 | This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Maar" – news ·newspapers ·books ·scholar ·JSTOR(May 2024) (Learn how and when to remove this message) |
Amaar is a broad, low-reliefvolcanic crater caused by aphreatomagmatic eruption (an explosion which occurs whengroundwater comes into contact with hotlava ormagma). A maar characteristically fills with water to form a relatively shallowcrater lake, which may also be called a maar.[1]
Maars range in size from 20 to 3,000 m (66 to 9,800 ft) across and from 5 to 200 m (20 to 700 ft) deep.[2][3] Most maars fill with water to form natural lakes. Most maars have low rims composed of a mixture of loose fragments ofvolcanic rocks and rocks torn from the walls of thediatreme.[3]
The namemaar comes from aMoselle Franconian dialect word used for the circular lakes of theDaun area of Germany. The word evolved from its first use in German in the modern geological sense in 1819 and is now used in English and in the geological sciences as the term for the explosion crater, even if water from rainfall might always have drained from the crater after the formation event. This extension in meaning was due to recognising that the lake may no longer exist. Since maar lakes are formed after initially ground or subsurface water interacts with amagma intrusion to create an explosion crater, the name came to be used for the crater type as well.[Note 1] The present definition of the term[1] relates to both its common and scientific discourse use in language over two centuries. Depending upon context there may be other descriptors available to use in the geological sciences such as the term tuff ring ormaar-diatreme volcanoes.[4] These last are volcanoes produced by explosive eruptions that cut deeply into the country rock with the maar being "the crater cut into the ground and surrounded by an ejecta ring".[4] A 2011 geological clarification of a maar is "Maar volcanoes are distinguished from other small volcanoes in having craters with their floor lying below the pre-eruptive surface".[4]
Maar lakes, also referred to simply asmaars, occur whengroundwater orprecipitation fills the funnel-shaped and usually round hollow of the maar depression formed by volcanic explosions. Examples of these types of maar are the three maars at Daun in theEifel mountains ofGermany.
Adry maar results when a maar lake dries out, becomesaggraded orsilted up. An example of the latter is theEckfelder Maar. NearSteffeln is theEichholzmaar (also called theGussweiher) which has dried out during the last century and is being renaturalised into a maar. In some cases the underlying rock is so porous that maar lakes are unable to form. After winters of heavy snow and rainfall many dry maars fill partially and temporarily with water; others contain smallbogs or often artificial ponds that, however, only occupy part of the hollow.[citation needed]
The largest known maars are found atEspenberg on theSeward Peninsula in northwest Alaska. These maars range in size from 4 to 8 km (2.5 to 5.0 mi) in diameter and a depth up to 300 m (980 ft). These eruptions occurred in a period of about 100,000 years, with the youngest (the Devil Mountain Maar) occurring about 17,500 years ago. Their large size is due to the explosive reaction that occurs whenmagma comes into contact withpermafrost. Hydromagmatic eruptions are increasingly explosive when the ratio of water to magma is low. Since permafrost melts slowly, it provides a steady source of water to the eruption while keeping the water to magma ratio low. This produces the prolonged, explosive eruptions that created these large maars. Examples of the Seward Peninsula maars include North Killeak Maar, South Killeak Maar, Devil Mountain Maar and Whitefish Maar.[5]
Maars occur in western North America,Patagonia in South America, theEifel region ofGermany (where they were originally described), and in other geologically young volcanic regions of Earth. Elsewhere in Europe, La Vestide du Pal, a maar in theArdèche department of France, is easily visible from the ground or air.Kilbourne Hole and Hunt's Hole, in southernNew Mexico nearEl Paso, Texas, are maars. The Crocodile Lake inLos Baños in the Philippines, though originally thought to be a volcanic crater, is a maar. Thecarbon dioxide-saturatedLake Nyos in northwesternCameroon is another example, as isZuñi Salt Lake inNew Mexico, a shallowsaline lake that occupies a flat-floored crater about 6,500 ft (2,000 m) across and 400 ft (120 m) deep. Its low rim is composed of loose pieces ofbasaltic lava andwall rocks (sandstone,shale,limestone) of the underlyingdiatreme, as well as chunks of ancientcrystalline rocks blasted upward from great depths. Maars inCanada are found in theWells Gray-Clearwater volcanic field of east-centralBritish Columbia and inkimberlite fields throughout Canada. Another field of maars is found in thePali-Aike Volcanic Field inPatagonia, South America.[6] and in the SudaneseBayuda Volcanic Field. TheAuckland volcanic field in the urban area ofAuckland, New Zealand, has several maars, including the readily accessibleLake Pupuke in the North Shore suburb ofTakapuna.
