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Ancient Landscapes

The badlands below you are formed from a colorful
sequence of rocks called the Chinle Formation.
Most of the rocks are soft, fine-grained mudstone,
siltstone, and claystone.

Have you noticed the step-like features on the
hillsides below? These are the result of mass
downslope flowage. During summer downpours,
clay in the outer layers absorbs water and becomes
heavy and pliable. Eventually, gravity causes the
water-saturated clay to creep down the steep
slopes, forming these steps.

The most recognizable sediment in
the Painted Desert is the Black
Forest Bed, a whitish layer
composed of water-deposited
volcanic ash and silt. This white
siltstone is cemented better, and
therefore more resistant to erosion
than the pink clays. As a result,
erosion and weathering remove the
softer pink clays more rapidly,
leaving the Black Forest Bed as
a resilient ledge.

The surface along the trail is
volcanic agglomerate, made up of
ash, cinder, and lava. Agglomerate
provides a richer, more stable
surface for growing plants. These
volcanic rocks were ejected from a
nearby volcanic vent about 6 to 8
million years ago.

Don't miss the rest of our virtual tour of Petrified Forest National Park in 1519 images.