Lüneburg Kalkberg
Encyclopedia
The Lüneburg Kalkberg is the cap rock of a salt dome
in the western part of the German town of Lüneburg
. The Kalkberg was a gypsum
mine
during the middle ages
, but is today a Naturschutzgebiet
(nature reserve) and a common meeting place for city residents.
(calcium sulphate) and comes from sediments that were deposited there around 250 million years ago by the Zechstein Sea
. More recently (in geological terms), smaller disturbances have allowed the less dense Zechstein salts to flow together and force their way upwards into the younger, overlying rocks. Today these salts are near the earth's surface. Through this process, the more geologically-recent layers of rock around the rising mass of salt were deformed, shattered, and lifted; the initially horizontally-lying layers of salt were tilted and folded as they were rose upwards. Near the surface, the resulting salt dome
was leached
by groundwater
, so that only the less readily-soluble elements remained behind, such as carbonates and sulphates
. These are the compounds that make up the Kalkberg today, and can also be seen to protrude through the surface around Lüneburg.
Today, the rock walls only have very sparse vegetation, attracting animals and plants typical of dry grassland
habitats. On an area of 3.6 hectares (8.9 acre), one can find over 180 species of flowering plants, including several warmth-, light-, and chalk-loving types that otherwise grow only in south-central Europe. Several small caves are inhabited by bat
s.
, the castle on the Kalkberg was destroyed along with the nearby monastery.
The bulk of the Kalkberg has been quarried away over the centuries in order to use the gypsum as a building material. The former quarry is still recognizable from its steep, rugged walls. As a result of the depletion of the salt deposits and the increasing anhydrite
content of the gypsum, the quarry was closed in 1923. Of particular geological interest are deposits of boracite
and lüneburgite. Other minerals present include anhydrite
, calcite
, gypsum
, halite
, hematite
, hydroglauberite, jarosite
, kalistronite, lepidocrocite
, pyrite
, quartz
, sylvite
, syngenite and thenardite
.
The Kalkberg still has a height of 56.3 m above sea level. Originally it was about 80 m high. The Lüneburg surveyor Eduard Schlöbcke helped turn the Kalkberg into one of the first German nature reserves in 1932.
Salt dome
A salt dome is a type of structural dome formed when a thick bed of evaporite minerals found at depth intrudes vertically into surrounding rock strata, forming a diapir....
in the western part of the German town of Lüneburg
Lüneburg
Lüneburg is a town in the German state of Lower Saxony. It is located about southeast of fellow Hanseatic city Hamburg. It is part of the Hamburg Metropolitan Region, and one of Hamburg's inner suburbs...
. The Kalkberg was a gypsum
Gypsum
Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...
mine
Mine
Mine or mines can refer to:* Land mine, an anti-tank and anti-personnel weapon* Naval mine, an explosive device placed in water to destroy ships or submarines* Mining, extraction of mineral resources from the groundMine can also refer to:...
during the middle ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...
, but is today a Naturschutzgebiet
Naturschutzgebiet
A Naturschutzgebiet is a category of protected area within German Federal Conservation Law .- Points of law :...
(nature reserve) and a common meeting place for city residents.
Composition and Geology
The Kalkberg is made up largely of gypsumGypsum
Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...
(calcium sulphate) and comes from sediments that were deposited there around 250 million years ago by the Zechstein Sea
Zechstein
The Zechstein is a unit of sedimentary rock layers of Middle to Late Permian age located in the European Permian Basin which stretches from the east coast of England to northern Poland...
. More recently (in geological terms), smaller disturbances have allowed the less dense Zechstein salts to flow together and force their way upwards into the younger, overlying rocks. Today these salts are near the earth's surface. Through this process, the more geologically-recent layers of rock around the rising mass of salt were deformed, shattered, and lifted; the initially horizontally-lying layers of salt were tilted and folded as they were rose upwards. Near the surface, the resulting salt dome
Salt dome
A salt dome is a type of structural dome formed when a thick bed of evaporite minerals found at depth intrudes vertically into surrounding rock strata, forming a diapir....
was leached
Leaching (chemical science)
Leaching is the process of extracting minerals from a solid by dissolving them in a liquid, either in nature or through an industrial process. In the chemical processing industry, leaching has a variety of commercial applications, including separation of metal from ore using acid, and sugar from...
by groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
, so that only the less readily-soluble elements remained behind, such as carbonates and sulphates
Sulfate mineral
The sulfate minerals are a class of minerals which include the sulfate ion within their structure. The sulfate minerals occur commonly in primary evaporite depositional environments, as gangue minerals in hydrothermal veins and as secondary minerals in the oxidizing zone of sulfide mineral deposits...
