Island in the Sky
As the map ([fig. 1]) shows, Island in the Sky is really a fork of a wedge-shaped peninsula extending southward between the two rivers. An outlier to the south named Junction Butte has already been severed from the main peninsula by erosion and now is a true island. (See [frontispiece] and [fig. 22].) A large chunk of Island in the Sky south of The Neck was about to be severed by erosion from the main peninsula to become a true island, when recent widening and grading of the road gave it a temporary reprieve. When my family and I first squeaked over this narrow neck in 1960 by jeep, furtive glances to right or left showed the two canyons perilously close, and complete severance seemed imminent. The road builders have staved off disaster for a few thousand years, but ultimately the large section to the south will become another island, and a bridge will be required to connect it to the mainland. Its appearance from the air before the road widening is shown in [figure 11].
AERIAL VIEW OF THE NECK AND SHAFER TRAIL, looking southwest, taken before rebuilding of park road on mesa top. Cliff-walled canyon to right of The Neck, in middle, drains westward to the Green River; south fork of Shafer Canyon to left drains eastward to Colorado River. This is the narrowest part of Island in the Sky. Photograph by National Park Service. (Fig. 11)
The entrance road to Island in the Sky intersects U.S. Highway 163 at a point 10 miles northwest of Moab, or 21 miles southeast of Crescent Junction on Interstate Highway 70. From U.S. 163 a paved road climbs colorful Sevenmile Canyon past sandstone cliffs of the Wingate, Kayenta, and Navajo Formations to reach the high mesa. There, just “offshore” to the north, are anchored the “battleships” that guard the island—Merrimac and Monitor Buttes ([fig. 12]). These landmarks are composed of the Entrada Sandstone—the same rock that forms Church Rock at the entrance to the Needles district ([fig. 37]) and that shapes the spectacular arches in Arches National Park. All three members of the Entrada (Wright and others, 1962), as noted in the [figure 12] caption, are present here as well as at Church Rock. Eleven miles from the junction with U.S. Highway 163 a graded road to the right, called Horsethief Trail, goes 16 miles down to the Green River, where it connects with roads following the river both upstream and downstream. The road upstream leads to two uranium mines in the lower part of Mineral Canyon which were reactivated in 1972 and 1973. The switchbacks are quite spectacular and are reminiscent of the Shafer Trail. Three miles south of the Horsethief Trail turnoff is a fork in the road—to the left the pavement continues to Dead Horse Point, and straight ahead a graded road leads southward to the Island in the Sky district of Canyonlands National Park.
MERRIMAC (LEFT) AND MONITOR BUTTES guard north entrance to Island in the Sky. White rock near middle is Navajo Sandstone. Buttes comprise all three members of Entrada Sandstone: remnant white top of Moab Member, vertical cliffs of Slick Rock Member, and sloping base of Dewey Bridge Member. (Fig. 12)
Most of Island in the Sky has a scattered growth of piñon and juniper trees, but several large flat areas, such as Grays Pasture, contain sufficient sandy soil to support a mantle of grass and weeds, which is used for grazing; however, grazing in this part of the park will be discontinued in 1975.