THE GRADUSA CAVE
Although
the existence of the Gradusa Cave had been known of for a long time to the local
population, only recent speleological explorations, by the members of the
speleological department within the Mounainteering Society of the «Velebit»
University from Zagreb, have discovered the riches of the underground and
various speleological phenomena in its interior. Located in the village of
Velika Graduša, with its entrance in an abandoned stone-pit, the cave presents
a previously unknown natural resource of this region.
The Gradusa Cave was produced by the formation of underground cavities
during the process of the karstification of rocks in the area. The rocks in
which the cave had “grown” were formed by leaving behind sediments in the
sea which long ago covered the region. As the sea withdrew and the rocks came to
the surface, the conditions were created for development of underground
chambers. In the newly formed cavities, in the darkness of underground, a new
life began – water dripped in and grew stone ornaments… This story began
some 10 million years ago and continues until today.
The
entrance of the cave was opened during the works in the stone-pit. Although it
is not known exactly when the exploitation of the stone in Graduša started, it
dates back to the Turkish rule. Since then, the entrance area, the more easily
accessible part of the cave, has probably been visted from time to time.
Nevertheless, the recent speleological explorations of the cave do not show
evidence of people ever walking through the further sections of its tunnels.
Difficult
narrow passages, partially flooded tunnels and slippery walls of mud, ensure it
is classified in a very demanding speleological category. Albeit, the efforts
made to overcome the difficulties to gain entry to the first part of the cave,
abundantly reward with a view of the ample ornaments in this cave and in the
depths of its tunnels. This particular morphology has made the process of
exploration difficult at the beginning, so that the total length of the cave of
455 meters was reached only after repeated attempts during the course of a year.
The
cave’s main tunnel clearly runs along a direction of northwest to southeast.
Just before half of its lenght, two forks separate; one is a dead end meander,
only 12,5 meters long, whereas the other fork meanders into the water filled
floor. Due to narrowness of this meander, and the need for diving suits in order
to make further progress, this fork has not been further explored. The flooded
sections of the main tunnel interchange with the dry sections. However, its way
out is completely flooded. The further, dry part of this tunnel is richly filled
with cave ornaments – stalactites, stalagmites, stone draperies and columns,
even helactites. In its rear section, there was an attempt to dig a passage at
the spot suspected to hide a continuation of the tunnel, but a rock-slide put an
end to it. Beside the main tunnel, another side passage branches off from the
entrance chamber and runs down to the water filled floor. The rest of the tunnel
is completely flooded, which makes futher progress impossible.
Today this cave provides shelter to a large colony of bats which can be
seen at sunset flying out of the narrow entrance of the cave. That may not be
the only entrance to the Graduša Cave, but it is the only one known so far.
Regarding other entrances to the Cave, it would definitely be worthwile
consulting local bats…
Althogether 19 speleologists, members of the speleological department of
the Mountaineering Society of the «Velebit» University from Zagreb, have
participated in the explorations of the cave and their research has been
documented by digital photo material and by drafting a detailed ground-plan of
the cave.
Darko Štefanac
Planinarsko društvo Sveučilišta
«Velebit»