G.K. Gilbert, a geologist who worked in the area in the 1870s, noted that the rock formations were "beautifully delineated on the slopes of the distant mountains, revealing at a glance relations that in a fertile country would appear only as the results of extended and laborious investigation." The rock layers that Gilbert noticed comprise a nearly complete record of the Earth's past, but that record has been jumbled out of sequence. The reason is that the rock layers that form the mountains are very ancient, but only in recent geologic time have they risen.
Even as the mountains rise, erosion began to wear them down. An example of this is the formation of the alluvial fans. Intermittent streams, resulting mostly from the bursts of infrequent rains, rush down the steep canyons scouring boulders, soil, and other debris and pushing and carrying the whole mass with it and then depositing it on the valley floor at the canyon's mouth.
On any given day, this valley floor shimmers silently in the heat. The air is clear—so much so that distances are telescoped—and the sky, except perhaps for a wisp of cloud, is a deep blue. Six months of the year unmerciful heat dominates this scene; for the next six the heat releases its grip only slightly. Rain rarely gets past the guardian mountains. The little that falls, however, is the life force of the wildflowers that transform this desert into a vast garden.
Despite the harshness and severity of the environment, more than 900 kinds of plants live within the park. Those on the valley floor have adapted to a desert life by a variety of means. Some have roots that go downward ten times the height of an average person. Some plants have a root system that lies just below the surface but extends out far in all directions. Others have skins that allow very little evaporation. Different forms of wildlife, too, have learned to deal with this heat.
The animals that live in the desert are mainly nocturnal, for once the sun sets, the temperature falls quickly because of the dry air. Night, the time of seeming vast emptiness, is actually the time of innumerable comings and goings by little animals. Larger animals, such as the desert bighorn, live in the cooler, higher elevations.
With height, moisture increases, too, until on the high peaks there are forests with juniper, mountain mahogany, pinyon, and other pines. And often the peaks surrounding the valley are covered in snow.
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