The Scarborough Bluffs' Erosion

The Scarborough Bluffs run for roughly 15 kilometres along Toronto's eastern Lake Ontario shoreline, rising in places to about 90 metres above the water. They are not bedrock: the bluffs are a stack of unconsolidated sand, silt and clay laid down over roughly the last hundred thousand years, recording a sequence of interglacial lake beds and glacial deposits that geologists use as a reference section for the region's ice-age history. That same softness makes them spectacular to look at and constantly unstable, as wave action, groundwater seepage and freeze-thaw cycles undercut the slopes.

A managed shoreline

Elizabeth Simcoe, wife of Upper Canada's first lieutenant governor, is credited with naming the bluffs in 1793 for their resemblance to the chalk cliffs at Scarborough, England. Serious, coordinated efforts to control the erosion date largely to the years after Hurricane Hazel struck the region in 1954, which pushed the province to expand the powers of conservation authorities, including the Toronto and Region Conservation Authority. Along the bluffs, that has meant decades of shoreline armouring with interlocking blocks at the base of the slopes, combined with the construction of Bluffer's Park in the 1970s and 80s, which used lake-filled land to push the shoreline outward.

Sources

• Wikipedia — Scarborough Bluffs
• Toronto and Region Conservation Authority — Scarborough Bluffs