. These are the compounds that make up the Kalkberg today, and can also be seen to protrude through the surface around Lüneburg.
Today, the rock walls only have very sparse vegetation, attracting animals and plants typical of dry grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...
habitats. On an area of 3.6 hectares (8.9 acre), one can find over 180 species of flowering plants, including several warmth-, light-, and chalk-loving types that otherwise grow only in south-central Europe. Several small caves are inhabited by bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...
s.
History
Until February 1371, a castle stood on top of the Kalkberg from where the Principality of Lüneburg-Brunswick was governed. During the Lüneburg War of SuccessionLüneburg War of Succession
The Lüneburg War of Succession was a conflict that broke out in 1370 in north Germany and lasted, with interruptions, for 18 years. The war was over the line of succession to the Principality of Lüneburg...
, the castle on the Kalkberg was destroyed along with the nearby monastery.
The bulk of the Kalkberg has been quarried away over the centuries in order to use the gypsum as a building material. The former quarry is still recognizable from its steep, rugged walls. As a result of the depletion of the salt deposits and the increasing anhydrite
Anhydrite
Anhydrite is a mineral – anhydrous calcium sulfate, CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the orthorhombic barium and strontium sulfates, as might be expected from the...
content of the gypsum, the quarry was closed in 1923. Of particular geological interest are deposits of boracite
Boracite
Boracite is a magnesium borate mineral with formula: Mg3B7O13Cl. It occurs as blue green, colorless, gray, yellow to white crystals in the orthorhombic - pyramidal crystal system. Boracite also shows pseudo-isometric cubical and octahedral forms. These are thought to be the result of transition...
and lüneburgite. Other minerals present include anhydrite
Anhydrite
Anhydrite is a mineral – anhydrous calcium sulfate, CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the orthorhombic barium and strontium sulfates, as might be expected from the...
, calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
, gypsum
Gypsum
Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...
, halite
Halite
Halite , commonly known as rock salt, is the mineral form of sodium chloride . Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pink, red, orange, yellow or gray depending on the amount and type of impurities...
, hematite
Hematite
Hematite, also spelled as haematite, is the mineral form of iron oxide , one of several iron oxides. Hematite crystallizes in the rhombohedral system, and it has the same crystal structure as ilmenite and corundum...
, hydroglauberite, jarosite
Jarosite
Jarosite is a basic hydrous sulfate of potassium and iron with a chemical formula of KFe3+362. This sulfate mineral is formed in ore deposits by the oxidation of iron sulfides...
, kalistronite, lepidocrocite
Lepidocrocite
Lepidocrocite , also called esmeraldite or hydrohematite, is an iron oxide-hydroxide mineral. Lepidocrocite has an orthorhombic crystal structure, a hardness of 5, specific gravity of 4, a submetallic luster and a yellow-brown streak. It is red to reddish brown and forms when iron-containing...
, pyrite
Pyrite
The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
, quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
, sylvite
Sylvite
Sylvite is potassium chloride in natural mineral form. It forms crystals in the isometric system very similar to normal rock salt, halite . The two are, in fact, isomorphous. Sylvite is colorless to white with shades of yellow and red due to inclusions. It has a Mohs hardness of 2.5 and a specific...
, syngenite and thenardite
Thenardite
Thenardite is an anhydrous sodium sulfate mineral, Na2SO4 which occurs in arid evaporite environments. It also occurs in dry caves and old mine workings as an efflorescence and as a crusty deposit around fumaroles. It occurs in volcanic caves on Mt...
.
The Kalkberg still has a height of 56.3 m above sea level. Originally it was about 80 m high. The Lüneburg surveyor Eduard Schlöbcke helped turn the Kalkberg into one of the first German nature reserves in 1932.
Sources
- Eduard Schlöbcke: Der Kalkbergführer. 1000 Jahre Kalkberg und Gipsbruch in Lüneburg. Lüneburg 1928
- Gerhard Stein: Der Lüneburger Kalkberg im Wandel der Zeiten. in: Jahrbuch Naturwiss. Verein Fürstentum Lüneburg, Bd. 39, 247-258, Lüneburg 1992
- Erhard Poßin: Der Kalkberg, Bd. 4 der Lüneburger Hefte Hrsg.: Backsteinprojekt e.V., Lüneburg, 2008