 |
|
A few words about geology...
|
The cave that has been opened
up forms part of an underground system that was formed at the beginning
of the Tertiary era, in other words, about 60 million years ago. Between
that era and our own, the cavity evolved through a series of changes,
which is even now quite difficult to piece together. What one can
say is that the flow of water that carved out the galleries and deposited
alluvia slowed down with the deepening of the river-valleys. Following
climatic changes, the cave was subjected to complex phases of in-fill
by sand and clay, washed in from the exterior, alternating with phases
of further carving-out. The concretion visible today dates from the
latter period, spanning thousands of years, and can only have been
formed in those voids that were not affected by sand and clay in-fill.
What
makes for the importance of this cave is the quality of its concretion.
This is the term used for mineral deposits that form on the walls
of a cave by crystallisation of calcite (calcium carbonate) carried
in solution by infiltrating water. When this water drips from the
roof of a cavern, it deposits a small amount of the calcite that was
dissolved in it. Over the centuries, this produces a more or less
cylindrical cluster of calcite crystals that forms downwards, which
is called a stalactite. Similarly, a deposit is formed on the floor
of a cavern when a droplet of water falls, forming little by little
what is called a stalagmite. One can understand that, following the
intensity of the infiltration of water, the shape of the galleries
and other conditions, these concretions can take on extremely varied
forms, in the shape of columns, draped fabric, etc.
The shapes of concretion formed
by calcite which are both the most rare and the most curious are those
referred to as eccentric. This type of concretion forms finger-like
patterns, twisting in all directions, seeming to defy the law of gravity.
It is made possible by a combination of several factors: the particular
porosity of the rock, and a constant but very slight flow of water
through the roof of the cave. In this way (and to simplify a little)
the water, laden with calcium salts, evaporates against the cavern
wall without falling to the ground (furthermore, that leads to the
formation of very few stalagmites in the cavern). The water weeps
slowly, penetrating all the porous sections of the cavern wall and
of the concretions that have already formed. The water is subject
to the force of capillarity, on this scale greater than the force
of gravity, and can climb just as well as it can descend. In this
way it deposits particles of carbonate in every possible direction,
seeming to defy, as one often says, the law of gravity.
|
|
Eccentric
concretions...
...beautiful
formations of crystal
Masterpiece
of Nature
|
This
effect is particularly astonishing and can only be observed in a fairly
small number of caves where the criteria of the porosity of the limestone,
the flow of water filtering onto the walls and the micro-climatic
conditions of the cavern all coincide to allow their formation.
It is precisely this type of
eccentric concretion that one may observe in the
Maxange Caves. They form bouquets that decorate the roof
and walls over a considerable distance. Their profusion, delicate
form and purity, sparkling under rays of light make a display of rare
quality, which fully justifies the project of development.
The Maxange Caves are one of
the finest examples of what is referred to in geological terms as
a "geode". |
|
|
 |
|
|
|
 |
|
|
|
 |
|
|
|
