Most of Salt Spring Island consists of folded sedimentary rocks of the Cretaceous Nanaimo group. They range from conglomerates to finely bedded turbidites.
The structure of the folded rocks appears at various scales - from the overall shape of the Gulf Islands to small-scale deformation within individual outcrops. Locally, they conspired with the glaciers to form narrow inlets, often with small pocket beaches tucked into their ends.
AERIAL VIEW (Google Maps)
The beach in Vesuvius Bay is a nice example of a small pocket beach perched on top of steeply-dipping Nanaimo silts and sands. The slowly eroding bedrock probably doesn't generate much sediment, so the beach probably accretes very slowly, if at all.
There are many other pocket beaches on Salt Spring - some I've visited before (Beddis Beach 2008, Southey Point 2010), some I'll visit in the next few posts.