CART TRACKS
OF MALTA
OF MALTA
.
A lot has been said about the enigmatic
cart tracks of Malta Island and a lot had been speculated
on their depths, widths and origin. So far no one seems
to have been able to look at the problem of the track
dimensions and shape diversity from the point of view of
geomorphology of the development of karst surfaces on
limestone bedrock.
Lets start with the
chemistry of the limestone (this is also applicable to
dolomites).
Karst fields and cave
sinter are interrelated in their development by the
simple chemical process, where calcium carbonate of the
surface and subsurface limestone is dissolved by carbon
dioxide (CO2) contained in the penetrating water.
Rainwater picks CO2 up from the air as it develops in the
clouds and as it falls to the ground. The weak carbonated
water (carbonic acid) dissolves the limestone (calcium
carbonate) and penetrates the limestone porosity, cracks
etc. down into the interior of the limestone massive. It
eventually exits the limestone as seepage or an
underground creek. Wherever this weak carbonic acid
solution of calcium carbonate exits the limestone, it
looses its carbon dioxide content to the open air. The
carbon dioxide content in the underground water may also
be lost to other minerals contained within the limestone
where either oxidation or carbonation or both of other
minerals may take place.
As the carbon dioxide
exits the water, the originally dissolved calcium
carbonate crystallizes out of the solution and is left
behind as sinter, whose most generally known form are the
stalactites and stalagmites in caves.
There is also a
secondary process in the surface or subsurface rainwater
collected in the puddles and the soil moisture on the
surface of the limestone bedrock. As long as the bedrock
is covered by soil, which supports organic growth, the
surface water is enriched by carbon dioxide produced by
natural decay of plant and animal remains. In simple
terms, as the plant and animal life decays in the top
soil, the bacteria causing such decay release carbon
dioxide into the soil, which is consequently dissolved
into the surface water contained in the soil as well as
sitting on top of the soil in form of puddles and which
consequently etches the surface of the karst forming
bedrock (limestone and dolomites).
When the bedrock is
covered by a heavy cover of soil, the process of bedrock
surface deterioration eventually creates, given the time,
very deep and wide irregular indentations, which can
reach depths of tenths of meters, but which create more
less uniform mélange pattern of indentations on the
large scale of the field.
On the other hand,
where the soil cover of the karst forming bedrock is
relatively thin, the topsoil eventually collects in these
indentations as they deepen and as rainwater washes the
soil into them, but do not grow in width all that much.
But what has to be accounted for is also the topology of
the karst bedrock. Any sloping of the bedrock causes the
thin layer of top soil to be washed not only into the
karst indentation, but also washing of the topsoil into
the lower areas of the bedrock surface. This causes
collection of the topsoil in the lower elevations of the
bedrock leaving the higher areas exposed. Once the
limestone looses its topsoil cover all together, the
whole surface becomes subject to weathering while the
karsting process stops producing any more indentations of
an appreciable degree.
The problem with the
Malta cart track irregularities is fairly easily solved
once this karsting process is taken into consideration. I
am not going to enter into speculations of the initial
track origin and purposes, but it seems quite obvious
that the karsting process had its hand in the development
of these tracks as they can be seen today.
Once a cart has run
over the topsoil above the bedrock, especially when the
soil was moist, we can expect creation of soil ruts above
the bedrock. These ruts will first of all collect the
water from the surrounding soil as well as organic debris
and they will also retain the water longer, because their
soil had been compacted. This gives the water and the
organic decay produced carbon dioxide in the ruts an
appreciably longer period of time to work chemically on
the karst bedrock than the water in the soil next to it,
before the moisture soaks in and evaporates after a
rainfall. As the tracks are now being etched into the
bedrock surface, the topsoil starts collecting in these
stone tracks and the bedrock becomes exposed next to such
tracks. This more or less causes that the karsting
continues within the tracks only, where there is some
soil trapped in the track, leaving the rest of the
bedrock next to the tracks exposed to weathering.
The speed of karsting
depends on many local factors over the time of its
development. The few of them I know about are:
- Content of carbon dioxide in air
- General temperatures at the latitude and elevation.
- Annual rate of rainfall
- Rate of daily airborne condensation due to daily temperature variation
- Degree of vegetation and life as such in the locality
- Depth of the top soil
- Chemical and structural composition of the bedrock
When it comes to cart
track initiated karsting, there are also further factors
to be taken into the account. One of them is the
frequency of use of the “road”. A heavily used
track can be expected to be deeper than a lightly used
one. A deeper track in the overlaying topsoil can be
expected to collect organic debris and rainwater more
than a shallow one and therefore the karsting process
under and around the deeper soil track can be expected to
progress at a faster rate than under and around a shallow
track, due to the different rate of organic decay and a
period of retention of moisture.
When the topsoil from
the bedrock is washed away, except in its deep
indentations, it can be expected that the karsting
process will continue only inside such indentations,
while the rest of the karst field is exposed to
weathering. This means that if the initial cart track has
been indented into a shallow layer of top soil, where
only the bottom of the track is covered by soil, its
karsting can be expected to be narrow, even though deep.
When the topsoil layer was initially thicker, the
karsting can be expected to grow wide and deep.
This is somewhat
complicated by the accuracy of vehicles repeatedly
passing over a single track. I would be inclined to state
that the really narrow tracks represent single vehicle
pas over a quite shallow topsoil, while the wider tracks
represent single, or multiple passes over a relatively
thick topsoil layer. In my opinion, the haphazard tangle
of these tracks on Malta Island does not support a view
that they represent any particular roads.
The fact that the
Malta tracks often lead from nowhere to nowhere can be
possibly explained by patchiness of the topsoil cover at
the times of the track creation. A vehicle running over
exposed rock may have and probably did some abrasive
damage to the bedrock surface, but it would not initiate
the karsting process in the bedrock. Therefore, the
tracks should be generally found only in the shallow
depressions of the bedrock surface, while being virtually
non-existent on the bedrock humps.
Reading through Mr.
Graham Hancock “Underworld”, he has noticed a
jagged ridge of limestone between the “wheel
marks” of the same track. Such a ridge points to the
karsting process of development of the tracks quite
explicitly.
Since karsting is a
time dependent process, it can be to a degree used for
establishment of an approximate age of the tracks in
their relation to other objects on the locality. This
would have to be taken up with a geologist in conjunction
with archeologists.
If, for example, a megalithic building dated at
3000BC is standing on top of cart track 0.5m deep, and
the karsting process at that locality is estimated at
0.1mm/year, the track is obviously about 5000 years older
than the megalithic building and therefore dates at least
8000BC.
When quite different depths but consistent
widths tracks are found in the same general locality,
with generally the same type of bedrock, it points in the
direction of very long use of the locality by some kind
of vehicles taking eventually different routes.
When we find such
cart tracks under the sea, we have to understand that the
karsting process has stopped at the time these tracks
were flooded. If any of the submerged tracks should be at
least as deep as the tracks found on the dry land in the
same general locality, it is obvious that they are at
least as old as the period of time past since the
flooding, plus the duration of their development. In
other words, if lets say 500mm deep track sunk, or was
flooded 5000 years ago and the best guess on the karst
indentation development speed is again 0.1mm/year, these
tracks are some 10 000 years old.
The links below show
some of these tracks. The Czech site has actually very
good pictures of different tracks.
Disclaimer:
All numbers used
above are hypothetical and are not to be taken as
representative to the actual Malta situation. I am not an
expert. I am just a fellow, who done some cave exploring
in his time and who has learned and observed a few things
while doing so.
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