North Caves - Maastricht Underground

Transcription

SEE THE CITY FROM A DIFFERENT ANGLE
English brochure to use during a guided tour in the
North Caves
maastrichtunderground.nl
North CAVES
maastricht underground
Menu
Welcome
& safety
Art
formation of
limestone
The French
corner
The dome
Portrait of
D.C. van
Schaïk
Vault
The
Mosasaur
The block
breaker
Ground
plan
Bats
Flint stone
More
information
© Maastricht Underground / VVV Maastricht
North CAVES
MENU
Welcome to
the North CAVES
On behalf of Maastricht Underground
and Natuurmonumenten (Society for the
Presevation of Nature Monuments in the
Netherlands) we extend to you a warm
welcome to the North Caves.
You will visit the North Caves as part of a huge
network of around 22,000 underground tunnels
dug into this hill. The tunnel walls of this
enormous maze carry the signs of chopping
and cutting by block breakers as well as >
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North CAVES
MENU
many writings, drawings and sculptures.
Much of this was brought about for tourism
one hundred years ago. These signs of
chopping and cutting are the silent witnesses
of hard labour around the extraction of
marlstone in this area for 700 years.
In this document we describe the highlights
you may encounter during the guided tour.
Your guide will point out these highlights,
allowing you to look up all relevant information
in this document.
Some of the stops are not listed in this
document and some stops described in this
document are not part of the tour. The guide
will have to be selective in painting a varied
and full picture of events that happened at
this location through the centuries. On various
guided tours you will be visiting different
locations! Please feel free to ask questions.
We hope you will enjoy your guided tour!
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North CAVES
Safety
MENU
First of all we ask your attention for some
safety aspects:
• Gasoline lamps can be hot! Do you, or
someone near you, carry such a lamp? In
that case, please make sure that no one can
touch the top of the lamp.
•Some floors are uneven. Please take care
when walking on such floors.
• Please stay with your group and follow
the directions given by your guide. Do
not wander off through the tunnels in
the unlikely event that your guide is
incapacitated, but stay put until help has
arrived. Help is on its way for sure; no
further action is required.
• Please do not touch the walls or any objects
on the walls.
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Art
The temperature in these tunnels is always
around 11°C/52°F and the air humidity is around
98% (any time of the year, any time during
the day). The stone also retain a large amount
of water. That is the reason why most of the
drawings are sketched in charcoal; paint would
get mouldy and flaky. Charcoal will stay on the
wall as a powder coating for hundreds of years,
if it is left in peace.
Early in the 20th Century, local artists gave full
rein to their creativities in the hope that more
commissions might follow. >
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North CAVES
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Fuelled by mutual competition among the
four cave regions, the owners invited many
artists in an effort to make their ‘cave’ the
most appealing one for visitors. That resulted
in beautiful and authentic drawings and
advertising inscriptions, but also in imitation
stalactites and forgeries of old inscriptions.
One of the fine drawings is that of the more
than 100 years old Mary Stella Maris, depicting
the Onze Lieve Vrouweplein (“Square of Our
Lady”) with the basilica of the same name.
Facing the drawing of the Virgin Mary, you will
see a wall inscription from 1698 on your right.
The end of World War II marked the beginning
of mass tourism, and several educational
pictures were introduced in those days.
The most recent works were added to the
collection in the 1970’s.
The most remarkable ones are the very old
inscriptions. The oldest in these caves is from
1554.
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North CAVES
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The formation
of limestone
This drawing from 1954 gives an impression of
what the area must have looked like some 70
million years ago.
The mammoth (top right) did not arrive until
several million years later and neither should
the various dinosaurs (right) have a place
in this illustration. That is because in those
days (at the end of the cretaceous period)
the landmass of today’s Western Europe was
covered by a rather shallow, subtropical sea. >
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The nearest coastline was 50 km to the east.
Among the animals that lived in this region
(left) was also the mosasaur (centre). This
reptile was the largest glutton swimming
around. The animal would grow up to 17
metres long and ate everything that came on
its path, even its own sort.
After these local animal species died, they
sank to the bottom of the sea where the bodies
decomposed into calcareous remains. This
happened, layer upon layer, for millions of
years, resulting in the formation of limestone
layers with the help of the pressure of the
seawater above.
In fact, you are now walking in one giant
cemetery from the cretaceous period. Above
this tunnel is a 10m layer and under your feet
is another 60 - 70m layer of limestone.