Arizona'sMeteor Crater was for many years thought to be a maar of volcanic origin but it is now known to be animpact crater.[7]
In theVolcanic Eifel there are about 75 maars. Both lake-filled and dry maars are typical, though the latter are more common. The last eruptions took place at least 11,000 years ago, and many maars are older, as evidenced by their heavyerosion and less obvious shapes and volcanic features.[8]
In the Eifel and Volcanic Eifel there are numerous dry maars:
The following volcanic features are often colloquially referred to as a "maar" or "maar lake", although they are not, strictly speaking, maars:
In Germany there are also several maars outside of the Eifel. A well-known example is theMessel pit, a former maar lake nearMessel in the county ofDarmstadt-Dieburg and which is known for its well preservedfossils. In addition in theSwabian Jura and theAlbvorland (the Swabian Volcano) there are maar-forming volcanoes. Because the over 350 eruption points were only active in the UpperMiocene 17 to 11 million years ago, all the maars, apart from the dry maar,Randecker Maar and the Molach, are only detectable geologically. In theOre Mountains nearHammerunterwiesenthal, the Hammerunterwiesenthal Maar formed about 30 million years ago during the Oligocene; the maar measures 2 kilometres from east to west and 1.4 kilometres from north to south.
TheChaîne des Puys in France contains numerous maars;Lake Albano in theAlban Mountains is a complex maar, and there is also a submarine maar (Kolumbo) nearSantorini in Greece. TheCampo de Calatrava Volcanic Field in Spain contains numerous maars; a typical example being the maar of Hoya del Mortero at Poblete in theProvince of Ciudad Real.
Active maars were commonplace inFife andLothian, Scotland during theCarboniferous period.[11] The location of one such maar was Elie Ness.[12]
Active maar volcanoes are mainly known outside Europe.
In the US there are numerous maar areas, such as in Alaska (Ukinrek maars,Nunivak in theBering Sea); inWashington (Battle Ground Lake); inOregon (Fort Rock basin with the maars ofBig Hole,Hole-in-the-Ground,Table Rock); inDeath Valley National Park,California (Ubehebe Crater); inNevada (Soda Lakes); as well as the maars of theWhite Rock Canyon,Mount Taylor, thePotrillo volcanic fields (Kilbourne Hole andHunt's Hole), andZuñi Salt Lake in New Mexico.
In Central Mexico, the Tarascan volcanic field contains several maars in the states ofMichoacán andGuanajuato. TheRío Cuarto andHule maars are in Costa Rica. In Nicaragua is the maar of Laguna de Xiloa, part of theApoyeque volcano. From South America, there are known maars inChile (e.g.Cerro Overo andCerro Tujle in northern Chile).Jayu Khota is a maar inBolivia.
The maar ofLake Ram[13] lies on theGolan Heights; further south maars occur in Africa (Bilate Volcanic Field andHaro Maja in theButajiri-Silti-Volcanic Field, Ethiopia, theBayuda Volcanic Field in the Sudan andLake Nyos in theOku Volcanic Field in Cameroon). InSaudi Arabia theAl Wahbah crater formed as a result of a maar eruption.[14]
In Japan there are maars in theKirishima-Yaku volcanic field in theKirishima-Yaku National Park onKyushu. These include the several maars of theIbusuki volcanic field such asLake Unagi.[15] OnHonshu inMyōkō-Togakushi Renzan National Park there is Kagamiike Pond as well as many on the volcanic island ofMiyake-jima,Izu Islands (Furumio, Mi'ike, Mizutamari, Shinmio).[citation needed]
Koranga Maar and Numundo Maar are inPapua New Guinea.[citation needed] Kawah Masemo maar is onMount Sempu volcano in Indonesia.[citation needed] The San Pablo Volcanic Field in theProvince of Laguna on the island ofLuzon in the Philippines contains maars.[citation needed]
TheNewer Volcanics Province in the States ofSouth Australia andVictoria, Australia, has numerous maars, such asMount Gambier,Mount Schank andTower Hill, whose complex system of nested maars is enclosed by one of the largest maars in the world.[16][17]
Foulden Maar inOtago,New Zealand, is an important fossil site,[18] but there are many more maars in New Zealand. As already mentioned these includeLake Pupuke, but theAuckland volcanic field has other easily accessible maars such as theMangere Lagoon,Orakei Basin,Panmure Basin, andPukaki Lagoon. Elsewhere a recent example, only 4000 years old, isLake Rotokawau in theBay of Plenty Region.[19][better source needed]
![El Muweilih Crater, a maar in Bayuda volcanic field, Sudan:[20] Natron-rich clay on the crater floor](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aBVFMuweilihCrater.jpg)
| Types |  | |
|---|---|---|
| Volcanic rocks | ||
| Lists and groups | ||
