The deepest "Eye of the Eifel"

The vernacular expression in the Eifel for a lake of volcanic origin in the region is ‘Maar’, in English: crater. Their proximity, round forms and considerable depth made people aware early on of their special nature, even though only modern life with a view from a plane or hot-air balloon discloses the full charm and secret of their beauty: ‘Maare’ are the Eyes of the Eifel.


How old is a ‘Maar’?

The oldest volcanic action goes back some 40 to 50 million years (Eckfelder Maar). Modern landscape was formed by much more recent volcanoes which belong to the geological present. All ‘Maare‘ date back to prehistory when climate changed between warm and cold periods and when early man came to Europe. For more than 600 000 years volcanic activities existed, and the ‘Maare’ we know now belong to the most recent phase. On average they are somewhere between 10 000 and 30 000 years old, with the Neanderthal being the first to witness their formation. The most recent eruption of the Laacher volcano which led to the forming of the Laacher See (East Eifel) can be dated back to 10 960 BC. The eruption hurled masses of pumiceous lava into the Rhine valley, with water rising and ashes and dust blown as far as the Baltic states. Pumice buried a camp of red deer hunters of the final Ice age time - as disastrous for the people then as the eruption of Mt. St. Helens today.


How was a ‘Maar’ formed?

The volcanoes of the Eifel cannot be compared with Mt. Etna, for example, where one sees an open magma field boiling and lava flowing. The volcanic centre in a ‘Maar’ lies at great hidden depths. In the volcanic region of the Eifel, from Bad Bertrich to as far away as the Belgian border, we find rocks being heated by hot gases at a depth of some 400km (Eifel-Plume). When these hot vapours meet ground water or surface water caught in crevices and caves, pressure has to be released in the form of an eruption due to differences in temperature and pressure. The force behind these explosions varied as seen in the many different forms of crater funnels, some small or larger, shallow or deeper. In a deep crater, with additional cavities giving way after the explosion, we find the ideal prerequisite for a future ‘Maar’, especially when water-resisting sediments have encouraged a build-up of groundwater allowing a lake of considerable depth to form ( see drawing).

The Pulvermaar, with a depth of more than 80m in places, is the "deepest eye” and also the deepest lake north of the Alps. These 80 meters are only a fraction of the original depth of the crater which geologists estimate at 300m. The power of numerous explosions over a period of several weeks or months must have been breathtaking for the people of the Eifel, turning day into night and leaving a 100m high wall of debris, ash and stones (lapilli). Later on, more than 13 million cubic meters of water collected within the funnel. Because of its great depth, the temperature remains a constant + 4 C.


The Changes of a ‘Maar’.

The craters were at first uninhabited, containing barren water in rough volcanic cinders caught between walls of pumice and lapilli. Both ground and water were perilous: sterile and without humus the ground, cold, deep and traversed by rising gases the later. Since without tributary, life had to be brought in by air – indeed by birds. The steepness of the funnel caused a strong wash, resulting in continuously subsiding slopes, and the ’Maar’ eventually filled with soil, with more than half of the original funnel of the Pulvermaar disappearing. In several thousands of years only a flat lake will remain.
The Strohner Märchen and also the Dürremaar on the other side of Gillenfeld with their rare moor vegetation are proof of the transition from ‘Maar’ to land. The Immerather Maar dried out, becoming arable land during the 1940’s, and was used as a potato field. Later on, for touristic reason, new consideration was given to the area as an important natural land form and further farming was curtailed..
Nowadays a walk starting at the Pulvermaar, past the Römerberg, a true volcano with scoria, to the Strohner ‘dry-Maar’ and further on to the Immerather Maar or Immerather Risch shows all the changes a ‘Maar’ goes through - from being a deep lake to becoming a land-filled hollow.

The Future

What will the future bring?

Only very few indications of volcanic activities in the region are recognisable. Spectacular is the Simmering Well (Wallender Born) in Wallenborn, an active spring with periodic changes between water and vapour eruptions, and dormancy. Furthermore there are a number of places where gases of volcanic origin escape, especially the deadly CO2, in a dry state known as Mofetten, or as carbonic acid spring water (Drees). Best known are the waters of the Eifeler Sauerbrunnen which contain iron, sodium and chloride, and the thermal springs of Bad Bertrich. Even though the days of lava, fire and clouds of ashes and dust have gone – the volcanicity of the Eifel has not become extinct. The high number of volcanoes and ‘Maare’ in a small area, active over a long period of time, is evidence. There have been some six hundred events during 600 000 years – averaging one per thousand years. Activities came and went, and it is certain that we live in a phase of dormancy lasting now 10 000 years.

At some future time there might be another Ice age and some time later another volcano might explode as the gases (the Plume) deep down are still hot. At the moment science can neither explain nor predict how and when this heated matter will be raised to the surface and ejected. The proximity of vapours, superheated and under pressure, pushing their way up at different times and different speed lets us assume that the same areas of vulnerability will be affected once more. For hundreds of thousands of years volcanoes have left their mark in the triangle of Gillenfeld – Strohn – Immerath, and this will recur again in the far distant future.
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