Two isolated hills of unusual interest rise above the plateau surface near Grand Canyon. Looking east from Desert View (Navajo) Point one of these, a flat-topped mesa called Cedar Mountain, may be seen. The other, known as Red Butte, is a rounded hill about fifteen miles to the south of Grand Canyon village. The most interesting feature of these hills is found in the fact that they are composed for the most part of red sandstones and shales which once formed a continuous layer over this entire plateau region. These same rocks are found throughout southern Utah to the north, and in the Painted Desert to the east. Except at Red Butte and Cedar Mountain they have been completely stripped off and eroded away from the vicinity of Grand Canyon. The time involved in this erosion was tremendous and the consequences widespread. As a result the present flat plateau surface was formed—a great plain high above sea level. The persistence of Red Butte and Cedar Mountain against time and the elements is easily explained, moreover, by the hard lava cap of the former and the protecting layer of pebble-rock on top of the latter.
CEDAR MOUNTAIN
RED BUTTE
The red sandstones and shales found in Red Butte and Cedar Mountain were formed from sands and muds accumulated during the early part of the Triassic Age—the beginning of the fourth great era of history. Near Flagstaff at the southernmost limit of the formation have been found many tracks and trails left by small crawling animals which indicate a shore environment in that section. In the same formation found in Utah and other places to the north are many seashells of various types. Gypsum, an indication of arid climate, is also found to a large extent in the rocks of this group.
THE PETRIFIED FOREST
(SHINARUMP AND CHINLE FORMATIONS; TRIASSIC PERIOD)
The Petrified Forests of northern Arizona and southern Utah were formed from trees which grew during a period known as the Triassic. The type of environment in the Painted Desert region during that period makes a very interesting speculation. The landscape of this ancient country, as interpreted from the present rock formations found there, was that of a low, flat area, perhaps a floodplain, where rivers and streams meandered back and forth, depositing first large pebbles and sand, and later a great thickness of finer material consisting of sand and much mud. It was by these streams that a great quantity of logs of evergreen trees was carried down probably from mountains to the south or southwest. Many of the tree trunks were worn and battered on the way, and in this region (from southern Utah to the vicinity of Adamana and Holbrook) they were buried in great numbers among the depositing sediments. All four of the Petrified Forests south of Adamana originated in this manner—and probably represent old log-jams. Nine miles north of Adamana, however, is the North Sigillaria Forest where the trees are found standing as they grew.
PETRIFIED FOREST. ARIZONA