Seal Island Bridge

It’s a campground today but it used to be a quarry, another example of how former mines and quarries often become parks and recreational areas after extraction is completed.

The KOA Campground next to Victoria County’s Seal Island Bridge used to be a quarry.

The bridge, officially called the Great Bras d’Or Crossing, opened in 1961 and is an important link in the Trans Canada Highway between Sydney and Baddeck. It is the third longest bridge span in Nova Scotia.

An extensive search did not turn up any documentation about the quarry’s history. However, local knowledge suggests it provided aggregate for the construction of roadways leading to Seal Island Bridge. It is also said that a number of companies have used stone over the years that fell naturally from the quarry’s face as a result of winter’s freeze/thaw cycle.

Anyone who has driven on the bridge likely noticed the striking pink granite cliffs on the New Harris side, which used to be the quarry face. The pink colour comes from iron in the rock.

The granite formed about 498 million years ago during what geologists call the Late Cambrian period. The Earth was a very different place back then. Prior to the Cambrian Period, which ran from about 541 to 485.4 million years ago, most life on earth was microscopically-small bacteria. The continents were still forming and land was mostly barren, without plant or animal life.

The “Cambrian Explosion” saw the development of a wide range of more complex life forms, mostly in water. Trilobites developed, one of the first animals to have eyesight, as did mollusks, worms and sponges. Animals like arthropods and brachiopods developed shells, external skeletons and spikes for defense, the first time this happened.

Most plant life during the Cambrian was single-celled algae, many of which grew together to form large colonies that resembled large plants.

Sea levels and global temperatures generally rose during the Cambrian. This likely contributed to the development of new animal life as seas flooded low-lying lands, creating shallow marine habitats that were ideal for spawning of new life forms.

Oxygen levels also rose during the Cambrian as cyanobacteria and algae used sunlight, water, and carbon dioxide to create oxygen and energy (photosynthesis). The higher oxygen levels also likely supported the development of more complex life.

The Cambrian also had several mass extinction events in which much of the life on Earth was killed but then recovered and evolved.

It is amazing to think that the granite we see at the campground today was around when such profound changes were taking place.

Our knowledge of the Cambrian period, as with so much of Earth’s distant past, comes from fossils and other evidence in what we call the Rock Record – our planet’s history as recorded in our geology.

Seal Island Bridge under construction.