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fil. dr. ANDERS RAPP 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):95-99
Rapp, Anders: Periglacial nivation cirques and local glaciations in the rock canyons of Söderåsen, Scania, Sweden. A discussion and new interpretation. Geografisk Tidsskrift 82: 95–99, Copenhagen, October 15, 1982. Present opinions about the genesis of the rock canyons OdensjOn, Skäralid and Klöva Hallar of Söderåsen, Sweden are reviewed, and a new theory is presented. It is proposed, that during periglacial tundra periods large amounts of drifting snow collected in valleys of north-south directions. Small glaciers were created, which caused local overdeepening and removal of loose material. These processes were active in tundra periods before and after the main Quaternary glaciations. SUMMARY Odensjön, Skäralid and Klöva Hallar are three valleys of canyon type, deeply cut (60–100 m) into the horst block of Söderåsen, of fractured Precambrian gneiss rock. It has been shown by other authors that the cold periods after the Weichselian deglaciation were characterized by permafrost and ice wedges on sandy plains in south Sweden. Strong winds caused widespread wind-polishing of stones and bedrock, predominantly from easterly and westerly directions. Based on this evidence, the author presents the theory that large deposits of wind-blown snow were trapped in the canyon valleys of Söderåsen, except for the valleys of east-west directions. The snow was metamorphosed to firn and local, small glaciers, which filled the valleys. The rims of the canyon valleys have in many cases well developed nivation hollows, either steep nivation funnels or gently sloping, semicircular nivation cirques. Odensjøn is a closed, semicircular rock basin, which has been much discussed by scientists earlier, and which seems to fit the theory of creation by nivation from mainly west, but also east, and a local cirque glacier flow northwards causing the overdeepening and removal of loose material. The three valleys mentioned were problably widened and deepened into a series of nivation basins in tundra periods before and after each major continental glaciation. The nivation hollows and the deep canyon valleys were not destroyed by glacial erosion during the Weichselian and earlier Quaternary major ice advances, because the valleys were filled with densely packed snow and ice from snow drifting before the main glacier front moved over them from NE directions. The theory will be further checked by a team of scientists from the Department of Physical Geography in Lund. A comparison is made with cirque forms in present-day mountain tundra conditions in the area of Kärkevagge in northern Lappland, investigated by the author during the 1950's and later. 相似文献
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城市居民购房与租房的居住选择倾向及其机制存在差异,但当前对租房方面的研究仍显不足。鉴于此,本文构建城市租房户居住选择过程中“好房子、好位置、低租金”不可兼得的“不可能三角”理论框架及其基本理论模型,这为研究租房户居住选择倾向提供了一个新的视角。以广州都市区1328个社区为案例,得出广州都市区的租房户比例呈现核心区低,中心城区和近郊区较高的空间分异格局,并呈现显著的空间关联特征。构建广州都市区租房户居住选择倾向因素指标体系,该体系由租金水平、住房自身条件和区位条件三大类9个指标构成。通过空间误差模型分析表明,广州都市区租房户倾向于居住在低租金水平和房龄较新的社区,且被动选择租住在住房建筑面积较小、住房内部设施较差、日常生活便利性较差的社区中。该结论可丰富和完善中国特大城市居民租房选择理论,为特大城市租赁住房政策制定提供决策参考。 相似文献
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