geographia - Studia

ANDREA GÁL
of the material accumulated in the crater, this may be covered by a semisolid or partly solid
crust which usually quakes under one’s feet, especially if covered by vegetation.
One of the studied mud craters (Filiaş1) came into being through an eruption that
seems to have been triggered by an accumulation of gas (whose way to the surface was
blocked by mud) in 1913.
The samples collected from
the mud craters are poorly sorted
from grain-size point of view,
indicating a mixed origin of the
material. Due to the open mud
crater, the chance for an external
contamination is high, but at the
same time we can suppose an
internal contamination resulting from
the liquefaction of the surrounding
rocks.
3. 4. Mud pools
Mud pools usually appear as puddles filled with a very soft, liquid and in some
cases viscous material. Mud pools include all the negative and plain structures, even those
that have a small secondary and temporary cone (approximately 10 cm).
The mud accumulated in the pools may or may not be covered by vegetation.
When covered by vegetation, this quakes under one’s feet without visible gas bubbling. Gas
emissions are visible only after removing the vegetal cover, this having a dynamic evolution
and changing its density frequently, sometimes even disappearing for short periods.
The dimensions of a mud pool
vary from less than 1m until approximately
15m, and their depth ranges from 3 to over
8.5m. Any depth below this value remains
unexplored because of the lack of a drilling
set longer than 8.5 m. The drilling samplers
have “submerged” 8.5 meters in the liquid
mud which obviously was deeper than the
equipment. The mud pool is bordered by
the water-logged surrounding sediments.
Generally the fluid mud is bubbling
a %
100
90
80
70
60
50
40
30
20
10
0
100
and the emitted gas can be lit, nevertheless the quality and the origin of the gas are not
certain. Its color and the fact that it can be lit alludes to methane, but it is unknown if it
originates from the gas structures or it is just the result of the decomposition of organic
material (plants). Still, due to the semi-permanent flux of the gas we can assume that it is
related to the underlying gas structures.
In the studied area, as well as in the whole Transylvanian Depression, mud pools
are the most widespread features being known under several local names usually regarded
as “bottomless mud pits”.
Atid
Filia?1
10
Granulometric curves of the mud craters
Gravel Coarse sand Fine Sand Silt Clay
1
d mm
Fig. 9. Granulometric curves of the mud craters.
0.1
0.01
0.001
Fig. 10. Idealized sketch of a mud pool.
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