Development of A Plain
After 150 million years of volcanism, plutonism, metamorphism, and thrust faulting had run their course, the early part of the Cenozoic era (early Tertiary, 65–30 Ma) was a time of repose; neither igneous nor sedimentary rocks of this age are known here. A relatively featureless plain was created from erosion over many millions of years. Deposition resumed some 35 Ma in the Oligocene epoch on a flood plain that developed in the area; sluggish streams migrated laterally over the surface, laying down cobbles, sand, and mud. Outcrops of the resulting conglomerates, sandstone, and mudstone of the Titus Canyon Formation can be observed in road cuts at Daylight Pass on Daylight Pass Road, which becomes State Route 374 a short distance from the pass. Several other similar formations were also laid down.
Large volcanic eruptions, originating near the Nevada Test Site, covered the Death Valley area and much of Nevada in thick sequences of silica-rich ash 27 million years ago. The ash has a rhyolitic composition, which is the volcanic equivalent of the plutonic rock granite; it covered what would later become the Grapevine Mountains in 1,200 feet (370 m) of ash. This ash filled in valleys and depressions; by 20 million years ago, the region from the Death Valley area across Nevada was a volcanic plain.
Read more about this topic: Geology Of The Death Valley Area
Famous quotes containing the words development of, development and/or plain:
“Somehow we have been taught to believe that the experiences of girls and women are not important in the study and understanding of human behavior. If we know men, then we know all of humankind. These prevalent cultural attitudes totally deny the uniqueness of the female experience, limiting the development of girls and women and depriving a needy world of the gifts, talents, and resources our daughters have to offer.”
—Jeanne Elium (20th century)
“This was the Eastham famous of late years for its camp- meetings, held in a grove near by, to which thousands flock from all parts of the Bay. We conjectured that the reason for the perhaps unusual, if not unhealthful development of the religious sentiment here, was the fact that a large portion of the population are women whose husbands and sons are either abroad on the sea, or else drowned, and there is nobody but they and the ministers left behind.”
—Henry David Thoreau (1817–1862)
“To get time for civic work, for exercise, for neighborhood projects, reading or meditation, or just plain time to themselves, mothers need to hold out against the fairly recent but surprisingly entrenched myth that “good mothers” are constantly with their children. They will have to speak out at last about the demoralizing effect of spending day after day with small children, no matter how much they love them.”
—Wendy Coppedge Sanford. Ourselves and Our Children, by Boston Women’s Health Book Collective, introduction (1978)