O PROJEKTU | ABOUT THE PROJECT

Melišče (talus) je zbiralnik oz. nanos kamnitega drobirja ob vznožju skalne stene ali strmega pobočja. Je z vegetacijo neporaslo pobočje z nakloni 26° do 42°. Nastane s kopičenjem kamnitega drobirja, ki zaradi mehaničnega preperevanja kamnin in nestabilnega zemljišča pada s sten. Na melišča vplivajo vremenski pogoji, sestava kamnin, vpad skladov in voda. Kjer je proces kopičenja drobira počasen ali prekinjen nastane fosilno melišče, ki se laho zaraste z vegetacijo.

Melišča se nanašajo na sipek derobir in manjše skale na pobočju. Talus, soroden izraz, je pobočje z večjimi skalami in balvani.

Kjer je velika stenovitost, so ugodni pogoji za nastanek melišč, kjer pa je majhna, so pogoji slabi ali pa jih sploh ni. Nagnjenost pobočja mora biti takšna, da se na njem zadrži drobir oz. gruščnati material. Naklon melišča je odvisen od naklona podlage, na katero se odlaga gradivo.

Na kamnine delujeta tako fizikalno in kemično preperevanje in se medsebojno dopolnjujeta.

Mehanično razpadanje: material se odstranjuje s pobočij s hudourniškim odnašanjem izpod vznožja melišča in s samim vplivom deževnice in snežnice, ki odnašata s seboj droben material.
Veliko temperaturno nihanja povzroča temperaturno preperevanje, pri čemer je največkrat začetnik in pospeševalec prav zmrzal - zlasti na območjih z veliko padavinami in zmrevanjem vode v kamninskih razpokah.
Veter oz. eolsko delovanje tudi vpliva na nastajane melišč, vendarnima tako velikega vpliva kot temperaturno nihanje. Veter raznaša s sten v globino posamezne preperele delce. Prav tako povzroča premikanje delcev na samem melišču.
Na melišča vpiva tudi živi svet. Obiskovalci pospešujejo padanje kamenja s sten. S tekom po melišču premešajo gradivo ter tako vplivajo na njegovo sortiranost. Na ta način se ohranjajo v nižjih legah mnoga manjša melišča, ki bi se sicer fosilizirala. Divjad vpliva na melišče bolj ploskovno. Vpliv ni tako izrazit in opazen na prvi pogled.

Kemično preperevanje: na karbonatni grušč vpliva kemično raztapljanje (korozija) in odplavljanje karbonatov.

V osnovi ločimo dva tipa melišč: podstensko melišče, v katerih se zbira v stenah odkrušeno in odpadlo kamenje. Debelejše kamenje se kotali dalje, tako da je grušč na spodnjem robu debelejši. Značilen je enak naklon površja, ki je blizu nasipnega naklona, ki nastaja na stožcu nesprijetega kamenja, ki se nasipava z vrha. Naklon je med 29° in 33°, odvisno od debeline in robatosti kamenja. V Sloveniji so tovrstna melišča značilna za najvišja območja Kamniško-Savinjskih Alp, kjer so stene tako nizke, da v njih še niso nastali izraziti kamini. Pojavljajo se tudi pod stenami z največjimi relativnimi višinami, ko se vpliv kaminov zaradi velike površine, s katere pada kamenje, popolnoma izgubi.

Podžlebno melišče ima manjši naklon in je bolj raznoliko. V žlebovih in jarkih se zaradi plazov pozimi nabirata sneg in grušč iz ostenja, ki se prikotali po žlebovih. Če je na melišču sneg mehak, obtiči grušč na vrhu, po trdem snegu pa se razsuje daleč naokoli. Spomladi, ko se snežne padavine spremenijo v deževne, imajo v žlebu nastali hudourniki na vrhu melišča precejšno erozijsko moč. V sneg in gruščnato podlago vrezujejo korita.

Melišča pogosto prehajajo v hudourniške vršaje. Mejo pa lahko razmejimo glede na naklon, saj lahko pride gradivo v področje majhnega naklona le s pomočjo hudournikov in blatnih plazov, pa čeprav gre za direktno nadaljevanje melišča. So v nižjih legah, poglavitna razlika glede na melišče pa je v tem, da je gruščnato gradivo sekundarno transportirano. Ustvarja jih pretežno vodni transport. Nastajajo med obdobji hudih nalivov ali po intenzivnem taljenju snega pri čemer se tvorijo značilni nasipi.

Aktivna melišča so praviloma brez izrazite vegetacije, ko pa le-ta prevlada nad gruščem in gradivo veže med seboj, lahko govorimo o fosilnih meliščih.