Altogether that makes an 80m layer of animal
remains. >
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North CAVES
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Considering the cretaceous sea covered an
area from Ireland to Ukraine, you can imagine
the enormity of animal remains in this area.
No surprise that many fossils have also been
uncovered.
The layer in which these tunnels were dug
is mainly built up of the remains of algae,
foraminifers, single-cell organisms and other
very small animals. This caused the formation
of a homogeneous layer that became very
useful for making building blocks.
20 meters / 66 ft.
Soil
10 meters / 33 ft.
Limestone
10 meters / 33 ft.
Tunnels
60 meters / 197 ft.
Jeker
Meuse
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North CAVES
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The French corner
The French corner is the name given to part of
the caves housing the remains of improvised
facilities of three families of farmers built in
1794. They went underground in the caves to
flee the looming force of arms of the French
revolutionary troops. In this part we can
still see a bedroom, an oven fuelled by tree
branches, barns with troughs and halter holes,
and a 30m deep well. >
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In many places we can see reddish
discoloration on the marlstone walls. These
were caused by the heat from, most likely,
wood fires.
From the journal of B. Faujas de St. Fond, a
French naturalist who travelled with the army
to the conquered territories, we learned that
these farming families were found about three
weeks later. A pig that had torn itself free had
managed to reach the exit and was found by
the French soldiers. No mention was made
of the fate of those people after they were
discovered. >
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North CAVES
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Most of his book ‘Natuurlijke historie van den
St. Pietersberg bij Maastricht’ is about the
abundance of fossilised materials found at
this location. Since it was his field of study and
considering the time in which it was written,
we believe the facts as listed in the book are
accurate and correct.
However, we should take the stories in the
book about the adventures of the army and
the local population with a fair amount of
scepticism. After all, he wrote the book from a
French point of view.
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North CAVES
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The dome
During the siege by revolutionary troops under
the command of Klebèr in 1794, the French
made an attempt to blow up Fort St Pieter.
They had a rudimentary map of the
underground passages and planned to blow up
a pillar under the fort with gunpowder, after
which - or so they thought - the fort would
explode and come crashing down into the hill.
>
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North CAVES
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However, they failed to consider the fact that
pressure from the explosion would follow the
path of least resistance, which was not through
10 m of rock and 20 m of deposits but through
the sideways to the outside world instead.
So all they achieved was an enormous
collapse. For that reason, access to the dome
is only thanks to the numerous bracing walls
that were built at this location.
In the centre of the dome are some vague
remains of the pillar.
But even in the event that the explosion had
reached the aboveground area, the effects
would have been minimal as the fort is
about 150 metres away from this location.
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Portrait of
D.C. van SchaIk
This portrait was made in honour of engineer
Van Schaïk. At first, Mr Van Schaïk was com
missioned by marl processing company Nekami
in his capacity of electrical engineer to fix an
ever recurring short-circuit in the cableway.
The cableway was used for transporting the
excavated marl across the hill to the River
Meuse for further transport by boat. >
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North CAVES
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He suggested the construction of a tunnel
through the hill to eliminate any further
problems of the cableway.
He was commissioned for the realisation of
a tunnel that would be named after him. The
‘Van Schaïk Tunnel’ was completed in 1928.
During the preparatory work in the hill, he was
fascinated by its beauty, its history, and in fact
everything else surrounding the hill.
Using trigonometry, he mapped out all
accessible underground passageways together
with his son and an assistant in the 1930’s
and 1940’s. In addition, he was involved in
examining bats, research into inscriptions, as
well as the general history of St Pietersberg.
All this resulted in the 1938 publication of ‘The
St Pietersberg’, a reference work containing
all sorts of information about the hill, both
aboveground and underground.
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North CAVES
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Vault
The vault, or Rijksbewaarplaats (National
Depository) no. 9, is part of the caves that was
refurbished in 1942 with thick concrete walls,
a one-metre thick concrete ceiling and an air
conditioning unit.
About 800 works of art, until that year put in
storage bunkers along the coast of the North
Sea, were taken here for safekeeping. >
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North CAVES
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That was because the Nazi regime was
building its Atlantic Wall to resist an expected
invasion by allied forces from across the North
Sea.
Among these works of art was also
Rembrandt’s Night Watch, even in those days
insured for one billion Dutch guilders.
This enormous painting was removed from its
frame, rolled up and stored in a wooden crate.
Other works of art were placed in racks. These
racks are still present today. The paintings
were not sorted by the artist, style or time, but
they were spread among the available space
on the most economical way. Large paintings
were placed on wooden feet along the walls.
