Although the trail was never particularly steep, the soft shale sloped gradually on the downhill side, perfect for twisting your ankles.

Even on weekdays, when visitors are few, almost two centuries of graffiti carved in the soft shale provides company.

When construction began, the mix of hard rock and soft shale under the mountains made digging difficult; at one point a boring machine was stuck for weeks.

The softer red shale below is eroded away by water, sand and gravel to form the plunge pool.

Some soft shale can be split with a pen-knife or even a thumb nail.

This fine group of belemnites is preserved on a soft shale.

This species is preserved in a soft shale, but one which allows for the skeletal anatomy to be preserved in its entirety.

The formation is composed of relatively soft grayish-red shale and olive-gray sandstone.

As the softer shale beneath the quartz eroded, the crust cracked, creating the misty, cold-trapping fissures.

The first such leaf, recovered in 1988 from soft shale in northern Idaho, was that of an ancient species related to modern magnolia.