How Does Coal Form?

Nova Scotia has been mining coal commercially for 300 years, since the French established a mine at Port Morien in 1720 to supply coal for Fortress Louisbourg. But how did our world-class coal deposits form?

Nova Scotia’s coal deposits started forming 300 million years ago when NS had a tropical climate – tectonic plate movement had us in the middle of supercontinent Pangea, down around the equator.

Swamps contained dense vegetation that died, drifted to the bottom of the swamps and gradually formed peat—a soggy, sponge-like material. As the peat accumulated, the weight of the top layers compacted the lower layers by squeezing out water.

The peat was buried over time by sediments and ocean water. Deeper burial increased pressure and heat on the vegetation, causing chemical and physical changes, and pushing out oxygen. Over thousands of years, this turned the peat into the coal that still provides over half of Nova Scotia’s electricity.

Because of how it is compacted, it takes approximately 3-7 feet of plant material to form one foot of coal.

A coal seam one-metre thick can represent 2,500 to 5,000 years of plant accumulation in ancient swamps.

The thickest coal seam in Nova Scotia is the Foord seam in the Pictou Coalfield, which is 13.4 metres thick in places - representing 33,500 to 67,000 years of plant accumulation!

The picture below is the Foord seam at the Stellarton coal mine, which is fixing subsidence issues caused by 200 years of pick-and-shovel mining, including bootleg mines. The mine is reclaiming the site and making it safe to develop.