Geoscience Reference
In-Depth Information
three strong seismic events took place here—the
Gorna Oryahovitsa earthquakes of June 14, 1913
(Ms = 7.0, Focal depth = 7 km) and December 19,
1914 (Ms = 4.7), and the Strazhitsa earthquake of
1986 (Ms = 5.7). According to historical data, nine
earthquakes with magnitude up to 7.2 are known in
the period 536-1890. The epicenters of these events
are Veliko Tarnovo, Gabrovo, Lyaskovets, and the
village of Arbanasi (Grigorova and Grigorov
1964
,
Orizova-Stanishkova et al.
1996
).
The Troana Cave is mainly made up of a large
downdipping gallery with a stream flowing along its
length and a maze system of fossil passages which
together form a total length of 2,750 m (Fig.
3.37
).
This ponor cave is entered from a doline which col-
lects the surface streams (only during peak runoff) of
two dry valleys. The entrance parts are narrow with
few steps up to 3 m deep. After the entrance squeezes,
the original morphology of the cave is blurred by
collapse phenomena—the floor is covered by impres-
sive breakdowns, partially coated by speleothems.
The mezokarstic deposits are presented by fluvial,
detritic ones and plenty of various attractive speleo-
thems: stalactites, stalagmites, columns, flowstones,
draperies, etc. According to its rich sinter decorations,
Fig. 3.33
Displaced stalactone in Saeva Dupka Cave
Fig. 3.34
Fractured massive
stalactone in Saeva Dupka
Cave
