Presentation on theme: "Geopark Harz - Geodiversity and Geoconservation. 2-Days Excursion, 25-26 March, 2006: Karst area at the southern Harz rim (Karst walking trail) National."— Presentation transcript:
2-Days Excursion, 25-26 March, 2006: Karst area at the southern Harz rim (Karst walking trail) National Park Oberharz (High Harz)
Basics of the geology of the Harz Mountains Ore mining in the Harz and its ecological consequences
National Park Oberharz (High Harz) Visit of the historic silver mine “Grube Samson” in St. Andreasberg Attraction: the world's only surviving man-engine (“Fahrkunst”, a traditional- style lift)
National Park Oberharz (High Harz) The power of water: Exploitation of water resources during mining activities in the past One of the dozens of artificial lakes around Clausthal The problem of today: Acid mine drainages
Metal pollution in the Harz Heavy metal contamination of soils and water due to former mining activities Classification of soil units with respect to heavy-metal mobility Class I: locations without hazard to the environment. Class II: locations with a relatively low risk to the environment in the long-term. Class III: locations with low risk to the environment at present, but a hazard to the environment may arise under changing pH conditions. Class IV: locations that are a considerable hazard to the environment.
Acidification of soil and surface water („acid rain“) Surface water in equilibrium with the atmosphere has a pH of 5.7, due to the reaction with CO 2 (formation of carbonic acid). The primary emissions responsible for acid deposition are sulfur dioxide (SO 2 ) and oxides of nitrogen (NO x ) from the combustion of fossil fuels which are transformed and transported downwind before they are deposited. Acid rain is produced by the reaction of these gases in the atmosphere: SO 2 (g) + 2OH(g) --> H 2 SO 4 (aq) --> 2H + + SO 4 2- SO 2 (g) + H 2 O 2 (aq) --> H 2 SO 4 (aq) --> 2H + + SO 4 2- NO 2 (g) + OH(g) --> HNO 3 (aq) --> H + + NO 3 - During the smelting of sulphide-rich ores in the Harz, even as long ago as in the Middle Ages, substantial amounts of sulphur dioxide as well as heavy metals were released, which in part clearly exceed present-day levels. This resulted in a drastic acidification of soils and waters and high levels of tree deaths.
Acidification of soil and surface water („acid rain“) In the Harz region, the death of forests can also be attributed to the entry of pollutants from industrial areas and from traffic. Measures taken to alleviate the damage include the provision of lime in order to neutralize the acids which have accumulated, the reduction of the entry of pollutants, and the use of catalysts. Liming of a forest damaged by acid rain
Vegetation damages due to smelting and metal contamination and specially adapted flora on old mining dumps Vegetation damage area in the upper valley of the Innerste river near Clausthal Metal-resistant plant community “Armerietum halleri” and metal-resistant woodland at a Bronze age smelting site
Karst area at the southern Harz rim 200 million years ago, after the Zechstein sedimentation, the Harz Mountains rose and lifted up the horizontally deposited layers of the Zechstein era. Due to this process they are curved like a bowl and run inclined in the underground. On the surface you can only see a small band of all of this.
Karst area at the southern Harz rim A landscape created by the interaction of limestone, dolomite and gypsum from the Zechstein era with water Limestone consists of calcium carbonate (CaCO 3 ). Together with carbon dioxide it is soluble in water. The formula for the weathering and dissolution of limestone is CaCO 3 + CO 2 + H 2 O Ca(HCO 3 ) 2. The surface structures, which develop when limestone weathers are called karst. Calcite crystals Lime alga Limestone is a sedimentary rock. The largest limestone deposits formed on the seafloor, where calcite rich remnants of dead algae, mussels, snails, or corals accumulated in vast sedimentary layers. Afterwards they formed a rock under the high pressures of the overlying sediments.
