permafrost
per·ma·frost
P0199600 (pûr′mə-frôst′, -frŏst′)permafrost
(ˈpɜːməˌfrɒst)per•ma•frost
(ˈpɜr məˌfrɔst, -ˌfrɒst)n.
per·ma·frost
(pûr′mə-frôst′)permafrost
permafrost
| Noun | 1. |  permafrost - ground that is permanently frozen |
| 单词 | permafrost | |||
| 释义 | permafrostper·ma·frostP0199600 (pûr′mə-frôst′, -frŏst′)permafrost(ˈpɜːməˌfrɒst)per•ma•frost(ˈpɜr məˌfrɔst, -ˌfrɒst)n. per·ma·frost(pûr′mə-frôst′)permafrostpermafrost
permafrostpermafrost,permanently frozen soil, subsoil, or other deposit, characteristic of arctic and some subarctic regions; similar conditions are also found at very high altitudes in mountain ranges. In 1962 measurements in a borehole drilled on Melville Island, Northwest Territories, Canada, showed that the ground was frozen to a depth of at least 1,475 ft (450 m); comparable thicknesses have been found in other far north regions. Tundrastundra, treeless plains of N North America and N Eurasia, lying principally along the Arctic Circle, on the coasts and islands of the Arctic Ocean, and to the north of the coniferous forest belt. ..... Click the link for more information. , though underlaid by permafrost, today support centers of population in Alaska, Canada, and Siberia. Permafrost is a very fragile system that may easily be damaged or destroyed by the presence of human-generated heat. A controversy developed in the late 1960s and early 70s over the construction of an oil pipeline from the Alaska North Slope to the southern part of the state. Critics of the project argued that if the pipeline containing hot oil ever came into contact with the permafrost, it would melt the permafrost; the pipeline would then sink and eventually break. The oil spilled during the breakage would result in a major ecological disaster. It was decided to build the pipeline with insulated pipe raised above the permafrost or on gravel beds in order to prevent melting and thus preserve both the pipeline and the ecosystem. Permafrosta vague term of many meanings applied to the phenomenon of the cooling of rocks on the upper part of the earth’s crust to temperatures of zero and below; the rocks themselves that have hardened as a result of the freezing of the moisture they contained; and the stratum (layer) or zone (region of horizontal spread) of rocks that do not thaw for a long time. The term “permafrost” was introduced into scientific usage in 1927 by the founder of the school of Soviet geocryologists, M. I. Sumgin, who defined it as ground frost that exists for two to several thousand years. The phrase “ground frost” was not clearly defined in this formulation, and this led to the use of permafrost in various meanings. As geocryology developed, investigators found themselves increasingly inconvenienced by the word “permafrost,” and as a result it was sharply criticized by P. F. Shevtsov, L. A. Meister, and others in the 1950’s at the V. A. Obruchev Institute of Geocryology of the Academy of Sciences of the USSR. This led to a prolonged discussion of all geocryological terminology. Of the many scientific terms suggested to replace “permafrost,” “perennial frozen rocks” and “perennial cryolithozone” are in widest use. REFERENCESOsnovy geokriologii (merzlotovedeniia), parts 1-2. Moscow, 1959.Materialy po obshchemu merzlotovedeniiu. Moscow, 1959. Popov, A. I. Merzlotnye iavleniia v zemnoi kore (kriolitologiia). Moscow, 1967. Dostovalov, B. N., and V. A. Kudriavtsev. Obshchee merzlotovedenie. Moscow, 1967. A. E. SNOPKOV permafrost[′pər·mə‚frȯst]permafrostpermafrostpermafrostpermafrostpermanently frozen ground on which only a thin layer thaws in the summer, as in the high Arctic and Antarctic.permafrost
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