Introduction :
During Carboniferous, our region was covered by a forest where there was a warm and humid climate and where inhabited large plants in shallow lagoons... Today, the landscape has changed but we can still find traces of these past times... Where? Under our feet, into this rock whith this unique color: coal.
Coal formation :
It was over 350 million years ago, at the end of the Paleozoic era during the period known as "Carboniferous". The Earth was then covered with many swamps and a lush vegetation and it was like a huge greenhouse where there was a hot and humid climate.
|
Everything starts in a swamp on the edge of a sedimentary basin (lagoon or lake); tectonic movements cause the rise of the sea, and the vegetation is then flooded. |
These plant debris accumulate and are covered with mud and sand layers (sedimentation). Buried debris are well protected from the air and do not rot. |
|
The vegetation reconstitutes... until the next engoulfing. |
|
Under the weight of sediments, the layers of dead plant sink and are subject to an increase of temperature and pressure which transforms them into coal, in fact, the cellulose, the major component of wood is first transformed into humic acids (products of its incomplete decomposition, which gives the soil a brown color), then into bitumen, and finally into elementary carbon.
This is a very long process: it is the oldest coals that have the highest carbon content (90-95%).
Reminder on "Earthcaches": There is no container or logbook on the given coordinates. Just visit the site and answer the questions by e-mail.There is no need to wait for my reply, feel free to log immediately after. If the answers are incorrect, I will let you know. Happy caching!
To validate your visit:
1-. During Carboniferous, where in the world globe was the Nord-Pas-De-Calais ?
2-. Which definition of subsidence is given in here?
3-. What is the name given to this long process?
4-. How many cycles were necessary for the formation of the 2,000 meters of coal lands of the Nord-Pas-de-Calais?
5-. How many kilometers long is the mining area of the Nord-Pas-de-Calais?
You can contact me in: English, French or Spanish.
|