Geomorfoloske znacajke Otoka Visa

Abstract

Na temelju općih morfoloških i morfostrukturnih osobina moguće je determinirati nekoliko osnovnih dijelova otoka Visa: sjeverni, središnji i južni hrbat, te sjevernu i južnu udolinu, koji su izduženi u smjeru Z (ZJZ) – I (ISI). Morfološki najizraženiji su južna udolina (veća i gospodarski značajnija), koju velikim dijelom izgrađuju krška polja, te hrbat koji dominira središnjim dijelom otoka. Karbonatna osnova otoka Visa preoblikovana je tektonikom, a porast morske razine od oko 120 m nakon posljednjeg ledenog doba dao je otoku današnje konture. Ispucale karbonatne stijene izložene djelovanju klimatskih, bioloških i antropogenih procesa bile su temelj za oblikovanje krškog reljefa. Egzogeni destrukcijski (krški, fluvio-krški, derazijski i abrazijski) i akumulacijski procesi oblikovali su konačan izgled otoka kakav ima i danas. Materijal ispiran s padina ili erodiran djelovanjem paleo tekućica, akumuliran je u morfološkim depresijama u unutrašnjosti otoka, dok je uz obalnu liniju ispran ili djelovanjem valova preoblikovan u sedimente plaža. Znatna područja manje ili više strmih padina preoblikovana su antropogenim djelovanjem i to izgradnjom terasa za uzgoj vinove loze. Kao potporni element terasastih parcela služili su suhozidi, koji su imali funkciju zadržavanja tla na strmijim dijelovima padina. Danas je njihova funkcija bitno smanjena, pa su velike površine terasastih polja na padinama u zarastanju, a suhozidi se radi neodržavanja raspadaju.

[EN] On the basis of its general morphological and morphostructural characteristics it is possible to distinguish several parts of Vis island: northern, central and southern ridge and northern and southern valley, which are elongated in W (WSW) – E (ENE) direction. Morphologically, most prominent are the southern valley (bigger, built of karst poljes and economically more important) and ridge which dominates the central part of the island. Carbonate foundation of the Vis island is restructured by tectonics, and sea level rise of 120 m after the last ice age gave the island its recent contours. Cracked carbonate rocks, which were exposed to different climatic and biological processes, were the foundation of karst relief formation. Exogenous destructive and accumulative processes (karst, fluvio-karst, derasional and abrasional) have formed the final appearance of Vis island. The material which had been washed away from slopes or eroded by paleostreams activity accumulated in morphological depressions in interior part of the island, while along the coastline it was washed away or restructured as beach sediments by wave activity. Vast areas of more or less steep slopes were transformed by anthropogenic activity, or to be more precise, by terracing for grapevine cultivation. Dry stonewalls, which had the function of retention of the soil on the steeper parts of the slopes, served as a supporting element for terraced plots. Today, because of their greatly reduced function, vast areas of terraced poljes on hill-slopes are becoming overgrown and dry stonewalls are collapsing because they are not under maintenance anymore.