Geoscience Reference
In-Depth Information
Fig. 3.13
Fallen stalagmite
covered by new vertical
stalagmite in Elata Cave
springs is about 140 km
2
and covers a significant part
of Ponor Mountain. This was the reason for the search
for suitable seismodeformations in karst caves above
the springs.
During several visits in 2007, Elata Cave was
explored by Bulgarian and Hungarian scientists:
Dr. Katalin Gribovszki and Tibor Czifra from the
Geodetic and Geophysical Institute of the Hungarian
Academy of Sciences, Dr. Gergely Surányi from ELTE
University in Budapest, and Gabriel Nikolov and
Dr. Konstantin Kostov from the Geological Institute,
Bulgarian Academy of Sciences. The following indi-
cations of seismotectonic activity were identified:
(A) Fallen stalagmites. In the cave were estab-
lished 41 fallen stalagmites. Their size varies from 0.2
to 1.8 m (Figs.
3.13
. and
3.14
). Fallen stalagmites in
some cases are calcified to the floor and covered with
thick calcite crust, while others with regrowth of new
vertical stalagmites on the fallen samples. Their
substantial amount to their small dimensions of the
cave is a sign of the impact of seismotectonic events.
The rose-diagram of the spatial orientation of the
fallen stalagmites (Fig.
3.15
) clearly shows the pres-
ence of a preferred direction to the north. The formation
of well-defined maxima in the preferred direction of the
deformed speleothems is accepted as an evidence of the
seismotectonic origin of the perturbations (Dublyansky
1995
, 2000; Delaby
2000
). The Quaternary activation
of the sub-parallel fault structure expressed on the
surface near the cave is the probable cause of the seis-
motectonic phenomena as fallen and tilted stalagmites
and the breakdown. The cave is developed in the
hanging wall of the fault—an interesting relation that
was confirmed in paleoseismologic research in caves
from other karst regions of Bulgaria.
(B) Inclined stalagmites and stalagmite lines. The
strongly inclined stalagmite lines in Elata Cave are a
comparatively rare speleological phenomenon. The
inclined stalagmites have impressive size—height up
to 2 m (Fig.
3.16
). Their presence can be interpreted
as a result of slow subsidence of sediments below
their base, but the process of inclination itself is
probably helped by tectonic event.
(C) Inclined stalactones. In this cave were estab-
lished two inclined stalactones. The first column is at
an early stage of development of 55 cm height but the
other is massive, with a height of 1.6 m (Fig.
3.17
).
These formations are an extremely rare indication for
the presence of neotectonic activity and slow move-
ment along a fault (Jeannin
1990
);
(D) Open crack in flowstones. This fissure of
length about 14 m can be observed in the boundary
between undistorted, vertical stalagmites calcite crust
on horizontal and inclined array of stalagmites
(Fig.
3.18
). The depth of the crack is 2 m.
