LANDSCAPE DIFFERENTIATION AND DEVELOPMENT OF THE SOUTH-EASTERN S0RKAPP LAND, SPITSBERGEN

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1 Wiesław Ziaja Institute of Geography Jagiellonian University Kraków, Poland X X Polar Symposium Lublin, 1993 LANDSCAPE DIFFERENTIATION AND DEVELOPMENT OF THE SOUTH-EASTERN S0RKAPP LAND, SPITSBERGEN INTRODUCTION The aim of work is to present an unusually interesting, natural landscape of the south eastern Sorkapp Land. The landscape is very differentiated there, in a comparatively small area, and undergoes extremely quick development, even in the scale of Svalbard. The area has been precisely recognized owing to terrain mapping of basic geocomplexes in the scale 1: in The analysis of results of that mapping made possible the distinction of 10 landscape units, strictly different each from others, described shortly below (Fig. 1). Clear traces of the landscape development, in the period since the Little Ice Age at least, are preserved in each of those units. Landscape changes during the 20th century are also visible owing to the comparison of the contemporary landscape (according to: results of terrain mapping, infrared air photos 1:50000 from 1990 and satellite Landsat" pictures from 1985, from Norsk Polarinstitutt in Oslo) with the landscape from 1936 shown in the topographical map 1: (used till now because of lack of a new one) and from 1961 shown in standard air photos 1: SPATIAL REVIEW Basic features of the contemporary landscape and the environmental changes which resulted that landscape are described within the following units (Fig. 1): 1. Keilhaubreen and the marginal zone of that glacier. The glacier reached the sea in 1936 in the line of the contemporary coast (more or less). The glacier has retreated ca. 2 km since 1936 disappearing from 7 km 2, i.e. from more than the contemporary area of that glacier. A slightly undulated plain, covered with a thin layer of moraine (W ójcik, Ziaja, in print), is modelled intensively by glacial rivers and, at the edge, by the sea. So the landscape has been completely changed there during the short time of a few dozen years. That time was sufficient for 479

2 development of a vegetation which is so dense that it is visible in the infrared photos. 2. The outwash plain at the foot of Svartkuven. The plain has been terraced once. That is evidenced by remains of the marine terraces sticking out up to 1 m from under outwash material. Reshaping of the plain had to be intensified during the last few centuries. Remains of huts, which are supposed to be not older the 17th century, have been covered partly with outwash material. Lack of a vegetation evidences the continuity of the process of burying the plain. 3. Skoltsletta the terraced coastal plain. The rate of landscape development is there the smallest in all plain areas. The preserved marine terraces area is modelled slowly by a complex of morphogenetic processes. That does not refer to the banks of the glacial river flowing across the plain and to the sea coast in the northern part of the plain, which undergo comparatively quick reshaping. Landscape stability of that unit is the biggest in the described area. This is also evidenced by the vegetation, quite dense in places. 4. The young, accumulative coastal plain of Betty bukta. It is up to 130 m wide, with a big quantity of driftwood. There have been situated the huts mentioned above in the old" coast of that gulf. Hence the rate of increasing the land may be estimated at m (of width) per 100 years. There is a clear (lm) depression between the old coast with the remains of huts and the high contemporary coastal ridge. That testifies the thesis that the marine accumulation during the 17-19th centuries was smaller than now. A plant succesion, going from the land side, is very slow there. 5. Svartkuven, 421 m a.s.l. That mountainous massif undergoes intensive sheet wash first of all because of a small resistance of the bedrock (shales and mudstones). Hence there is a complete lack of vegetation. The area of slopes free of glaciers has increased considerably because of a big reduction of thickness of the glaciers during the 20th century. 6. Dumskolten, 624 m a.s.l. That steep mountain is built of the more resistant bedrock (sandstone layers in the upper parts) than Svartkuven, and because of that modelled mainly by gravitational falling (creeping) and line erosion in numerous furrows. The slow accumulation has place at the foots of those furrows within the ejection cones. Those cones are mature, which is evidence by the densest vegetation in the SE Sorkapp Land. Bigger landscape changes were not noticed there, apart from deglaciation of the western and northern slopes connected with the reduction of thickness of the glaciers during the 20th century. 7. Skolthuken, 309 m a.s.l. That small mountain undergoes marine abrasion (and gravitational falling and creeping) from the sea side. There is a complete lack of a vegetation there. However the structural top flattening with preserved single marine gravels evidences the lack of bigger landscape changes there since the Little Ice Age at least. 8. The marginal zone of Svartkuvbreen, Dumskolten and the adjacent 480

