How does Diana Wynne Jones use imagery in The Game?

Imagery:

"Her fingers were clamped round a pork chop. It was large. It was raw, and whitish with waterlogging, and sort of triangular, but there was no doubt what it was. It was almost exactly the right size and shape to block a drain."

"Hayley was just below it when the clouds suddenly smoked away from the rocky nose, for a moment unveiling piercing eyes and a stern mouth. Hayley nearly screamed. It looked exactly like Grandma's face made of stone."