Mývatn
Encyclopedia
Mývatn is a shallow eutrophic lake
situated in an area of active volcanism in the north of Iceland
, not far from Krafla
volcano
. The lake and its surrounding wetlands have an exceptionally rich fauna of waterbirds, especially duck
s. The lake was created by a large basalt
ic lava eruption 2300 years ago, and the surrounding landscape is dominated by volcanic landforms, including lava pillars
and rootless vents (pseudocrater
s). The effluent river Laxá is known for its rich fishing for Brown Trout
and Atlantic Salmon
.
The name of the lake (Icelandic
mý ("midge
") and vatn ("lake"); the lake of midges) comes from the huge numbers of flies
(midges) to be found there in the summer.
The name Mývatn is sometimes used not only for the lake but the whole surrounding inhabited area. The River Laxá, Lake Mývatn and the surrounding wetlands are protected as a nature reserve (The Mývatn-Laxá Nature Conservation Area).
Since the year 2000, a marathon around the lake takes place in summer.
-rich springwater and has a high abundance of aquatic insects (Chironomidae
) and Cladocera
that form an attractive food supply for ducks. Thirteen species of ducks nest here. The duck species composition is unique in the mixture of Eurasian and North American elements and of boreal
and arctic
species. Most of the ducks are migratory, arriving in late April - early May from north-western Europe. The most abundant is the Tufted Duck
, which immigrated to Iceland at the end of the 19th century. The Greater Scaup
is the second most common duck species.
Other common species include the Barrow's Goldeneye
, Red-breasted Merganser
, Wigeon
, Gadwall
, Mallard
, Common Scoter
, Long-tailed duck
and Teal
. The outflowing Laxá river has a dense colony of Harlequin Duck
s and there is a large colony of Eider
s at the river mouth some 50 km away from Lake Mývatn. The Barrow's Goldeneye is special in being the only nearctic
duck in the area (and Iceland as a whole). Its population of about 2000 birds relies entirely on the habitat provided by the Mývatn-Laxá water system and its surrounding lava fields. Most of the Barrow's Goldeneyes overwinter there, using ice-free areas kept open by emerging spring water (both warm and cold) and in the strong river current. This species is a hole-nester, in North America using tree-holes, but at Mývatn the birds use cavities in the lava for nesting. The other duck species nest abundantly in the numerous islands of the lake and the surrounding marshlands. There is a long tradition of harvesting duck eggs for home use on the local farms. To ensure sustainability, the harvesting follows strict age-old rules of leaving at least four eggs in a nest for the duck to incubate.
Other common waterbirds include the Slavonian Grebe
, Red-necked Phalarope
, Great Northern Diver
, Red-throated Diver
and Whooper Swan
.
The waterbird situation has been monitored annually since 1975 by the Mývatn Research Station.
Lake Mývatn was created about 2300 years ago by a large fissure eruption pouring out basaltic lava. The lava flowed down the Laxárdalur Valley to the lowland plain of Aðaldalur where it entered the Arctic Ocean
about 50 km away from Mývatn. The Crater Row that was formed on top of the eruptive fissure is called Þrengslaborgir (or Lúdentarborgir) and has often been used as a textbook example of this type of volcanic activity. There was a large lake in the area at the time, a precursor of the present-day Mývatn. When the glowing lava encountered the lake some of the water-logged lake sediment
was trapped underneath it. The ensuing steam explosions tore the lava into small pieces which were thrown up into the air, together with some of the lake.
By repeated explosions in a number of locations, groups of craters built up and now dominate the landscape on the shore of Lake Mývatn and also form some of the islands in the lake. This type of lava formation is known as pseudocrater
s or rootless vents. A group of such craters at Skútustaðir on the south shore of the lake is protected as a natural monument and is frequented by tourists. Other pseudocrater groups in this lava field are in the Laxárdalur Valley and Aðaldalur. The formation of pseudocraters halted the advance of the lava in some places creating temporal lava lakes. The lava eventually drained from the lakes, leaving behind a forest of rock pillars. The biggest of these formations is named Dimmuborgir
. At another place, Höfði, the pillars stand in the lake water. The lava created by the Þrengslaborgir eruption is known as the Younger Laxá Lava.
