Maar
A maar ( Latin mare , sea ) is a bowl-shaped or funnel-shaped hollow of volcanic origin that is sunk into a pre-volcanic land area. It was formed by water vapor explosions when groundwater and hot magma met , in most cases in a single explosion period. Maars are predominantly circular or oval, the hollow can be flat or funnel-shaped like a crater. As a rule, the maar is surrounded by a ring wall made of ejecta. One distinguishes the maar lake from the dry maar .
The sediments found in maars give researchers insights into the earth's climatic past by means of sedimentological studies .
Origin of name
The name Maar is most likely derived from the Eifel dialect of the same name from the Daun area. One of the first written mentions is the application of the word Marh to the Ulmener Maar and (incorrectly in today's sense of the word, because it is a caldera ) the Laacher See by Sebastian Münster in his book Cosmographia . The Trier geologist and high school teacher Johannes Steininger (1794–1874) picked up this dialect name and was the first to use it accordingly in geological literature (a volcanic funnel usually filled with water ). This term later entered international terminology. The derivation of the Latin mare "sea", late Latin mara "lake" is obvious.
Structure and creation
The formation of maars has long been controversial, but has been clarified on the basis of observations on active maar volcanoes around the Pacific.
Maars are formed in a phreatomagmatic explosion when water ( ground or surface water ) meets hot molten rock (magma). The resulting explosion leads to the rapid ejection of tuff material , which in some cases consists almost entirely of shattered non-volcanic secondary rock; in any case, a proportion of secondary rock can be found in the ejected tuffs. The tuffs can form a wall around the edge of the maar, extend from the maar in irregularly distributed tuff fans or cover the area around the maar as a tuff cover. Typical maars are between 50 and 2000 m in diameter, even larger maars are known.
The size of the maar essentially depends on the amount of water supplied. If there is little water, the center of the explosion is close to the earth's surface at a depth of about 30 to 100 m. The blasted out funnel of the explosion crater is several hundred meters tall, its volume corresponds to that of the ejected material. If the amount of water is large, because a water-rich stream or lake runs into the volcanic vent, the water can reach greater depths and the explosion takes place at a depth of up to 500 m. It cannot completely clear the rock above it, so that the rock shattered in the explosion breaks upwards in narrow explosion channels and crevices and is ejected there as a tuff jet or fan, while the emptied cavity finally collapses. Explosions of this type create maars more than 1000 m in diameter.
Maar lakes and dry maars
In the maar lake , the groundwater or rainwater fills the funnel-shaped and mostly round hollow shape of the maar basin, which was created by the volcanic explosions. Examples of this type of maar are the three Dauner Maars in the Eifel. A dry maar is a ( silted up ), landed or drained maar lake filled with sediment . A silted up maar lake is, for example, the Eckfelder Maar . At Steffeln , the Eichholzmaar (also called "Gussweiher"), which was drained in the last century, has been renatured to a maar again. In some cases the subsoil is so permeable that no maar lake can form. After snowy winters and heavy rainfall, some dry maars partially and temporarily fill with water, others contain small moors or often artificially created ponds, which, however, only take up parts of the hollow form.
Differentiation from other volcanic forms
The volcanic type of the maar can be distinguished from similar volcanic forms as follows:
- In contrast to crater lakes , maars are sunk into a non-volcanic surface. No or seldom lava flows emanate from it.
- Unlike calderas , maars are not created by the collapse of a magma chamber . The ejection of rock material from deeper regions during a maar eruption can cause the surface to collapse, but the remains of a volcanic cone or other volcanic buildings are missing, as are indications of a longer period of origin.
- In contrast to the diatreme , a maar has a funnel or crater sunk into the surface of the earth.
- the ejected pyroclastic rocks or the tephra are comparatively rich in adjacent rocks or poor in lava fragments and bombs.
Occurrence
In Germany
Eifelmaare
In the Vulkaneifel there are around 75 maars, both as water-filled maar lakes, but in the vast majority of cases as dry maars. Both maar forms are typical for the Vulkaneifel . The last eruptions were at least 11,000 years ago and many maars in the Eifel are significantly older. For this reason, many are already severely eroded and their shapes and volcanic features are not as clear as is the case with younger or even active maars elsewhere on earth. Nevertheless, the maars of the Eifel are well preserved. The water-filled maars are also known as the (blue) eyes of the Eifel .
