Five thousand years ago a huge glacier, a mile thick covered what is now Vancouver, BC.
As this massive ice sheet flowed down the Fraser Valley and across the Lower Mainland, it pushed and crushed mountains of rock in its path. When the giant ice sheet receded back up into the mountains at the end of the last Ice Age it deposited millions of large boulders in its wake.
These glacial erratics remain scattered all over Vancouver, usually buried below the city. As Vancouver grows and the land is developed and redeveloped these ancient boulders are exposed by excavation and removed, once again setting them in motion.