Just beyond the doorway he found the passage completely clogged and choked by impenetrable masses of shattered rock.

A high arctic desert, its interior is "an impenetrable mass of frozen crags and deep fjords."

In the forest, less thick, the trees were scattered in groups, and no longer formed impenetrable masses.

The trees no longer formed impenetrable masses, but their nature was more varied.

Their root balls rose fully twenty feet above the forest floor, their branches tangled into an impenetrable mass.

Space the plants so they will form an impenetrable mass at maturity.

Just outside Danane, the bush became a nearly impenetrable mass of mangrove and palm trunks.

City streets were an impenetrable mass of twisted metal, fallen bricks and wrecked office furniture.

The point's terminus was overgrown with what looked like an impenetrable mass of vegetation and palm trees.

The foliage was dense, an impenetrable mass that spread out almost horizontally near the bottom.