Geology - Kejimkujik Seaside
© Parks Canada/P. Hope
With its kilometres of exposed coastline, the Seaside is a haven for those visitors interested in geology.
Band of mica in granite © Parks Canada/P. Hope
The rocks which make up Kejimkujik’s Seaside are very similar to those found in Kejimkujik inland. White granites and quartzites line the headlands and feed the cobble and rocky beaches. The granite is part of a major geological event that shaped western Nova Scotia. Known today as the North Mountain batholith, this enormous bubble of magma rose from the Earth’s interior. It ate its way into the existing rocks by following cracks and weaknesses and by heating and melting the rock. The intense heat generated by the magma caused the existing sandstones and slate to change, or metamorphose into quartzites and greywackes.
Linear veins © Parks Canada/J. Brownlie
Where the magma followed cracks and fractures, linear veins, dykes, and sills cut across older rocks. On the headlands veins and dykes of granite cutting through the darker metamorphic quartzites and greywackes are visible. The contact of this molten granite changed the metamorphic rocks in many interesting and observable ways.
The oldest rocks in the metamorphic greywackes and quartzites, are Cambrian in age, or 550 million years old. The granite is Carboniferous in age, or 352 million years old.
Erratic at Harbour Rocks trail © Parks Canada/P. Hope
The Ice Age also left its mark on Kejimkujik’s Seaside. The ice retreated from this area about 13, 000 years ago; almost 2,000 years before the inland portion of Kejimkujik. In some areas, the bedrock has been polished smooth when glaciers flowed over them. Thousands of large erratic boulders stick out through bogs and barrens, just where the melting glaciers dropped them. The soil of this land is often just a thin veneer of glacial till, composed of a mixture of sand, rock, and gravel that were left behind by the glaciers. It lacks many nutrients. The presence of thicker patches of soil determine where forests will grow as the trees prefer growing on deeper and more well-drained till.
During glaciation, sea levels were below present levels. Much of the world’s water had been removed from the ocean and captured in the form of ice. But, the Seaside contains visible evidence of a dramatic change in sea level. A walk along the shoreline at Harbour Rocks will reveal peaty muds, fossilized tree stumps on beaches, and soil layers on rocky outcrops or islands. These features only form inland where plant material can slowly accumulate. Soil does not form where crashing waves of salt water wash everything away. Trees do not grow on beaches. In fact, the fossilized tree stumps may be many thousand years old and were preserved deep underground. The post-glacial history of Kejimkujik Seaside can be viewed as a continual encroachment of the marine environment on the land. In recent memory, off-shore islands such as Little Hope Island were vegetated and supported small farms. Evidence suggests that the sea level continues to rise at a rate of 30 centimetres a century on the south shore of Nova Scotia. Add this to the ocean level increase due to global warming and it is clear that the Seaside’s coastline is going to continue to change.