The Mývatn district lies on the western border of the volcanic zone which cuts across north-eastern Iceland from north to south and is an extension of the Mid-Atlantic Ridge
. All geological formations are quite recent, dating from the Ice Age
and postglacial times.
The bedrock
of the moors west of Lake Mývatn is made up of interglacial
lava flows. Most of the mountains in the vicinity of the lake were formed by eruptions under the ice sheet in the glacial periods of the Ice Age. Eruptions that melted their way up through the ice formed table mountain
s (Mounts Bláfjall, Sellandafjall, Búrfell, Gæsafjöll), those which didn't formed hyaloclastite
ridges (Mounts Vindbelgjarfjall, Námafjall, Dalfjall, Hvannfell).
At the close of the Ice Age, about 10,000 years ago, the Mývatn basin was covered by a glacier which pushed up huge end moraines which can still be seen at the north end of the lake. After the glacier started melting, a glacial lake
was dammed up in the Mývatn depression until the glacier retreated from the present course of Laxá river.
Postglacial volcanism in the Mývatn district may be divided into three cycles. The Lúdent cycle commenced shortly after the close of the Ice Age. The explosion crater (tephra
ring) Lúdent dates from this cycle. Its eruption was followed by a number of small fissure eruptions. About 3800 years ago the shield volcano
Ketildyngja was formed about 25 km south-east of Mývatn, and from it a huge lava flow, the Older Laxá-lava, spread over the southern part of the district, plunged down the Laxárdalur valley and flowed almost to the sea. This lava dammed up the first Mývatn, which was about as large as the present lake.
The second volcanic cycle, the Hverfjall cycle, began 2500 years ago with a gigantic but brief eruption, which formed the explosion crater (tephra ring ) Hverfjall
(also named Hverfell). An eruption in Jardbadshólar followed, producing the lavafield between Reykjahlíð and Vogar. Approximately 200 years later a vast lava flow, the Younger Laxá-lava, was erupted (see above). The lava dammed up the present Lake Mývatn and also the lakes Sandvatn, Grænavatn and Arnarvatn.
The third volcanic cycle began with the Mývatnseldar eruptions in 1724-1729 which commenced with an explosion that formed the crater lake
Víti. Later lava flowed from Leirhnjúkur down to the north end of Lake Mývatn, destroying two farms. The Mývatnseldar eruptions are quite similar in character to the recent volcanic activity near Krafla in 1975-1984. The source of both is a central volcano lying between Krafla and Gæsafjöll. Inside the volcano resides a magma chamber
from which molten magma
periodically bursts into a swarm of fissures that cut through the volcano from north to south.
The recent activity was characterized by periods of slow land rise, interspersed by shorter periods of rapid subsidence, underground magma bursts, rifting, earthquake
s and eruptions (nine in all). This is an excellent example of the process of continental drift
in Iceland. A central volcano and its associated fissure swarm is called a volcanic system. The Krafla volcanic system is one of several such systems which together form the volcanic zone of Iceland.
A few rhyolite
mountains border the Krafla central volcano (Mounts Hlíðarfjall, Jörundur, Hrafntinnuhryggur).
Because of the volcanic origin, there are silica quarries in the lake.
, also known as Cladophora ball, Lake ball, or Moss Balls in English, a species of filamentous green algae (Chlorophyta).
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
situated in an area of active volcanism in the north of Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
, not far from Krafla
Krafla
Krafla is a caldera of about 10 km in diameter with a 90 km long fissure zone, in the north of Iceland in the Mývatn region. Its highest peak reaches up to 818 m and it is 2 km in depth. There have been 29 reported eruptions in recorded history....
volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
. The lake and its surrounding wetlands have an exceptionally rich fauna of waterbirds, especially duck
Duck
Duck is the common name for a large number of species in the Anatidae family of birds, which also includes swans and geese. The ducks are divided among several subfamilies in the Anatidae family; they do not represent a monophyletic group but a form taxon, since swans and geese are not considered...
s. The lake was created by a large basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
ic lava eruption 2300 years ago, and the surrounding landscape is dominated by volcanic landforms, including lava pillars
Lava pillars
Lava pillars are common within collapsed sheet flow terrain. Lava pillars are hollow inside forming a pipe-like channel between the bottom and the top of a lava flow. They sometimes coalesce to form walls or can be attached to other pillars by natural bridges....
and rootless vents (pseudocrater
Pseudocrater
A pseudocrater is a volcanic landform which resembles a true volcanic crater, but differs in that it is not an actual vent from which lava has erupted...
s). The effluent river Laxá is known for its rich fishing for Brown Trout
Brown trout
The brown trout and the sea trout are fish of the same species....
and Atlantic Salmon
Atlantic salmon
The Atlantic salmon is a species of fish in the family Salmonidae, which is found in the northern Atlantic Ocean and in rivers that flow into the north Atlantic and the north Pacific....
