How does Edward Rutherfurd use imagery in Sarum: The Novel of England?

Imagery:

"The land that Hwll's ancestors had crossed was all gone, and for the whole of his short life, he had no longer been living on a peninsula of Eurasia, but on a new island. Because of that arctic flood Britain was born, and for the rest of her history, her people would be separate, protected from the outside world by a savage sea."

"And now, at the place where the five rivers met, there was a new presence in the valley: in the gentle curve of the river a mile below the castle hill, a large area had been cleared and there, where before had been only broad meadows dotted with trees, a huge building site, several hundred acres in extent, was slowly rising."