Thread by @MiningNS

Paris’ #NotreDame Cathedral caught fire one year ago today. Read this thread to learn why the stone used to build it came from #Paris' catacombs.
#nspoli #cbpoli #novascotia #capebreton #geology

The limestone used to build Notre Dame formed 45 million years ago when Northern France was covered by a tropical sea. Limestone forms when bones/shells of sea creatures pile up and are compressed into rock.
#nspoli #cbpoli #novascotia #capebreton #geology #notredame

Limestone often has fossils in it as a result, like the clam in the picture below from #NotreDame.
Surface quarrying of limestone in the #Paris area started in the first century. Underground quarrying started in the 1300s and continued for centuries.
#nspoli #cbpoli #novascotia

As #Paris grew, quarry tunnels that had been outside the city were now inside it and some collapsed from the weight of buildings and traffic above. In 1774, 300 metres of a road called Denfert-Rochereau collapsed into a tunnel.
#nspoli #cbpoli #novascotia #capebreton #notredame

This problem continued and in 1776, Louis XVI signed a decree that prohibited extracting material from under public roads.
#Paris' growth also caused another problem around this time.
#nspoli #cbpoli #novascotia #capebreton #geology #notredame

Cemeteries in the city had been in use for centuries and they were overflowing with the remains of the dead - literally so during a 1780 flood. This led to the spread of disease and complaints about smells from cemeteries that didn’t have enough room to properly bury bodies.

In 1785 bones started being removed from the largest cemetery in #Paris, Les Innocents, which had been in use almost a thousand years. The bones were moved at night to minimize complaints from neighbours and were put in some of the abandoned quarry tunnels.
#nspoli #notredame

The emptying of cemeteries continued on and off until 1860. The bones of over six million people were eventually buried in the tunnels where the limestone used to build many of #Paris’ older buildings was quarried.
#nspoli #cbpoli #novascotia #capebreton #geology #notredame

In 1809, the catacombs were opened to the public for tours. Today #Paris’ catacombs get 550,000 visitors per year.
#nspoli #cbpoli #novascotia #capebreton #geology #notredame