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.
Ponderosa Canyon is so named because of the huge Ponderosa Pines on the canyon floor. Some of these trees measure more than 5 ft. in diameter and exceed heights of 150 ft. However from high above at the viewpoint you would never know this. In fact many are confused by the name, not expecting to find themselves surrounded by a forest of Blue Spruce and Douglas-fir. Certain types of vegetation grow in certain environments according to conditions such as moisture and temperature. These conditions are strongly controlled by elevation. Forests, therefore, are divided into zones or forest types according to elevation, because a forest's dominant tree species varies with these changes in elevation.
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.
Agua Canyon Connecting Trail