in areas where the soil and vegetation are already attacked by overgrazing or influence of water and volcanism anyway, the winds have easy game. They contributed and contribute to the desert-like appearance of large swathes of land, especially in the interior of the island with.

You can see that about when the island from north to south crossing on one of the mountain tracks as the sprengisandur, but also on the ring road in the highlands at Möðrudalur.

Most important is the wind erosion on sandy plains, where the glacial rivers such as the Skeiðará, the Kúðafljót or Jökulsá Fjöllum always supply deposits. In prolonged dry periods may therefore occur on the Mýrdalssandur or in the desert Möðrudalsöræfi eg to sandstorms. The sand is sometimes carried it hundreds of miles through the air and can be about the Borgarfjorður (West Iceland ) suddenly contribute to quite hazy air.

However, wind erosion can also help especially Palagonitfelsen quite interesting shapes as you can see, for example, in the Þórsmörk.

Dunes there in Iceland hardly at most beaches.

A striking feature of wind erosion and thus the destruction of fertile land in Iceland called Rofaborð ( Isl rof " erosion ", rofaborð " erosion table "). Here the wind as you also know it at German coastal landscapes around in dunes on Sylt has made already fragile already due to other influences soil erosion advantage, and this eroded further. The result is as pissed -looking bump that still bears some grass just at the top.