.
The name of the lake (Icelandic
Icelandic language
Icelandic is a North Germanic language, the main language of Iceland. Its closest relative is Faroese.Icelandic is an Indo-European language belonging to the North Germanic or Nordic branch of the Germanic languages. Historically, it was the westernmost of the Indo-European languages prior to the...
mý ("midge
Midge (insect)
Midges comprise many kinds of very small two-winged flies found world-wide. The term does not encapsulate a well-defined taxonomic group, but includes animals in several families of Nematoceran Diptera. While some midges are vectors for disease, many others play useful roles as prey items for...
") and vatn ("lake"); the lake of midges) comes from the huge numbers of flies
Fly
True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...
(midges) to be found there in the summer.
The name Mývatn is sometimes used not only for the lake but the whole surrounding inhabited area. The River Laxá, Lake Mývatn and the surrounding wetlands are protected as a nature reserve (The Mývatn-Laxá Nature Conservation Area).
Since the year 2000, a marathon around the lake takes place in summer.
Waterbirds
The lake is fed by nutrientNutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...
-rich springwater and has a high abundance of aquatic insects (Chironomidae
Chironomidae
Chironomidae are a family of nematoceran flies with a global distribution. They are closely related to the Ceratopogonidae, Simuliidae, and Thaumaleidae...
) and Cladocera
Cladocera
Cladocera is an order of small crustaceans commonly called water fleas. Around 620 species have been recognised so far, with many more undescribed. They are ubiquitous in inland aquatic habitats, but rare in the oceans. Most are long, with a down-turned head, and a carapace covering the apparently...
that form an attractive food supply for ducks. Thirteen species of ducks nest here. The duck species composition is unique in the mixture of Eurasian and North American elements and of boreal
Boreal ecosystem
The term boreal is usually applied to ecosystems localized in subarctic and subantarctic zones, although Austral is also used for the latter....
and arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...
species. Most of the ducks are migratory, arriving in late April - early May from north-western Europe. The most abundant is the Tufted Duck
Tufted Duck
The Tufted Duck, Aythya fuligula, is a medium-sized diving duck with a population of close to one million birds.- Description :The adult male is all black except for white flanks and a blue-grey bill. It has an obvious head tuft that gives the species its name.The adult female is brown with paler...
, which immigrated to Iceland at the end of the 19th century. The Greater Scaup
Greater Scaup
The Greater Scaup , just Scaup in Europe, or colloquially known as "Bluebill", for its bright blue bill, is small compared to other diving ducks, however it is larger than the closely related Lesser Scaup...
is the second most common duck species.
Other common species include the Barrow's Goldeneye
Barrow's Goldeneye
Barrow's Goldeneye is a medium-sized sea duck of the genus Bucephala, the goldeneyes. This bird was named after Sir John Barrow....
, Red-breasted Merganser
Red-breasted Merganser
The Red-breasted Merganser is a diving duck.-Taxonomy:The Red-breasted Merganser was one of the many species originally described by Linnaeus in his 18th-century work, Systema Naturae.-Description:...
, Wigeon
Wigeon
The Eurasian Wigeon, also known as Widgeon or Eurasian Widgeon is one of three species of wigeon in the dabbling duck genus Anas. It is common and widespread within its range...
, Gadwall
Gadwall
The Gadwall is a common and widespread duck of the family Anatidae.- Description :The Gadwall is 46–56 cm long with a 78–90 cm wingspan. The male is slightly larger than the female, weighing on average 990 g against her 850 g...
, Mallard
Mallard
The Mallard , or Wild Duck , is a dabbling duck which breeds throughout the temperate and subtropical Americas, Europe, Asia, and North Africa, and has been introduced to New Zealand and Australia....