Water-filled maars of the Eifel
| Name geo-coordinates |
Location at / between |
Area in ha |
Depth in m |
annotation |
|---|---|---|---|---|
| Eichholzmaar ( ⊙ ) | Duppach , Steffeln | 1.1 | 3.2 | Smallest, permanent Eifelmaarsee |
| Gemündener Maar ( ⊙ ) | Gemünden | 7th.2 | 39.0 | |
| Holzmaar ( ⊙ ) | Eckfeld , Gillenfeld | 6th.8th | 21st.0 | A stream flows through it |
| Immerather Maar ( ⊙ ) | Immerath , Strotzbüsch | 6th.0 | 2.9 | Shallowest depth of all Eifelmaar lakes |
| Meerfelder Maar ( ⊙ ) | Deudesfeld , Meerfeld | 24.0 | 17th.0 | |
| Pulvermaar ( ⊙ ) | Gillenfeld , Immerath | 38.48 | 72.0 | Deepest and largest maar lake in Germany |
| Schalkenmehrener Maar ( ⊙ ) | Gemünden , Schalkenmehren | 21st.6th | 21st.0 | |
| Ulmener Maar ( ⊙ ) | Elms | 6th.0 | 37.0 | The youngest maar in the Eifel |
| Weinfelder Maar ( ⊙ ) | Gemünden , Schalkenmehren | 16.8th | 51.0 | Also called Totenmaar |
Map with all coordinates: Dry maars of the Eifel
There are also numerous dry maars in the Eifel and Vulkaneifel:
- Mosbrucher Weiher (4 km southeast of Kelberg )
- Booser Doppelmaar (west of Boos ; near Kelberg)
- Dreiser Weiher (west of Dreis-Brück , north of Daun )
- Dürres Maar (southwest of Gillenfeld )
- Duppacher Weiher (near Duppach , northwest of Gerolstein )
- Geeser Maar (east of Gerolstein , north of the Gees district)
- Eckfelder Maar (near Eckfeld )
- Eigelbacher Maar (near Kopp , Daun district ; Maarkessel: approx. 1200 m × 1200 m)
- Hitsche Maar (northwest of Dürren Maar, smallest Eifelmaar; Ø = 60 m)
- Immerather Risch (das; mnd. "Risch" = reed bed; north of the Immerather Maar)
- Gerolsteiner Maar (northeast of Gerolstein )
- Schönfelder Maar (southwest of Stadtkyll -Schönfeld)
- Steffelner Laach or "Laach Maar" (near Steffeln )
- Dehner Maar (near Reuth )
- Walsdorfer Maar ("Schilierwiese"; south of Walsdorf ; Maarkessel: approx. 1150 m × 1000 m)
- Wollmerather Maar (near Wollmerath )
Different use of the term maar
The volcanic forms mentioned below are often commonly referred to as “maar” or “maar lake”, although they are not actually maars:
- Windsborn crater lake and Hinkelsmaar in the Manderscheider volcanic group near Bettenfeld , crater lakes of the Mosenberg
- Laacher See near Maria Laach , lake in the collapse crater (caldera) of the Laacher See volcano
- Strohner Maarchen (south of the powder maar ), slag chimney converted into maar
- Papenkaule , a volcanic crater , and the associated eruption site of the Hagelskaule
- Elfenmaar in Bad Bertrich , an almost completely worn Stratovolcano
- Rodder Maar near Niederdürenbach , origin unclear.
Maars outside the Eifel
In Germany there are also some maars outside of the Eifel. A famous example of this is at Messel in Darmstadt-Dieburg Located Messel Pit , a former crater lake, which by its well-preserved fossils is known. There were also maar-forming volcanoes on the Swabian Alb and in the foothills of the Alb ( Swabian volcano ); Since the more than 350 eruption points were only active in the Upper Miocene 17 to 11 million years ago, all maars except for the dry maar Randecker Maar and the Molach can only be found geologically. In the Ore Mountains near Hammerunterwiesenthal , the Maar of Hammerunterwiesenthal was formed around 30 million years ago during the Oligocene , which is 2 km long in east-west direction and 1.4 km wide in north-south direction.
Outside of Germany
Maars can also be found elsewhere in Europe. The Chaîne des Puys in France , for example, contains numerous maars, Lake Alban in the Alban Hills is a complex maar, and a maar is also known from Santorini in Greece (Colombo). The volcanic area of Campo de Calatrava in Spain contains numerous maars, a typical example is the maar of Hoya del Mortero near Poblete in the province of Ciudad Real .
