Just as geology determines biology, biology also impacts the geology. From this vantage point you can see how the type of rock that composes the different steps of the Grand Staircase determines what kinds of plants can grow on it. The varying densities of vegetation determine how erosion shapes the land.
In the slick rock sandstone of the White Cliffs the soil is thin or nonexistent and plants cannot easily take hold. The lack of plants causes this region to endure intense erosion with each rainstorm forming deep canyons, rounded domes and pointed nipples.
Where the roots of trees and plants can get established they help stabilize the soil and rock underneath. This is evident in the Grey Cliffs, the sequence of rock that lies above the White Cliffs. The Grey Cliffs are made of rock that consists of a combination of sand, shale, and clay. This combination produces better soils allowing dense vegetation, which better protects the rock underneath by absorbing some of the rainfall and preventing flash floods.
Notice how canyons through the Grey Cliffs are wider, meander more, and aren't as deep as those through the White Cliffs? The difference is the presence or absence of flash flood erosion. Even though the White Cliffs are composed of more durable rock than the Grey Cliffs, they still erode at a faster rate! Just as geology influences plants, plants control geology.
Bryce Canyon National Park encompasses three of these forest types from the lowest elevations below the rim of the canyon to the upper elevations in the southernmost end of the park. At the bottom is the Pinyon-Juniper Woodland Belt, dominated by the Pinyon Pine and the Utah Juniper. The rim of the canyon in the northern end of the park is dominated by the Ponderosa Pine, and is thus classified as a Ponderosa Pine Forest. At the highest elevations, like here at Ponderosa Point, Blue Spruce, Douglas-fir and White Fir are the most common tree species, indicative of a Spruce-Fir Forest.
Last updated: March 31, 2012