All around the vault is an impressive ‘rampart
walk’ in which the passages to the rest of
the caves were protected from any invaders
through walls, deep wells and concrete bars.
Armed (Dutch) military personnel were on
patrol here. >
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North CAVES
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The large tunnel (the Van Schaïk Tunnel) that
runs past the vault, was protected by Dutch
military police. The museum attendants were
ultimately responsible for the works of art.
They had their own waiting area in front of the
actual vault.
Contrary to common belief, these works of
art were not hidden but “simply” stored in the
vault. That was because the entire operation
was by order of the occupying forces with the
intention of taking all these works to Germany
after the end of the war. Fortunately, these
art treasure survived the war without any
damage and were later returned to where
they belonged, such as the Rijksmuseum,
Mauritshuis, Kröller-Müller, etc.
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North CAVES
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The Mosasaur
Sometime between 1770 and 1780, block
breakers were at work near this place. They
came across a piece of marl containing a 1.2
meter jaw, large teeth and the remains of a
skull. Army medical officer and fossil collector
Hoffmann was called and he bought the
discovery from the labourers. He concluded
that the remains had to be those of a crocodile
or a whale. >
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Remember that the worldview in those days
was entirely based on the Bible. According to
the Bible, the world was 6,000 years old and
God’s creations were perfect; for that reason
it was unthinkable that animals (life) could be
extinct. Any fossilised materials were therefore
classified under the existing system: crocodile
or whale.
More than 40 years after the discovery of what
was then called ‘the large fossilised animal
from the hill near Maastricht’, French
naturalist and zoologist George Cuvier had
another look at the remains. He concluded that
the animal remains were not that of a crocodile
or a whale, but rather resembled those of a
lizard-like creature, Saurus in Latin.
The remains were found near the River Meuse,
hence he called the animal ‘Mosasaurus’, or
‘Meuse lizard’. He also concluded that the
animal was no longer roaming the earth. In
other words, it was extinct. >
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North CAVES
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It was the first time that a statement like that
could be made under the revolutionary climate
in France in those years. And that is how the
discovery has contributed to the development
of the theory of evolution, which was further
worked out and published by Charles Darwin
(1859).
In 1794, the French took the original fossil as
a “war booty” back to Paris, where it remains
until this very day. All efforts to return ‘our’
Mosasaurus Hoffmannii to Maastricht have
failed miserably. However, various impressive
recent discoveries, the latest being that of the
6th of April 2015, soften the blow to some
degree. The relief looks very ingenious but it is
not a true-to-life rendering of the Mosasaur.
For more information and a large amount of
original fossils from the cretaceous period,
particularly of the Mosasaurs, we would
suggest a visit to the Maastricht Natural
History Museum.
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North CAVES
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The ‘block breaker’
The Romans excavated this limestone as early
as 2,000 years ago. They used it for marling
the land as well as for building blocks. They
worked from the side of the hill in an open-pit.
The tunnel construction started in the first half
of the 13th Century, when the city walls and
the large churches were built.
Building blocks were cut, on and off, in the
next 700 years. Much of it has disappeared
through cave-ins and industrial excavation. >
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North CAVES
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The block breakers who worked here in the
past were mostly peasants with a piece of land
on the hill. They also owned everything below
the surface of their land. In winter, the peasant
and one or two of his helpers came down for
excavation work on his own property.
But mining and agriculture are two very
different things, and they learned about the
rules of mining as they went along. This
quality of marl requires that the amount of
material removed may not exceed the amount
of material remaining as pillars to support the
ceiling. The “safe tunnel width” is four metres.
Overuse led to caving in.
Long working days with poor lighting from a
single oil lamp at a temperature of 52°F and
an air humidity of 98% takes a toll on people’s
health after a while. Today we know that the
lack of exposure to daylight may cause a range
of psychological and physical complaints. >
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North CAVES
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In addition, this particular climate may result
in a number of rheumatic and asthmatic
disorders. In short, difficult working conditions
and very poorly paid work.
During the first half of the 20th Century the
underground limestone excavation in St
Pietersberg came finally to an end. The usable
stone layers were all but run out. On top of
that, in 1926 the cement industry (ENCI) had
begun excavating the hill through opencast
mining using dynamite to blow up parts of it
and process the lime powder into Portland
cement in its large ovens. The ENCI concession
for the excavation of marl will expire in 2018.