Literatura in viri:

* 12. zborovanje slovenskih geografov, Kranj-Bled, 1981, str.147-154, Melišča v Kamniško-Savinjskih Alpah, Drago Kladnik;

* Proteus, št. 53 (1990-1991), str. 299-303, Dvojno življenje melišč, Ivan Gams;

* Brody, A. G.; Pluhar, C. J.; Stock, G. M.; Greenwood, W. J. (1 May 2015). "Near-Surface Geophysical Imaging of a Talus Deposit in Yosemite Valley, California". Environmental & Engineering Geoscience. 21 (2): 111–127.

A scree (talus) is a collector or deposit of crushed stone at the foot of a rock wall or steep slope. It is an unvegetated slope with slopes of 26° to 42°. It is formed by the accumulation of stone rubble, which falls from the walls due to the mechanical weathering of rocks and unstable land. The scree is affected by weather conditions, rock composition, stack intrusion and water. Where the process of debris accumulation is slow or interrupted, a fossil scree is formed, which is easily overgrown with vegetation.

The scree refers to loose scree and smaller rocks on the slope. A talus, a related term, is a slope with larger rocks and boulders.

Where there is a large wall, the conditions for the formation of scree are favorable, but where it is small, the conditions are poor or non-existent. The slope of the slope must be such that debris or lumpy material. The slope of scree depends on the slope of the base on which the material is deposited.

Rocks are affected by both physical and chemical weathering and complement each other.

Mechanical disintegration: the material is removed from the slopes by torrential drift from under the scree and by the influence of rainwater and snow, which carry fine material with them.
A large temperature fluctuation causes temperature weathering, and most of the time frost is the initiator and accelerator - especially in areas with a lot of precipitation and water freezing in rock cracks.
The wind or aeolian action also affects the resulting scree, but with as great an influence as temperature fluctuations. The wind blows individual weathered particles from the walls into the depths. It also causes movement of particles in the scree itself.
The scree is also inhabited by the living world. Visitors accelerate the falling of stones from the walls. By running on scree, they mix the material and thus influence its sorting. In this way, many smaller screes are preserved in the lower areas, which would otherwise be fossilized. Game affects the scree more flatly. The effect is not so pronounced and noticeable at first glance.

Chemical weathering: carbonate aggregates are affected by chemical dissolution (corrosion) and leaching of carbonates.

Basically, there are two types of scree: sub-wall scree, in which crushed and fallen stones are collected in the walls. Thicker stones roll further, so the gravel is thicker at the bottom edge. It is characterized by the same slope of the surface, which is close to the embankment slope, which is formed on the cone of loose stones, which is filled from the top. The slope is between 29° and 33°, depending on the thickness and ruggedness of the stones. In Slovenia, this type of scree is typical for the highest areas of the Kamnik-Savinja Alps, where the walls are so low that distinct fireplaces have not yet formed in them. They also appear under walls with the greatest relative heights, when the influence of fireplaces is completely lost due to the large area from which the stones fall.

The sub-channel scree has a lower slope and is more varied. In the gutters and ditches, due to avalanches in the winter, snow and gravel accumulates from the debris that rolls down the gutters. If the snow is soft on scree, the gravel gets stuck on top, but on hard snow it is scattered far and wide. In the spring, when the snowfall turns into rain, the torrents formed in the gully on top of the scree have considerable erosion power. Troughs are cut into the snow and gravel base.

The screes often pass into torrential screes. The border can be demarcated depending on the slope, since material can only reach the area with a small slope with the help of torrents and mudslides, even if it is a direct continuation of scree. They are in lower positions, and the main difference compared to scree lies in the fact that the aggregate material is transported secondarily. They are mainly created by water transport. They are formed during periods of heavy downpours or after intense melting of snow, forming characteristic embankments.

As a rule, active scree is devoid of distinct vegetation, but when it dominates the gravel and binds the material together, we can speak of fossil scree.

Literature and sources:

* 12th meeting of Slovenian geographers, Kranj-Bled, 1981, pp. 147-154, Melišča in the Kamnik-Savinjske Alps, Drago Kladnik;

* Proteus, no. 53 (1990-1991), p. 299-303, The double life of scree, Ivan Gams;

* Brody, A.G.; Pluhar, C.J.; Stock, G.M.; Greenwood, W.J. (1 May 2015). "Near-Surface Geophysical Imaging of a Talus Deposit in Yosemite Valley, California". Environmental & Engineering Geoscience. 21 (2): 111–127.