Active maar volcanoes are mainly known outside of Europe. There are numerous maar areas in the USA, for example in Alaska ( Ukinrek Maare , Nunivak in the Bering Sea ), in Washington ( Battle Ground Lake ), in Oregon ( Fort Rock Basin with the maars Big Hole , Hole-in-the-Ground , Table Rock , Seven-Mile Ridge ), in Death Valley National Park ( Ubehebe Crater ) and the maars of White Rock Canyon , Mount Taylor and Potrillo Volcanic fields, Zuni Salt Lake Crater and Kilbourne Hole Crater in New Mexico.
In central Mexico, the Tarascan volcanic field in the states of Michoacán and Guanajuato contains several maars. The maar of Laguna Aramuaca can be found in El Salvador . Maars are known from South America in Chile , for example ( Carrán - Los Venados in Central Chile, Cerro Overo and Cerro Tujle in Northern Chile). The Laguna Jayu Khota is a maar in Bolivia .
The maar of Birket Ram is located on the Golan Heights , further south there are maars in Africa ( Bilate volcanic field and Haro Maja in the Butajiri - Silti volcanic field, Ethiopia, the Bayuda volcanic field in Sudan and Lake Nyos in the Oku volcanic field in Cameroon).
In Siberia, the Kinenin Maar and the Maar of Lake Dal'ny are among the volcanoes on the Kamchatka Peninsula. In Japan there are maars in the Kirishima - Yaku volcanic field in the Kirishima-Yaku National Park on Kyushu (Kagamiike Pond) and numerous on the volcanic island of Miyake-jima , Izu Islands (Furumio, Mi'ike, Mizutamari, Shinmio).
The Newer Volcanics Province in Victoria Province , Australia contains numerous maars, such as Mount Gambier and Mount Schank . The Koranga is known in Papua New Guinea , and the Numundo Maar is in the Krummel-Garbuna-Welcker volcanic field in New Britain . The Kawah Masem on Sempu in Indonesia is also a maar, and the San Pablo Volcanic Field in Laguna Province on Luzon Island in the Philippines contains maars.
See also
literature
- Werner D'hein: Nature and culture guide Vulkanland Eifel. With 26 stations on the "German Volcano Road". Gaasterland-Verlag, Düsseldorf 2006, ISBN 3-935873-15-8 .
- Hans-Ulrich Schmincke: Vulcanism . Primus-Verlag, Darmstadt 2010, ISBN 978-3-89678-690-6 , p. 184.
- Wilhelm Meyer: Geology of the Eifel . 1st edition. Schweizerbart'sche Verlagbuchhandlung, Stuttgart 1986, ISBN 3-510-65127-8 .
Web links
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- Maarmuseum Manderscheid
- The treasure in the crater lake , article on the Baruther Maar in Saxony, in the geosciences portal, on planeterde.de
- Volker Lorenz: Maar-Diatreme Volcanoes, their Formation, and their Setting ... (PDF; 2.15 MB; English)
- Jack Share: Anatomy of a Cinder Cone Roadcut in the Land of Cochise and Its Tale of Farallon Plate Geo-Gymnastics - Part I , in the blog Written in Stone… seen through my lens - u. a. Description of maars with schematic representation, on blogspot.de (English)
References and comments
- ↑ a b c Wilhelm Meyer: Geology of the Eifel . 1st edition. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart 1986, ISBN 3-510-65127-8 , pp. 311, 311 f .
- ↑ Ute Kehse: From sandstorms to the ice age. In: Image of Science. August 12, 2005, accessed on September 8, 2019 (maars in the Eifel recorded climate change before the last cold spell).
- ^ Franz Ossing: Climate research in dead volcanoes. GeoForschungsZentrum Potsdam, May 13, 1996, accessed on October 6, 2017 .
- ^ H. Wolfgang Wagner et al .: Trier and surroundings (= collection of geological guides . Volume 60 ). 3rd, completely revised edition. Borntraeger, Stuttgart 2012, ISBN 978-3-443-15094-5 (geology of the south and west Eifel, south-west Hunsrück, the lower Saar as well as maar volcanism and recent environmental and climate history).
- ↑ ksta.de
- ↑ The depth of the maars at medium water levels
- ^ Wilhelm Meyer: The geology. (No longer available online.) In: Heimatjahrbuch 2006. Ahrweiler district, archived from the original on May 25, 2016 ; Retrieved on January 21, 2016 (on unclear origin of the Rodder Maar ).
- ^ Neumann et al .: Holocene vegetation and climate history of the northern Golan heights (Near East) . In: Vegetation History and Archaeobotany . tape May 16 , 2007, pp. 329–346 , doi : 10.1007 / s00334-006-0046-x (English).