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20-577: The municipality lies on a plateau in the southern Volcanic Eifel at the northern edge of the Kondelwald forest. The municipal area is 58.4% wooded. Hontheim belongs to the Verbandsgemeinde of Traben-Trarbach . Hontheim's Ortsteile , besides the main centre, are Wispelt, Krinkhof and Bonsbeuern. Beginning in 1794, Hontheim lay under French rule. In 1814 it was assigned to the Kingdom of Prussia at

40-557: A cross gules and gules a hound courant of the first. Through the municipality runs Bundesstraße 421. To the west runs the Autobahn A ;1 . In Ürzig is a railway station on the Koblenz-Trier railway line. The state spa town of Bad Bertrich , with Germany's only Glauber's salt (sodium sulphate decahydrate; Na 2 SO 4 •10H 2 O) hot spring , is only 3 km away. This Bernkastel-Wittlich location article

60-463: A diverse landscape that clearly witnesses to very recent events in geological terms. The entire Volcanic Eifel covers an area of about 2,000 km (770 sq mi) and as of 2007 has a population of about 200,000. The following volcanoes belong to the Eifel, sorted by height in metres (m) above sea level ( Normalhöhennull , NHN) : Of particular note is the volcanic caldera known as Laacher See ,

80-602: A mineral or fragments of rock are hand-selected for analysis. These are then irradiated to produce Ar from K via the (n-p) reaction K(n,p) Ar. The sample is then degassed in a high-vacuum mass spectrometer via a laser or resistance furnace. Heating causes the crystal structure of the mineral (or minerals) to degrade, and, as the sample melts, trapped gases are released. The gas may include atmospheric gases, such as carbon dioxide, water, nitrogen, and radiogenic gases like argon and helium, generated from regular radioactive decay over geologic time. The abundance of Ar* increases with

100-572: A rock retains all of its Ar after cooling past the closing temperature and that this was properly sampled during analysis. This technique allows the errors involved in K-Ar dating to be checked. Argon–argon dating has the advantage of not requiring determinations of potassium. Modern methods of analysis allow individual regions of crystals to be investigated. This method is important as it allows crystals forming and cooling during different events to be identified. One problem with argon-argon dating has been

120-466: A sample of known age for a standard. Because this (primary) standard ultimately cannot be determined by Ar/ Ar, it must be first determined by another dating method. The method most commonly used to date the primary standard is the conventional K/Ar technique . An alternative method of calibrating the used standard is astronomical tuning (also known as orbital tuning ), which arrives at a slightly different age. The primary use for Ar/ Ar geochronology

140-460: A single measurement of argon isotopes . Ar/ Ar dating relies on neutron irradiation from a nuclear reactor to convert a stable form of potassium ( K) into the radioactive Ar. As long as a standard of known age is co-irradiated with unknown samples, it is possible to use a single measurement of argon isotopes to calculate the K/ Ar* ratio, and thus to calculate the age of the unknown sample. Ar* refers to

160-707: Is a stub . You can help Misplaced Pages by expanding it . Volcanic Eifel The Volcanic Eifel or Vulkan Eifel ( German : Vulkaneifel ), also known as the East Eifel Volcanic Field ( EEVF ), is a region in the Eifel Mountains in Germany that is defined to a large extent by its volcanic geological history. Characteristic of this volcanic field are its typical explosion crater lakes or maars , and numerous other signs of volcanic activity such as volcanic tuffs , lava streams and volcanic craters like

180-401: Is dating metamorphic and igneous minerals. Ar/ Ar is unlikely to provide the age of intrusions of granite as the age typically reflects the time when a mineral cooled through its closure temperature . However, in a metamorphic rock that has not exceeded its closure temperature the age likely dates the crystallization of the mineral. Dating of movement on fault systems is also possible with

200-506: Is the Ar*/ Ar ratio. The J factor relates to the fluence of the neutron bombardment during the irradiation process; a denser flow of neutron particles will convert more atoms of K to Ar than a less dense one. The Ar/ Ar method only measures relative dates. In order for an age to be calculated by the Ar/ Ar technique, the J parameter must be determined by irradiating the unknown sample along with

220-439: Is thought that future eruptions may occur in the Eifel, as: In 2020, Professor Kreemer noted that Eifel was the only region within an area of Europe studied where ground motion happened at significantly higher levels than expected. It is possible that such movements originate from a rising magma plume . This activity does not imply an immediate eruptive danger, but might suggest an increase in volcanic and seismic activity in

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240-429: The Ar/ Ar method. Different minerals have different closure temperatures; biotite is ~300°C, muscovite is about 400°C and hornblende has a closure temperature of ~550°C. Thus, a granite containing all three minerals will record three different "ages" of emplacement as it cools down through these closure temperatures. Thus, although a crystallization age is not recorded, the information is still useful in constructing

260-489: The Congress of Vienna . Since 1947, it has been part of the then newly founded state of Rhineland-Palatinate . The council is made up of 12 council members, who were elected by proportional representation at the municipal election held on 7 June 2009, and the honorary mayor as chairwoman. The municipal election held on 7 June 2009 yielded the following results: The municipality's arms might be described thus: Per fess Or

280-774: The Laacher See . The Volcanic Eifel is still volcanically active today. One sign of this activity is the escaping gases in the Laacher See. The Volcanic Eifel stretches from the Rhine to the Wittlich Depression . It is bordered in the south and southwest by the South Eifel , in the west by Luxembourg and Belgian Ardennes and in the north by the North Eifel including the Hohes Venn . To

300-455: The radiogenic Ar, i.e. the Ar produced from radioactive decay of K. Ar* does not include atmospheric argon adsorbed to the surface or inherited through diffusion and its calculated value is derived from measuring the Ar (which is assumed to be of atmospheric origin) and assuming that Ar is found in a constant ratio to Ar in atmospheric gases. The sample is generally crushed and single crystals of

320-458: The age of the sample, though the rate of increase decays exponentially with the half-life of K, which is 1.248 billion years. The age of a sample is given by the age equation: where λ is the radioactive decay constant of K (approximately 5.5 x 10 year , corresponding to a half-life of approximately 1.25 billion years), J is the J-factor (parameter associated with the irradiation process), and R

340-585: The east the Rhine forms its geographical boundary, with no volcanicity immediately beyond it. The Volcanic Eifel is divided into three natural regions: The centre of the Volcanic Eifel is the region around Daun and Manderscheid and the areas within the Mayen-Koblenz district . The landscape of the Volcanic Eifel is dominated by recent volcanism. Volcanic craters, thick pumice and basalt layers and maars create

360-461: The region. 50°17′N 7°00′E  /  50.283°N 7.000°E  / 50.283; 7.000 Argon-argon dating Argon–argon (or Ar/ Ar ) dating is a radiometric dating method invented to supersede potassium–argon (K/Ar) dating in accuracy. The older method required splitting samples into two for separate potassium and argon measurements, while the newer method requires only one rock fragment or mineral grain and uses

380-479: The site of an eruption around 12,900 years ago that had an estimated VEI of 6. The tephras deposited by past eruptions of the Volcanic Eifel are lithological deposits that are radiometrically dateable via argon-argon dating of K-feldspar grains. These have in turn been utilised to ascertain the ages of climatic changes such as transitions from glacial to interglacial states during the Pleistocene . There

400-428: The thermal history of the rock. Dating minerals may provide age information on a rock, but assumptions must be made. Minerals usually only record the last time they cooled down below the closure temperature, and this may not represent all of the events which the rock has undergone, and may not match the age of intrusion. Thus, discretion and interpretation of age dating is essential. Ar/ Ar geochronology assumes that

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