, Common Scoter
Common Scoter
The Common Scoter is a large sea duck, 43-54 cm in length, which breeds over the far north of Europe and Asia east to the Olenyok River. The American/E Siberian M. americana is sometimes considered a subspecies of M. nigra.It winters further south in temperate zones, on the coasts of Europe as...
, Long-tailed duck
Long-tailed Duck
The Long-tailed Duck or Oldsquaw is a medium-sized sea duck. It is the only living member of its genus, Clangula; this was formerly used for the goldeneyes, with the Long-tailed Duck being placed in Harelda...
and Teal
Teal
Teal may mean:* Teal , a medium greenish-blue color* Various ducks:** Baikal Teal, Anas formosa** Black Teal, Aythya novaeseelandiae** Blue-winged Teal, Anas discors** Brown Teal, Anas aucklandica** Campbell Teal Anas nesiotis...
. The outflowing Laxá river has a dense colony of Harlequin Duck
Harlequin Duck
The Harlequin Duck is a small sea duck. It takes its name from Arlecchino, Harlequin in French, a colourfully dressed character in Commedia dell'arte. The species name comes from the Latin word "histrio", "actor". In North America it is also known as Lords and ladies...
s and there is a large colony of Eider
Eider
Eiders are large seaducks in the genus Somateria. Steller's Eider, despite its name, is in a different genus.The three extant species all breed in the cooler latitudes of the Northern hemisphere....
s at the river mouth some 50 km away from Lake Mývatn. The Barrow's Goldeneye is special in being the only nearctic
Nearctic
The Nearctic is one of the eight terrestrial ecozones dividing the Earth's land surface.The Nearctic ecozone covers most of North America, including Greenland and the highlands of Mexico...
duck in the area (and Iceland as a whole). Its population of about 2000 birds relies entirely on the habitat provided by the Mývatn-Laxá water system and its surrounding lava fields. Most of the Barrow's Goldeneyes overwinter there, using ice-free areas kept open by emerging spring water (both warm and cold) and in the strong river current. This species is a hole-nester, in North America using tree-holes, but at Mývatn the birds use cavities in the lava for nesting. The other duck species nest abundantly in the numerous islands of the lake and the surrounding marshlands. There is a long tradition of harvesting duck eggs for home use on the local farms. To ensure sustainability, the harvesting follows strict age-old rules of leaving at least four eggs in a nest for the duck to incubate.
Other common waterbirds include the Slavonian Grebe
Slavonian Grebe
The Horned Grebe or Slavonian Grebe, Podiceps auritus, is a member of the grebe family of water birds. The Slavonian Grebe is an excellent swimmer and diver, and pursues its fish prey underwater...
, Red-necked Phalarope
Red-necked Phalarope
The Red-necked Phalarope, Phalaropus lobatus, is a small wader. This phalarope breeds in the Arctic regions of North America and Eurasia. It is migratory, and, unusually for a wader, winters at sea on tropical oceans....
, Great Northern Diver
Great Northern Diver
The Great Northern Loon, Great Northern Diver, or Common Loon , is a large member of the loon, or diver, family of birds...
, Red-throated Diver
Red-throated Diver
The Red-throated Loon or Red-throated Diver is a migratory aquatic bird found in the northern hemisphere. It breeds primarily in Arctic regions, and winters in northern coastal waters. It is the most widely distributed member of the loon or diver family. Ranging from in length, the Red-throated...
and Whooper Swan
Whooper Swan
The Whooper Swan , Cygnus cygnus, is a large Northern Hemisphere swan. It is the Eurasian counterpart of the North American Trumpeter Swan. An old name for the Whooper Swan is Elk; it is so called in Francis Willughby and John Ray's Ornithology of 1676.-Description:The Whooper Swan is similar in...
.
The waterbird situation has been monitored annually since 1975 by the Mývatn Research Station.
Volcanism
Arctic Ocean
The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions...
about 50 km away from Mývatn. The Crater Row that was formed on top of the eruptive fissure is called Þrengslaborgir (or Lúdentarborgir) and has often been used as a textbook example of this type of volcanic activity. There was a large lake in the area at the time, a precursor of the present-day Mývatn. When the glowing lava encountered the lake some of the water-logged lake sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
was trapped underneath it. The ensuing steam explosions tore the lava into small pieces which were thrown up into the air, together with some of the lake.
