De tre cacher Tvis Mergelgrav (rød rute) og Dyr og kryb (rød rute) og Planter og træer (rød rute) er tænkt som en lille 'forlængelse' af vores Adventure Lab "Tvis Mølle Naturlaboratorium". De kan dog snildt findes uafhængigt af hinanden.
[DK] OBS ! nogle steder kan være stejle og glatte. Færdsel i området sker på eget ansvar.
For at komme i nærheden af cachen skal du gå med RØD RUTE og anbefales først forlade stien når du er lige ved cachen.
Der kan være græssende får på noget af ruten.
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[GB] NOTE ! Be careful - some places can be steep and slippery. When you are in the area it's your own risk.
To get close to the cache, go along the RED ROUTE and recommend to only leave the path when you're right at the cache.
There may be grazing sheeps on some of the route.
Tvis Mergelgrav
I dette smukke landskab ses historiske spor fra mergelgravning. Indtil 1960 gravede man mergel op her ved Tvis Å. Det var hårdt arbejde. I tørvejr er ler hårdt at grave i, og i vådt vejr er leret glat og mudret og sværere at stå fast i. Man kan let forestille sig, at det var et meget slidsomt arbejde at grave mergel op. Da udgravningen var på sit højeste her på stedet, var 60 - 70 mand beskæftiget.
Hvad er mergel
Mergel er kalkholdigt ler med mindst 10% kalk. Denne jordtype har vi haft meget af i Danmark. Det stammer helt tilbage fra istiden, hvor isen har flyttet godt rundt på lagene i undergrunden, og hvor moræneler derved er blevet blandet med det underliggende kridtlag (kilde: Wikipedia).
Mergel til jordforbedring
Kalken giver gode vækstbetingelser til afgrøder og det har man brug for i landbruget til forarbejdning af jorden, og især jord som endnu ikke er dyrket. Førhen var der meget uopdyrket jord i det midtjyske. Der er meget hedejord i det midtjyske og dette er mere surt. Sur jord har en lavere pH-værdi og det gavner ikke væksten af landbrugsafgrøderne. Derfor tilføjede man mergel til jorden. Jo mere kalk i leret, jo bedre var det til jordforbedring i landbruget. Her ved Tvis havde man et stort behov for kalk til alt det uopdyrkede jord, som man tog hul på at dyrke i starten af det 20. århundrede.
Enkelte gårde kunne forsyne dem selv med mergel, men de fleste havde brug for denne fælles mergelgravning her fra Tvis Mergelgrave. Virksomheden var en af de store og den var industrialiseret organiseret med opgravning, transport og salg. Man lagde skinner ud fra omådet, så damplokomotiver kunne fragte merglen ud til landmændede. Senere transporterede man med lastbiler.
Ekstra info
For særlig interesserede er der faktisk en masse at læse om stedet her
hvis du googler ordene: Tvis mergelgravning
[GB] google translated
NOTE !!!! Be careful. When you are in the area it's your own risk. Some places can be steep and slippery
To get close to the cache, go along the RED ROUTE and recommend only to leave the path when you're close to the cache.
There may be grazing sheeps in the area.
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In this beautiful landscape, historical traces of marl excavation can be seen. Until 1960, marl was dug up here by Tvis Å. It was hard work. In dry weather, clay is hard to dig in, and in wet weather, the clay is slippery and muddy and harder to stick to. One can easily imagine that it was a very tiring job to dig up marl. When the excavation was at its height here on the site, 60-70 men were employed.
What is marl
Marl is calcareous clay with at least 10% lime. We have had a lot of this type of soil in Denmark. It dates back to the ice age, where the ice has moved well around the layers in the subsoil, and where moraine clays have thereby been mixed with the underlying chalk layer (source: Wikipedia).
Marl for soil improvement
The lime provides good growing conditions for crops and this is needed in agriculture for the processing of the soil, and especially soil that has not yet been cultivated. Previously, there was a lot of uncultivated land in central Jutland. There is a lot of heathland in central Jutland and this is more acidic. Acidic soil has a lower pH value and it does not benefit the growth of agricultural crops. Therefore, marl was added to the soil. The more lime in the clay, the better it was for soil improvement in agriculture. Here at Tvis, there was a great need for lime for all the uncultivated land, which was started to be cultivated at the beginning of the 20th century.
A few farms could supply themselves with marl, but most needed this common marl digging here from Tvis Mergelgrave. The company was one of the big ones and it was industrialized organized with excavation, transportation and sales. Rails were laid out from the area so that steam locomotives could transport the marl out to farmers. Later they were transported by truck.
Extra info
For those particularly interested, there is actually a lot to read about the place here
if you google the two danish words: TVIS MERGELGRAVNING