23 research outputs found
Rakkaudesta Venäjän rahvaaseen
Perhokalastajan pitkä marssi: Kuolasta Kamtsatkaan, Montaigne, Fen, Helsinki (2000
The role of ground frost, snow cover, ice break-up and flooding in the fluvial processes of the Oulanka river, NE Finland
Palaeohydrology of the rivers Ivalojoki and Oulankajoki, Finland
Reconstruction of the past is mainly based on work with 14 palaeochannels, 22 stratigraphical sections, 15 pollen diagrams, 43 radiocarbon dates and geomorphological mapping. Of the results revealed the most important are: low water balance of (1) the Boreal and (2) the Early Subboreal (around 4800 B.P.), (3) step‑wise inÂcrease in water balance approx. 2000 B.P. connected with intense activation in meander shifting. (4) continuing of this situation in the present form 1500–1600 B.P., and (5) the highest level of all in fluvial activity during the Little Ice Age. None of these features were affected by Man. Changes in post‑glacial fluvial activity are reflected, first of all, in the reverse trends of lateral and vertical channel movements. the last‑mentioned being strongly regulated by the isostatic land uplift. The dominance of the climatic factors over those of the glacio‑isostatic origin in controlling HoÂlocene fluvial work appears to increase the more the closer to the present day we come. These effects are to be seen in the activation of lateral shifting. The concentration of coarse lag deposits at the valley bottoms may have contributed in intensifying lateral movements in the near past. The research made calls for great methodological caution in palaeoÂhydrological interpretation of fluvial environments
Käsivarren luontoa suuren yleisön makuun : kirja-arvostelu
Suurtuntureiden luonto, Antero Järvinen ja Seppo Lahti, Helsinki (2004
Late-glacial and post-glacial development of the valleys Oulanka river basin, north-eastern Finland
The valleys of the Oulanka river and its tributaries, located in north eastern Finland, gained deep deposits of glaciofluvial drift during the last glacial retreat. The principal aim of this study is to date the deposiÂtion of these sediments, the prevailing conditions and the landforms created, and to trace post‑glacial changes in the relief of the area. The methods involved mapping of the valley floor landforms, grain‑size and stratigraphical analysis of these deposits, construction of profiles of the valleys and certain landforms by levelling, and sampling of minerogenic and organogenic horizons in the valley floor for pollen and diatom analysis and radiocarbon dating. Recent changes in relief were surveyed over the period 1975‑78. The majority of the glaciofluvial material was deposited proglacially around 9300‑9500 B.P. Initially the valleys themselves were flooded by water most probably having a direct outlet into the White Sea. The subsequent infilling of the valleys up to the prevailing water level then led to the accumulation of supra‑aquatic valley‑train deposits on top of the subaquatic delta formation. The valley‑train delta assumed more or less its present form immediately upon deposition in the lower reaches of the river valleys, but further upstream the final relief only emerged some centuries later, with the melting of the buried dead ice. The major role in the postglacial changes in relief is attributed to fluvial processes, regulated by isostatic land uplift. Downcutting was most rapid in the early post‑glacial period, declining later with the decreasing rate of land uplift. The dominant modern process is lateral erosion, although this is now restricted to only the lower reaches of the Oulanka river, where the meanders of the river are migrating downstream at varying speeds
Physical characteristics and palaeogeography of the Oulanka-Paanajärvi region on the Finnish-Karelian border
The paper has two aims. Firstly, it provides a review of basic physiographic features of the Kuusamo Uplands and its "pearl" the Oulanka-Paanajärvi area, to serve the needs of all the later articles in this volume. Secondly, based on the previous papers and author's observations in Russian Karelia, the course of the highest shoreline is presented for both sides of the Kuusamo watershed. This is the first up-to-date illustration of the ancient shores of the White Sea and the Baltic on the same map, a question which has remained unresolved for about a hundred years, mainly due to the location of the area on the border between the East and the West
Complexity of solar variability, hydrology and climatic conditions as evidenced in the case of the Oulujoki and Kemijoki river basins, Northern Finland
The work concentrates on the dependency relations between the sunspot numbers, mean annual temperatures, annual precipitation rates, mean annual discharges (MQ), mean discharges of the flood months and coinciÂdent monthly mean temperatures and winter precipitation figures on the basis of general trends, correlation coefficients and regression analysis results. All the dependency relations are examined using absolute values, and the first five also by reference to 5‑year moving means. With the excepÂtion of a few individual items, the information on the Oulujoki river basin reached as far back as 1896 and that on the Kemijoki river area to 1911. Attention was paid to the years before regulation of the flow of these rivers as well as to the whole observation period up to 1980 both when determining the correlation coefficients and in the regression analysis, where the disÂcharge rates were the dependent variables and other factors, individually and in varying combinations the independent variables. Even though in the preliminary comparison the 11‑year sunspot maxima seemed almost regularly to follow an exceptionally low discharge and vice versa, sunspots could not explain more than approx. 10 % of the changes in terms of absolute values. The situation altered completely upon transformation of the data to moving means, the explanatory power reaching 38.3 % at best, while in the case of the other factors the opposite trend was observed in the corresponding situation. This was taken as evidence of the fact that changes in sunspot numbers are revealed in meteorological and hydrological changes more distinctly over periods of more than one year, whereas, from the negative correlation between sunspot numbers and precipitation rates, attention was directed to a possible relation between solar and cyclonic activity. The various combinations of factors chosen to explain the hydrological changes reached an explanatory power of approx. 50 % at most