3 glaciers. The majority of that unit was under the glaciers in Istoppane and Rundtuva were nunataks at that time. But only the north-western slopes of them are glaciated today. Of course, in a much smaller degree, because of the reduction of thickness of the glaciers. Hence bare rocky slopes and ice cored moraines dominate there. The Dumskoltbreen exposed to SSW has been diminished 4-5 times, and the Svartkuvbreen exposed to NE 2-3 times only, in spite of that the first one is situated much higher. That evidences that exposure influences glaciation much more than height a.s.l. there. A complete lack of plants is a sign of landscape instability. 9. Randbreen and the marginal zone of that glacier. The glacier had a partly tide-water front in 1936 (Lefauconnier and Hagen 1991) and has retreated km since that time. That made possible to uncover the rocky basements of the raised marine terraces (conditioned structurally) after removing marine Quaternary deposits out of them. The unit, covered with morainic material thick up to a few m apart from rocky edges, undergoes reshaping by a few glacial streams. Single plants are a sign of beginning succession near the marine cliff. 10. Randberget, 305 m a.s.l. That is a steep questa from the sea side and a comparatively gentle slope from the land, glaciated side. The glacier, reaching the sea in the narrow valley dividing the ridge of Randberget in 1936, has retreated 0.4 km since that time. Lower parts of slopes (from the land side) were deglaciated simultaneously because of lessening of the thickness of ice at 50 m at least. First single plants have appeared on those slopes. But the steep walls from the sea side have the richest animal life in the described area, in the form of small bird colonies. RECAPITULATION The most rapid landscape changes have place in the marginal zones of glaciers retreating since the maximum extent in the Little Ice Age. That retreat was particularly big during the last 50 years. It is worth of notice that stabilizing of the landscape after deglaciation is the quicker, the lower a.s.l. an area is situated. The most important stabilizing properties are: increasing density of a vegetation and creating a constant net of surface waters. As far as that stabilizing is concerned the landscape of the unit No. 1 is the most developed. From the other side, the unit No. 8 the highest one of the marginal zones is just after deglaciation but before a new equilibrium. The landscape of the coastal plains is the most changeable near the coast when marine accumulation or erosion created or wasted big fragments of the land during years (the landscape unit No. 4). The higher situation of plain fragments, the slower are landscape changes. They are influenced by the rate and way of denudation of the slopes of the adjacent mountains. The less resistant are 481

