Doline Morphogenetic Processes from Global and Local Viewpoints

Povzetek

Geomorfogenetski procesi korozijskih vrtač so razpoznavni iz omejitev za njihovo globalno in lokalno razprostranjenost: več padavin kot znaša potencialna evapotranspiracija, prepustna odeja prsti, kraška vodna gladina in korozijska fronta (to je stik agresivne in sigotvorne vode) globlje pod površjem, površinski naklon pod 30°, kompaktna kamnina. Vrtače so posledica lokalno pospešene korozije. Njihov začetek je v lokalno bolj pretrti kamnini z večjo specifično (površina/volumen) površino, izpostavljeno koroziji talne vlage. Vpliv zdrobljenosti kamnine je bil potrjen z laboratorijskim poskusom. Poznejša rast kotanje sloni na avtomatizmu, ki izhaja iz večje stične površine prst/kamen kot jo ima začetna ravna površina (zdaj odprtina kotanje). Lijakaste vrtače se ob večanju kotanje običajno spremenijo v skledaste, kjer je preseganje večje. Na obliko vplivajo še prepustnost tal in soliflukcija. V zmernem podnebju je nudil dva milijona let dolgi pleistocen z večjo vlago iz snega in mehaničnim razkrajanjem kamna boljše pogoje za razvoj vrtač kot toplejša neogen in holocen, ko je človek bistveno skrčil primarno gozdno okolje in z njim procese v vrtači. Udornice niso upoštevane.

Geomorphogenetical processes of solution dolines are evident from restraints in their global and local distribution: more precipitation than potential evapotranspiration, permeable soil cover, water level and solution front (transition from aggressive to flowstone depositing water) below shallow epikarst, slope inclination below 30°, solid soluble rock. Dolines are an effect of local accelerated solution. In initial phase they are connected with more fractured stone, as the grains have greater specific (surface/volume) surface exposed to soil moisture. Effect of stone fracturing on solution was tested in laboratory. Later growth of basin is based on automatism, as the size of soil/stone interface is increased with deepening of the basin. Funnel-like dolines with growth usually convert in a bowl-like form with greater exceeding. The form is controlled also by water permeability of soil and solifluction. In temperate climate the two million year long Pleistocene offered with more moisture from snow and with intensive fracturing of stone better conditions for doline development than the warmer Neogene and Holocene when man’s impact in last centuries essentially redused primary forest environment and thus processes in the basins. Collapse dolines are not taken into account.