By repeated explosions in a number of locations, groups of craters built up and now dominate the landscape on the shore of Lake Mývatn and also form some of the islands in the lake. This type of lava formation is known as pseudocrater
Pseudocrater
A pseudocrater is a volcanic landform which resembles a true volcanic crater, but differs in that it is not an actual vent from which lava has erupted...
s or rootless vents. A group of such craters at Skútustaðir on the south shore of the lake is protected as a natural monument and is frequented by tourists. Other pseudocrater groups in this lava field are in the Laxárdalur Valley and Aðaldalur. The formation of pseudocraters halted the advance of the lava in some places creating temporal lava lakes. The lava eventually drained from the lakes, leaving behind a forest of rock pillars. The biggest of these formations is named Dimmuborgir
Dimmuborgir
Dimmuborgir is a large area of unusually shaped lava fields east of Mývatn in Iceland. The Dimmuborgir area is composed of various volcanic caves and rock formations, reminiscent of an ancient collapsed citadel...
. At another place, Höfði, the pillars stand in the lake water. The lava created by the Þrengslaborgir eruption is known as the Younger Laxá Lava.
The Mývatn district lies on the western border of the volcanic zone which cuts across north-eastern Iceland from north to south and is an extension of the Mid-Atlantic Ridge
Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. It separates the Eurasian Plate and North American Plate in the North Atlantic, and the African Plate from the South...
. All geological formations are quite recent, dating from the Ice Age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
and postglacial times.
The bedrock
Bedrock
In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil...
of the moors west of Lake Mývatn is made up of interglacial
Interglacial
An Interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age...
lava flows. Most of the mountains in the vicinity of the lake were formed by eruptions under the ice sheet in the glacial periods of the Ice Age. Eruptions that melted their way up through the ice formed table mountain
Table (landform)
A table, when used in reference to landforms, is a hill, flank of a mountain, or mountain, that has a flat top.This landform has numerous names in addition to "table", including:*Tuya*Tepui*Mesa*Potrero*Butte*Plateau*Terrace-Description:...
s (Mounts Bláfjall, Sellandafjall, Búrfell, Gæsafjöll), those which didn't formed hyaloclastite
Hyaloclastite
Hyaloclastite is a hydrated tuff-like breccia rich in black volcanic glass, formed during volcanic eruptions under water, under ice or where subaerial flows reach the sea or other bodies of water. It has the appearance of angular flat fragments sized between a millimeter to few centimeters...
ridges (Mounts Vindbelgjarfjall, Námafjall, Dalfjall, Hvannfell).
At the close of the Ice Age, about 10,000 years ago, the Mývatn basin was covered by a glacier which pushed up huge end moraines which can still be seen at the north end of the lake. After the glacier started melting, a glacial lake
Glacial lake
A glacial lake is a lake with origins in a melted glacier. Near the end of the last glacial period, roughly 10,000 years ago, glaciers began to retreat. A retreating glacier often left behind large deposits of ice in hollows between drumlins or hills. As the ice age ended, these melted to create...
was dammed up in the Mývatn depression until the glacier retreated from the present course of Laxá river.
Postglacial volcanism in the Mývatn district may be divided into three cycles. The Lúdent cycle commenced shortly after the close of the Ice Age. The explosion crater (tephra
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....
ring) Lúdent dates from this cycle. Its eruption was followed by a number of small fissure eruptions. About 3800 years ago the shield volcano
Shield volcano
A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes...
Ketildyngja was formed about 25 km south-east of Mývatn, and from it a huge lava flow, the Older Laxá-lava, spread over the southern part of the district, plunged down the Laxárdalur valley and flowed almost to the sea. This lava dammed up the first Mývatn, which was about as large as the present lake.
The second volcanic cycle, the Hverfjall cycle, began 2500 years ago with a gigantic but brief eruption, which formed the explosion crater (tephra ring ) Hverfjall
Hverfjall
Hverfjall is a tephra cone or tuff ring volcano in northern Iceland, to the east of Mývatn.It erupted in 2500 BP in the southern part of the Krafla fissure swarm. The crater is approximately 1 km in diameter....
