The Geologic Story of Arches National Park 10

The Geologic Story of Arches National Park 10

About 1 mile farther northwest is a parking area (stop 23) from which a

short walk to the north end of Fiery Furnace leads to a narrow slot

between high fins (fig. 45), along which a short sandy trail leads to a

recess along the southwest wall containing Sand Dune Arch (fig. 46).

This hidden arch receives sunshine only near the middle of the day and

is a delightful, shady place to rest.

 

From the entrance to the slot leading to Sand Dune Arch, a trail goes

half a mile north across an open field to Broken Arch, shown in figure

16. This field, which separates the Fiery Furnace and Devils Garden

areas, is seen from the air in figure 12.

 

[Illustration: Petroglyph figure]

 

[Illustration: FIERY FURNACE, viewed northwest along park road about

1 mile northwest from stop 20. Fins and spires are of the jointed

Slick Rock Member (fig. 12), but the top of the Dewey Bridge Member

is seen to the right of the curve in the road. (Fig. 44)]

 

[Illustration: TRAIL TO SAND DUNE ARCH, looking northwest away from

arch, between towering fins of Slick Rock Member, at northwest end

of Fiery Furnace. Southeast end of Devils Garden in distance. (Fig.

45)]

 

[Illustration: SAND DUNE ARCH, in recess along southwest wall of

narrow slot shown in figure 45. Slick Rock Member. (Fig. 46)]

 

 

Salt Valley and Klondike Bluffs

 

Before proceeding to the end of the paved road, let us take an

unimproved side road, which turns south about a third of a mile beyond

the last stop, in order to see more of Salt Valley and to visit Klondike

Bluffs in the northwestern part of the park. After descending 2.3 miles

of winding road we reach the normally dry bed of Salt Valley Wash, and

turn abruptly to the northwest. For the next three-fourths of a mile the

“road” is simply two tracks in the loose, sandy bed of the wash, which

obviously should not be travelled when flooded or when there is even a

hint of rain. In dry weather, however, this road may be travelled by

ordinary passenger car. This stretch of the wash cuts through an

intruded block of the Paradox Member of the Hermosa Formation consisting

mainly of gray and brown gypsum, the common salt having been dissolved

out by ground water. Such an intrusive block of salt-bearing rock is

known to geologists as a diapir—not to be confused with the garment

(diaper) worn by infants.

 

From here on the road traverses a rather uninteresting stretch of valley

north of Salt Valley Wash. Eleven miles from the starting point, the

road reaches an intersection from which a side road leads southwestward

three-fourths of a mile to a parking area at the foot of Klondike

Bluffs, which form the south side of Salt Valley. From here, one may

make a strenuous hike over a primitive trail about 1½ miles long to

beautiful Tower Arch (fig. 47).

 

The valley road continues northwestward from the intersection to and

beyond the northwest end of the park and connects with roads to Crescent

Junction, Thompson, and the Yellow Cat mining district, north of the

park (p. 14).

 

Let us return to the paved road and continue our tour of the park.

 

 

Devils Garden

 

Turning left (northwest) at the intersection with the paved park road,

we enter Devils Garden—another large maze of towering red fins separated

by narrow slots, which resembles the Fiery Furnace. After a third of a

mile, we reach stop 24 and walk 100 feet or more to the north for a good

view of Skyline Arch (fig. 48). This arch is very appropriately named,

as it forms the skyline viewed either from the road on the south or from

the campground on the north, from points south of the amphitheater. Less

well known is the fact that Skyline Arch is clearly visible to the naked

eye or through binoculars from stretches of Highway I-70 (or old U.S.

Highways 6 and 50) about 11 miles to the north. Most arches and other

erosion forms do not change appearance much from day to day or year to

year, but some, like “Baby Arch” (fig. 15), show evidence of relatively

recent origin. In November 1940 (Abbey, 1971, p. 42) Skyline Arch

suddenly doubled in size by the fall of a large rock that occupied what

is now the northwest half of the arch. Photographs taken before and

after this event appear on pages 24 and 25 of the road guide and also in

the museum at the Visitor Center.

 

[Illustration: TOWER ARCH, on Klondike Bluffs, viewed eastward. Arch

is in Slick Rock Member but tower on left, after which arch was

named, is capped by a protective layer of the resistant Moab Member.

Opening is 88 feet wide and 43 feet high. Photograph by Robert D.