4 the bedrock of those mountains, the quicker are the denudation of them and the covering up of the plains with deposits. In the mountainous massifs landscape development is the quicker, the more parts of their foots are glaciated or eroded by the sea. The height of the massifs does not influence the rate of their landscape development in the described area. Hence the highest massif, Dumskolten, has been changed in the smallest degree during the 20th century. From the other side, that massif has the most diversified landscape because of the biggest drop. The terrain investigations for that work were done within the project financed by the Ministry of National Education. REFERENCES Lefauconnier B. and Hagen J. O. 1991: Surging and calving glaciers in eastern Svalbard. Meddelelser Nr. 116, Norge Topografisk kart over Svalbard 1: , Blad CI 3, Seirkapp. Norsk Polarinstitutt, Oslo. Wójcik A. and Ziaja W. (in print): Relief and Quaternary of the southern Sorkapp Land, Spitsbergen. Polish Polar Research. Address of the author: dr Wiesław Ziaja, Institute of Geography, Jagiellonian University, Grodzka 64, Kraków, Poland ZRÓŻNICOWANIE I EWOLUCJA KRAJOBRAZU POŁUDNIOWO-WSCHODNIEGO S0RKAPPLANDU, SPITSBERGEN Streszczenie Celem pracy jest przedstawienie szybkiej ewolucji mocno zróżnicowanego krajobrazu obszaru wymienionego w tytule. Wnikliwe poznanie tego obszaru nastąpiło dzięki kartowaniu terenowemu geokompleksów w skali 1: w lecie 1991 r. Analizując wyniki kartowania wydzielono 10 jednostek krajobrazowych jednolitych wewnętrznie, a zdecydowanie różnych od siebie, wymienionych niżej. W każdej z nich zachowały się wyraźne ślady ewolucji krajobrazu w okresie co najmniej od małej epoki lodowej. Ewolucja ta w ciągu XX w. jest widoczna również dzięki porównaniu krajobrazu współczesnego (wg wyników kartowania oraz zdjęć lotniczych w podczerwieni 1:50000 z 1990 r. i obrazów satelitarnych Landsat" z 1985 г., z Norsk Polarinstitutt w Oslo) z tym co przedstawia mapa topograficzna 1: wg stanu z 1936 r. (wciąż używana z braku nowszej) oraz zdjęcia lotnicze zwykłe 1: z 1961 r. W pełnym tekście pracy podstawowe cechy krajobrazu współczesnego i jego ewolucję opisano w obrębie następujących jednostek (rye. 1): 1. Lodowiec Keilhaubreen i jego strefa marginalna. 2. Nadmorska nizina napływowa u podnóży Svartkuven. 3. Skoltsletta sterasowana równina nadmorska. 4. Młode akumulacyjne wybrzeże Bettybukta. 5. Svartkuven, masyw górski, 421 m n.p.m. 6. Dumskolten, masyw górski, 624 m n.p.m. 482

5 7. Skolthuken, masyw górski, 309 m n.p.m. 8. Strefa marginalna lodowców Svartkuvbreen, Dumskoltbreen i sąsiednich. 9. Lodowiec Randbreen i jego strefa marginalna. 10. Randberget, grzbiet górski, 305 m n.p.m. Najszybsze zmiany krajobrazu zachodzą w strefach marginalnych lodowców cofających się od zasięgu maksymalnego w małej epoce lodowej. W ciągu ostatniego półwiecza proces ten był szczególnie nasilony. Warto zauważyć, że po deglacjacji stabilizacja nowego krajobrazu zachodzi tym szybciej, im mniejsza jest wysokość n.p.m. Stabilizacja ta wyraża się m. in. wzrostem gęstości szaty roślinnej oraz powstawaniem trwałej sieci wód powierzchniowych. Pod tym względem przoduje tutaj strefa marginalna Keilhaubreen. Krajobraz nizin nadmorskich zmienia się najszybciej w strefie przybrzeżnej, gdzie akumulacja lub erozja morska utworzyły lub zniszczyły duże fragmenty lądu w ciągu ostatnich lat (nad Bettybukta). Wyżej zmiany następują wolniej i są uzależnione od tempa i sposobu denudacji stoków sąsiednich gór. Im mniej odporne jest podłoże tych gór, tym szybciej następuje denudacja i zasypywanie nizin, na co wskazuje porównanie ww. jednostek nr 2 i 3. W masywach górskich ewolucja krajobrazu jest tym szybsza, im mniej odporne jest ich podłoże oraz im większa część ich stoków jest zlodowacona lub podcinana przez morze. Na opisywanym obszarze wysokość gór nie wpływa istotnie na szybkość ewolucji ich krajobrazu. Dlatego np. najwyższy masyw, Dumskolten, został najmniej przekształcony w czasie obecnego stulecia. Przy tym jest on, właśnie na skutek największej deniwelacji, najbardziej zróżnicowany krajobrazowo. 483

6 Fig. ł. South-eastern Sorkapp Land, Spitsbergen. Landscape units 1-10: explanations in the text. Signatures: 1 contemporary extent of the glaciation, 2 extent of the glaciation in 1936, 3 glacial moraines from the Little Ice Age, 4 boundaries of the landscape units which are not the extents of the contemporary glaciation. 484