(also named Hverfell). An eruption in Jardbadshólar followed, producing the lavafield between Reykjahlíð and Vogar. Approximately 200 years later a vast lava flow, the Younger Laxá-lava, was erupted (see above). The lava dammed up the present Lake Mývatn and also the lakes Sandvatn, Grænavatn and Arnarvatn.
The third volcanic cycle began with the Mývatnseldar eruptions in 1724-1729 which commenced with an explosion that formed the crater lake
Crater lake
A crater lake is a lake that forms in a volcanic crater or caldera, such as a maar; less commonly and with lower association to the term a lake may form in an impact crater caused by a meteorite. Sometimes lakes which form inside calderas are called caldera lakes, but often this distinction is not...
Víti. Later lava flowed from Leirhnjúkur down to the north end of Lake Mývatn, destroying two farms. The Mývatnseldar eruptions are quite similar in character to the recent volcanic activity near Krafla in 1975-1984. The source of both is a central volcano lying between Krafla and Gæsafjöll. Inside the volcano resides a magma chamber
Magma chamber
A magma chamber is a large underground pool of molten rock found beneath the surface of the Earth. The molten rock in such a chamber is under great pressure, and given enough time, that pressure can gradually fracture the rock around it creating outlets for the magma...
from which molten magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
periodically bursts into a swarm of fissures that cut through the volcano from north to south.
The recent activity was characterized by periods of slow land rise, interspersed by shorter periods of rapid subsidence, underground magma bursts, rifting, earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
s and eruptions (nine in all). This is an excellent example of the process of continental drift
Continental drift
Continental drift is the movement of the Earth's continents relative to each other. The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912...
in Iceland. A central volcano and its associated fissure swarm is called a volcanic system. The Krafla volcanic system is one of several such systems which together form the volcanic zone of Iceland.
A few rhyolite
Rhyolite
This page is about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade.Rhyolite is an igneous, volcanic rock, of felsic composition . It may have any texture from glassy to aphanitic to porphyritic...
mountains border the Krafla central volcano (Mounts Hlíðarfjall, Jörundur, Hrafntinnuhryggur).
Because of the volcanic origin, there are silica quarries in the lake.
Plants
Lake Mývatn is one of the few places in the world that grows MarimoMarimo
, also known as Cladophora ball, Lake ball, or Moss Balls in English, is a species of filamentous green algae found in a number of lakes in the northern hemisphere. A marimo is a rare growth form of the species where the algae grow into large green balls with a velvety appearance...
, also known as Cladophora ball, Lake ball, or Moss Balls in English, a species of filamentous green algae (Chlorophyta).
See also
- Lakes of Iceland
- Volcanism in Iceland
- Geography of IcelandGeography of IcelandIceland is a medium-sized island in the North Atlantic ocean. The island is located east of Greenland and immediately south of the Arctic Circle, atop the divergent boundary of the Mid-Atlantic Ridge in the North Atlantic Ocean. It lies about from New York City and from Scotland...
- CladophoraCladophoraCladophora is a genus of reticulated filamentous Ulvophyceae . The genus Cladophora contains many species that are very hard to tell apart and classify, mainly because of the great variation in their appearances, which is affected by habitat, age and environmental conditions...
External links
- Geological maphttp://www.hi.is/HI/Stofn/Myvatn/geomap.htm
- A complete bibliography on the natural history of Mývatnhttp://www.hi.is/HI/Stofn/Myvatn/myreflst.htm
- Current seismic activity at Mývatnhttp://hraun.vedur.is/ja/englishweb/myvatn.html
- Lake Myvatn images
- Facts and photos
- Photoshttp://www.eas.ualberta.ca/elj/icepics/pseudo.htmhttp://www.bildungsservice.at/faecher/geo/Staaten%20und%20Landschaften/Island/Island%202/Island%201996-0040%20-%20Myvatn%20-%20Pseudokrater.JPG
- Seacology Lake Myvatn Project SeacologySeacologySeacology is a nonprofit 501 charitable organization headquartered in Berkeley, California that focuses on preserving island ecosystems and cultures around the globe. Founded in 1991, it began with the work of ethnobotanist Paul Alan Cox, who researched tropical plants and their medicinal value in...
- Mývatn panoramic virtual tour
