The rocks that form the Canadian Shield were formed about two billion years ago, when they were under water in the Precambrian era. Most of Nova Scotia is rocky, with only a thin covering of soil, making it better for forests than farmland today. The area was under a shallow sea until 500 million years ago when primordial sandstone, quartzite, slate and granite oozed to the surface (you can see some at Peggy's Cove). Between 400 and 190 million years ago, the earth's heaving created contours and the hills and coastline. There are some fossils of trees in the cliffs at Chignecto Bay in the upper Bay of Fundy that date back 280-345 million years. .
Many of the rocks of these ancient layers were removed by the scouring action of glaciers that covered northern North America in the several ice ages in the past 100,000 years. The last ice age etched massive scratches into the rocks and left drumlins (piles of finely ground soil) behind, including the hill on which the Halifax Citadel stands. The province's best farmland is centered around such drumlin deposits.
The salt marshes and associated wetlands resulted from changes in sea level over the centuries. The tidal salt water marsh, fresh water marsh, uplands and bogs and the variations in between support a diversity of wildlife significant in the region. There are 57 rare vascular plants within the watershed, of which 25 are wetland species.
More history of Halifax