Karst area at the southern Harz rim A landscape created by the interaction of limestone, dolomite and gypsum from the Zechstein era with water Dolomite is also a calcium-rich sedimentary rock, which contains magnesium in addition to calcium (CaMg(CO 3 ) 2 ). If limestone and dolomite experience high pressures and temperatures they form marble. Gypsum and anhydrite are not carbonates like limestone and dolomite but contain sulfate (CaSO 4 ). They are therefore salt rocks and are also soluble in CO 2 -rich water. gypsum crystals
Karst area at the southern Harz rim The surface structures which develop when limestone weathers are called karst. They are named after the “Kras” area in the southeastern part of the Slovenian Alps. Leached valleyPenetrated valleyDry valley SinkholeDolineUvala
Karst area at the southern Harz rim The solution of limestone rock takes place at the surface as well as underground. The dissolution of the limestone is due to acidified water standing in pools or running over the surface or in the underground and sculpting the rock. Disappearance of stream Karst springTear-off cleft Gypsum hump landscape Swelled knollCave
Karst area at the southern Harz rim Georisk karst Karst areas are often geologically risky places. Sudden seismic shocks can shake the ground or the ground collapses under one's feet. Cause for these shocks in the karst is the dissolution weathering. The Southern Harz gypsum karst landscape is a narrow belt extending through Lower Saxony, Thuringia and Saxony-Anhalt. The rocks there consists of very easily dissolving salts like salt rock and potassium salts, of a little more resistant gypsum and anhydrite and of limestone and dolomite.
Karst area at the southern Harz rim Karst features The surface of karst areas may be pitted with deep hollows. These dolines (small to medium sized enclosed depressions) act as funnels, collecting rainwater and leading it underground into cave systems. Doline in karst area Surface leaching features (flutings or grooves) in a karst area
Karst area at the southern Harz rim Reef formation in the Zechstein ocean: During the Zechstein era, the Harz area was located at 30°N and the climate was tropical and warm. The shallow sea allowed the extensive growth of reef-forming organisms and deposition of limestone. A 240 million-year-old tropical reef: “Westersteine” formed by stromatolithes (algae mats) A 240 million-year-old tropical reef: Quarry giving insight into the marine deposition of greywacke and dolomite formed from reef debris
Karst area at the southern Harz rim A landscape created by the interaction of limestone, dolomite and gypsum from the Zechstein era with water Karst springs: Rhume spring, one of the largest karst springs in Europe Dolines, holes and caves (subrosion): The gypsum karst landscape at the Hainholz nature reserve
Karst area at the southern Harz rim A landscape created by the interaction of limestone, dolomite and gypsum from the Zechstein era with water Caves created by water and CO 2 : Einhornhöhle (“Unicorn” cave) in dolomite; tour by Dr. R. Nielbock (geology, excavations) Natural caves used by animals and early man since the stone age: Cultural heritage Steinkirche (“Rock church”)
Karst area at the southern Harz rim The gypsum karst and its vegetation The steep and variable relief in the southern Harz Mountains did not allow farming or settlements in many places. Many of the typical beech forests are therefore, untouched by humans and extremely rich in animal and plant species. More than 400 types of mushrooms some of which are only found here in Germany have been proven to exist here. Shallow soils on top of gypsum and dolomites have been used for sheep and goat farming for centuries. In these areas flora and fauna from southeastern Europe could spread, including orchids and gentian. Typical dry meadow in karst area with special vegetation Rare fern growing in the humid microclimate of sinkholes and dolines
Karst area at the southern Harz rim Unfortunately, more and more of this landscape is being destroyed; in many places dolomite and gypsum is quarried by globally operating business groups. Healing wounds in a gypsum quarry: Renaturation at the “Oberer Kranichteich” near Neuhof Gypsum mining at near Osterode
Geoparks GEOPARKS - A NEW INITIATIVE Until recently, no international convention on geological heritage was existing. The initiative to support national Geoparks responds to the strong need expressed by the geoscientific community in numerous countries for an international framework of geoconservation, to enhance the value of the heritage of the Earth, its landscapes and geological formations, that are key witnesses to the history of life on Earth. The Geopark concept was developed by several sources, mainly European ones, in strong cooperation with UNESCO. WHAT IS A GEOPARK? A Geoparks is a territory with well-defined limits that has a large enough surface area for it to serve local economic development (mainly through tourism). The Geopark comprises a number of geological heritage sites of special scientific importance, rarity or beauty. These features are representative of a region's geological history and the events and processes that formed it.
Geoparks 33 National Geoparks in Europe and China (thereinto, 9 geoparks are new members *) were evaluated and are at the moment members of the Global Network of Geoparks assisted by UNESCO. Geoparks in Europe
Geopark Harz The Geopark Harz- Braunschweiger Land- Ostfalen was recently acknowledged by the UNESCO and is now officially affiliated into the "Global UNESCO Network of Geoparks” by the cultural organization of the United Nations. Geopark Harz - Braunschweiger Land- Ostfalen