The Meerfelder Maar is a

maar A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow ...

by the village of Meerfeld not far from the town of Manderscheid in the

Eifel The Eifel (; , ) is a low mountain range in western Germany, eastern Belgium and northern Luxembourg. It occupies parts of southwestern North Rhine-Westphalia, northwestern Rhineland-Palatinate and the southern area of the German-speaking Com ...

in the German state of

Rhineland-Palatinate Rhineland-Palatinate ( , ; ; ; ) is a western state of Germany. It covers and has about 4.05 million residents. It is the ninth largest and sixth most populous of the sixteen states. Mainz is the capital and largest city. Other cities are ...

Formation

The maar is at least 30,000 years old and, according to the more recent information, is probably even 40,000 years old. In 1978 the lake deposits were investigated in order to determine its exact age. Numerous borings have been carried out in the Meerfelder Maar right up to the present day. It was formed by a huge underground phreatomagmatic explosion that happened when hot

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

rose and struck a water-laden layer of rock. The explosive evaporation of the water crushed the surrounding rock and threw some of it upwards. The resulting hollow filled up again with rock and a funnel-shaped sink-hole formed at the surface. The

magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it u ...

, from which the magma rose, lies about 2,000 to 6,000 metres below the Meerfelder Maar.

Structure

The whole crater has a diameter of 1,400 metres from east to west and 1,200 metres from north to south, and is about 125

hectare The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm2), that is, square metres (), and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. ...

s in area. It is thus one of the larger maars in the Eifel. The highest part of the crater rim lies at a height of , where there is an

observation tower An observation tower is a tower used to view events from a long distance and to create a full 360 degree range of vision to conduct long distance observations. Observation towers are usually at least tall and are made from stone, iron, and woo ...

, the ''Landesblick'' ("countryside view"). Half of the maar basin is filled today by the maar lake. The village of Meerfeld lies at the southern edge of the basin, still within the hollow created by the eruption.

Maar lake

Over the course of time the maar has filled with water and formed the present day maar lake which has a maximum depth of 17 metres. It is 780 metres long (west to east) and 490 metres wide (north to south). The surface of the lake is . From 1877 to 1880 the water level of the lake was artificially lowered in order to create meadows and pasture land. The cost of 12,000

gold marks The German mark ( ; sign: ℳ︁) was the currency of the German Empire, which spanned from 1871 to 1918. The mark was paired with the minor unit of the pfennig (₰); 100 pfennigs were equivalent to 1 mark. The mark was on the gold standar ...

was paid by the state and the province, which is why the municipality Meerfeld erected a commemorative monument in 1890. Since the early 20th century the maar lake has suffered from overfertilization of the area and become polytrophic. Until 1984 the water was very dark during the summer months and had a yellow and brown colouration that was due to

blue algae Blue is one of the three primary colours in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model. It lies between violet and cyan on the spectrum of visible light. The term ''blue'' generally descr ...

. In 1982 the Meerfelder Maar was therefore cleaned by deep draining (''Tiefenentwässerung''). The lake itself is increasingly

silting up Siltation is water pollution caused by particulate terrestrial clastic material, with a particle size dominated by silt or clay. It refers both to the increased concentration of suspended sediments and to the increased accumulation (temporary or ...

. This is reflected in its vegetation. In the shore regions there are large areas where water-loving plants such as bulrushes,

reeds Reed or Reeds may refer to: Science, technology, biology, and medicine * Reed bird (disambiguation) * Reed pen, writing implement in use since ancient times * Reed (plant), one of several tall, grass-like wetland plants of the order Poales * Re ...

, club rushes,

water lilies ''Water Lilies'' ( ) is a series of approximately 250 oil paintings by French Impressionist Claude Monet (1840–1926). The paintings depict his flower garden at his home in Giverny, and were the main focus of his artistic production during ...

water hemlock ''Cicuta'', commonly known as water hemlock, is a genus of four species of highly poisonous plants in the family Apiaceae. They are perennial herbaceous plants which grow up to tall, having distinctive small green or white flowers arranged in a ...

and yellow irises are growing. There are about 15 species of fish. A fishing licence may be obtained in any of the restaurants in the municipality. Since 1986 the maar and its wet-dry shoreline areas as well as the deciduous forest in the area of the maar basin have been declared a

nature reserve A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, funga, or features of geologic ...

References

Literature

* Martina Stebich: ''Palynologische Untersuchungen zur Vegetationsgeschichte des Weichsel-Spätglazial und Frühholozän an jährlich geschichteten Sedimenten des Meerfelder Maares (Eifel)''. Dissertationes Botanicae 320, Stuttgart 1999, . * Werner P. D´hein: ''Vulkanland Eifel. Natur- und Kulturführer, mit 26 Stationen der "Deutschen Vulkanstraße".'' Gaasterland-Verlag, Düsseldorf, 2006, , . * Negendank, J.F.W. et al.: ''The Meerfelder Maar Lake Deposits''. Zeitschrift für Gletscherkunde und Glazialgeologie, 21, 67-70, 1985
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External links