I think that it was a siege
Canadian shield is composed of Precambrian rocks that cover 2.8 million square miles.
Tundra is the climate zone that <span>has cool summers, cold and harsh winters, a dry climate, and sparse vegetation. Tundra is basically the type of biome where the growth of trees are hindered due to very short growth season and extreme cold. I hope that this is the answer that has actually come to your help.</span>