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North CAVES
Ground plan
MENU
This ground plan is just an impression of the
large ground plan drawn by Ir. D.C. van Schaïk,
his son and an assistant in the 1930’s and
1940’s, showing all accessible passages in
those days. This map covers about a quarter
of the original map. The map shows two
passages at the red dot (‘you are here’). But
have a look around and you will see as many as
seven passages… >
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In short, not all passages are shown on the
map. The blue line on the right follows roughly
the path of this guided tour. The red line on
the left is the boundary line for the concession
of the industrial opencast mining pit of the
‘First Dutch Cement Industry’ (ENCI) for the
excavation for the cement production from
1926.
Everything on the left of the red line has
gone and, who knows, some of it may have
been used for the construction of your
home. At various locations on the plateau of
St Pietersberg you will be able to view this
enormous pit.
The ground plan also depicts the vault, the
dome with the collapse, the Fort St Pieter and
the entrance to the Zonneberg Caves.
The Zonneberg Caves are a little further south
and, just like the North Caves, they form part
of the large cave area there used to be. >
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The Zonneberg Caves provide an entirely
different experience. The Zonneberg has very
high, cathedral-like passages and has been
excavated in a very systematic fashion. The
Zonneberg has many relics from World War II
when the caves were used for evacuating
almost 50,000 habitants of the city of
Maastricht.
The Zonneberg story is certainly worth to be
heard.
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North CAVES
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Bats
St Pietersberg, since 1995 in the hands of the
Society for the Preservation of Nature, is also
known as a sanctuary for bats. In winter, after
the outside temperature has dropped below
zero and insect numbers have dwindled, the
bats seek shelter inside the caves.
Out of 19 bat species found in the Netherlands,
15 overwinter in these caves, 7 of which are
threatened with extinction. They sleep in even
the smallest nooks and crannies or hold on to
the walls. >
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Their body temperature drops to one degree
above the ambient temperature and their heart
beat slows down to two beats in 15 minutes.
These animals are not affected by light or
sound, but heat may upset them. Even the heat
from a torch may disturb their winter sleep.
Waking up drains them from two weeks of
sleep energy, so if this happens time after time
they may not make it until springtime.
The smallest species we may encounter in this
area is the common pipistrelle (Pipistrellus
pipistrellus). This bat would fit into a matchbox
and weighs as little as a sugar lump. The
largest species include the mouse-eared bat
and the pond bat, which are said to be as large
as a woman’s hand. >
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The bats are counted annually, and so we
know that almost one thousand bats spend the
winter months in these caves alone.
During springtime with the mercury rising,
these little creatures - by then as thin as a rake
- take to the skies and spend summer in trees,
church towers and under roofing tiles, some
of them as far as 300 km away. There they
indulge in insects and build up a layer of body
fat to survive the next winter months.
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North CAVES
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Flint stone
In all these caves we find a layer of dark stone
that runs like a horizontal plate across the
entire hill.
That is flint, officially named (black) silex, one
of the hardest types of stone on earth.
The marl workers ruined their tools instantly
after hitting this layer with their primitive saws
and chisels. Not surprisingly, this layer was
also dubbed the cursed layer.
They managed to get through the first flint
stone layer as they knew there was another
1½ - 2 m layer of good-quality marlstone
underneath. >
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The distance between the next layers got
smaller and smaller, and many more layers
followed still. This is the 23rd layer, counted
from the bottom up. Further mining produced
more broken tools than blocks of marl.
Contrary to popular belief, hitting two flint
stones together will not produce any flames or
sparks. In the Stone Age, when flint stone was
used to make arrowheads, axes and scrapers,
fire was made through friction heat.
It was not until the Iron Age that flint stone was
used to make sparks.
Making fire was by scraping the sharp edge of
the flint stone on a piece of iron.
Science is yet to come up with a generally
accepted explanation for the formation of flint
stone.
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North CAVES
More
information
MENU
We have come to the end of this guided tour
through the North Caves. We hope you enjoyed
your walk in this authentic part of the city of
Maastricht. We would like to hear your opinion
on this guided tour. To do so, please go to the
Tripadvisor website – Grotten Noord
For information on other locations of
Maastricht Underground, go to
www.maastrichtunderground.nl
or ask your guide.
For further information on Maastricht and how
you can make your stay extra special, surf to
www.visitmaastricht.nl
or see our colleagues at the Tourist
Information Office, Kleine Staat 1, Maastricht.
>
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North CAVES
MENU
More information about St Pietersberg and its
natural environment:
www.natuurmonumenten.nl
More information about geology,
the cretaceous period and fossils visit the
Maastricht Natural History Museum,
De Bosquetplein 7, Maastricht:
www.nhmmaastricht.nl
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