Regelation

Regelation

Regelation is the phenomenon of melting under pressure and freezing again when the pressure is reduced. Many textbooks and websites claim that "regelation can be demonstrated by looping a fine wire around a block of ice and attaching a heavy weight to it. The pressure exerted on the ice slowly melts it locally, permitting the wire to pass through the entire block. The wire's track will refill as soon as pressure is relieved, so the ice block will remain solid even after wire passes completely through." This experiment is possible for ice at –10 °C or cooler. It has also been suggested that the heating of the wire under pressure and tension may also play a role. [ [http://www.scienceyear.com/about_sy/index.html?page=/about_sy/news/ps_76-100/ps_issue92.html Planet Science | About ] ]

If 1 mm diameter wire is used, over an ice cube 50 mm wide, the area the force is exerted on is 50 mm2. This is 50 x 10-6 m2.
Force (in newtons) equals pressure (in pascals) multiplied by area (in square metres).
If at least 500 atm (50 MPa) is required to melt the ice, a force of (50×106 Pa)(50×10-6 m2) = 2500 N is required, a force roughly equal to the weight of 250 kg on Earth.

Regelation was discovered by Michael Faraday. Regelation occurs only for substances, such as ice, that have the property of expanding upon freezing, for the melting points of those substances decrease with increasing external pressure. The melting point of ice falls by 0.0072 °C for each additional atm of pressure applied. For example, a pressure of 500 atmospheres is needed for ice to melt at –4 °C. [http://amsglossary.allenpress.com/glossary/search?id=regelation1 Glossary of Meteorology: Regelation] , American Meteorological Society, 2000]

Examples of Regelation

*A glacier can exert a sufficient amount of pressure on its lower surface to lower the melting point of its ice. The melting of the ice at the glacier's base allows it to move from a higher elevation to a lower elevation. Liquid water may flow from the base of a glacier at lower elevations when the temperature of the air is above the freezing point of water.

Notes


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Look at other dictionaries:

  • Regelation — Re ge*la tion ( l? sh?n), n. [Pref. re + L. gelatio a freezing.] (Physics) The act or process of freezing anew, or together,as two pieces of ice. [1913 Webster] Note: Two pieces of ice at (or even) 32? Fahrenheit, with moist surfaces, placed in… …   The Collaborative International Dictionary of English

  • Regelation — Regelation, s. Eis, S. 473 …   Meyers Großes Konversations-Lexikon

  • Regelation — Regelatiōn (lat.), das Zusammenfrieren aneinander gedrückter Eisstücke …   Kleines Konversations-Lexikon

  • regelation — [rē΄jə lā′shən] n. [see RE & GELATION1] a freezing or refreezing together of pieces of ice after a pressure, which has caused melting at a temperature below the normal melting point, has been removed regelate [rē΄jə′lāt΄] vi. regelated,… …   English World dictionary

  • Regelation — Unter Regelation versteht man die Druckabhängigkeit des Phasenübergangs zwischen festem und flüssigem Aggregatzustand bei Stoffen, deren Schmelze eine höhere Dichte aufweist als ihre feste Phase. Die Regelation bewirkt die Verflüssigung des Eises …   Deutsch Wikipedia

  • Regelation — Re|ge|la|ti|on 〈f. 20〉 Umwandlung von Wasser in Eis bei niedrigen Temperaturen u. einer plötzlichen Abnahme des Drucks, unter dem es vorher (wegen des gegenüber Eis geringeren Volumens) flüssig war, verantwortlich für das Fließen von Gletschern u …   Universal-Lexikon

  • regélation — (re jé la sion) s. f. Synonyme de REGEL. SUPPLÉMENT AU DICTIONNAIRE    REGÉLATION. Ajoutez : •   Il se passe ici, dit M. Dumas, ce que l on remarque dans le phénomène de la regélation, si bien signalé par Faraday : les petits glaçons se fondent… …   Dictionnaire de la Langue Française d'Émile Littré

  • regelation — /ree jeuh lay sheuhn/, n. Physics. a phenomenon in which the freezing point of water is lowered by the application of pressure; the melting and refreezing of ice, at constant temperature, caused by varying the pressure. [1855 60; RE + GELATION] * …   Universalium

  • regelation — noun The fusion of two pieces of ice by pressure (which lowers its freezing point) …   Wiktionary

  • regelation —   the refreezing of water into ice after pressure which caused it to melt is released …   Geography glossary

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