Miller. (Fig. 47)]

 

[Illustration: SKYLINE ARCH, viewed north from point about 100 feet

north of stop 24, in Slick Rock Member. Although fins are vertical,

note that the strata seem to dip about 15° to the right, although

the actual dip is to the northeast. (See fig. 50.) (Fig. 48)]

 

Another half mile brings us to a one-way (to right) loop at the end of

the park road. Just beyond the beginning of the loop is a parking lot

and very attractive picnic area containing several picnic tables shaded

by piñon pines at the foot of a towering red fin of the Slick Rock

Member. Just north of this picnic ground, a paved side road leads

eastward into a truly beautiful, well-equipped campground comprising

both back-in and drive-through campsites for trailers, campers, or

tents; three pairs of modern restrooms, hydrants, and drinking

fountains; and an amphitheater, where illustrated campfire talks are

given nightly during the summer. The east end of the campground is shown

in figure 49.

 

[Illustration: CAMPGROUND IN DEVILS GARDEN, viewed northwestward

across turn-around at southeastern end. (Fig. 49)]

 

Devils Garden in general and the campground in particular are on the

crest of a ridge separating Salt Valley to the southwest from the Sagers

Wash syncline to the northeast, which lies north of Yellow Cat Flat and

north of the area shown in figure 1. From the higher parts of the

campground striking views are to be had toward the north and northeast,

particularly late in the afternoon, as shown in figure 50.

 

[Illustration: VIEW NORTH FROM CAMPGROUND, in late afternoon.

Reddish Slick Rock Member capped by light-colored Moab Member are

seen dipping northeastward toward Sagers Wash syncline. Book Cliffs,

north of Thompson, are 16 miles north on left skyline. (Fig. 50)]

 

In about the middle of the one-way loop at the end of the park road is a

well that supplies water to the campground from early in the spring

until the return of freezing weather late in the fall. The well, which

was drilled in 1962 to a depth of 900 feet, obtains a small amount of

water from the Wingate Sandstone. No water was found in the overlying

Navajo and Entrada Sandstones because of the pronounced dip of the rocks

toward the northeast, which allows any water in these rocks to drain

northeastward (Ted Arnow, written commun., 1963). Water from this well

is pumped to a steel tank in a high part of the campground, whence it

flows by gravity to the three sets of restrooms.

 

[Illustration: SOUTHEASTERN PART OF DEVILS GARDEN TRAIL, viewed

northwestward. Narrow slot between fins of Slick Rock Member

indicates local spacing of joints. (Fig. 51)]

 

At the northwest end of the one-way loop is a large parking area for use

by people hiking the Devils Garden trail. This trail leads to seven of

the most interesting arches in the park, all of which are in the Slick

Rock Member, and there are many more farther to the northwest. The

approximate distances to the seven arches are given in the paragraphs

that follow. The trail is paved for about 1 mile as far as Landscape

Arch (fig. 53), but from there to Double O Arch (fig. 56) the trail is

primitive, and the Park Service recommends rubber soles as part of the

trail is on bare sandstone. For these reasons, many visitors hike only

as far as Landscape Arch.

 

[Illustration: PINE TREE ARCH, viewed northeastward. Opening is 46

feet wide and 48 feet high. Fin is 30 feet thick. (Fig. 52)]

 

Much of the trail, particularly the first part, lies in a narrow slot

between fins of the Slick Rock Member, as shown in figure 51. After

about half a mile, a side trail to the north leads to a Y, the

right-hand fork of which goes to Tunnel Arch (fig. 14). The left-hand

fork leads to Pine Tree Arch, obviously named for the piñon pine framed

by this arch (fig. 52).

 

At the end of the improved part of the trail, we reach Landscape Arch

(fig. 53), claimed by the Park Service to be the longest known natural

arch in the world. According to Ouellette (1958) it is 291 feet long and

118 feet high, but Professor Stevens’ measurements indicate it to be 287

feet long and 106 feet high. At its thinnest point on the right, the

span is only 11 feet wide and 11 feet thick. In 1958 three young men

made what was claimed to be the second known ascent of Landscape Arch,

using ropes and other climbing gear, after which they walked across

(Ouellette, 1958). This crossing was made with the permission of a park

ranger, but such permission is no longer given, for the safety of both

the arch and of would-be climbers.

 

Wall Arch is about a quarter of a mile beyond the end of the improved

part of the trail, and another three-fourths mile brings us to Navajo

Arch (fig. 54) and Partition Arch (fig. 55). A distant view of Partition

Arch may be had just before reaching Landscape Arch. Part of the

remaining trail to Double O Arch (fig. 56) is on the top of a low

sandstone fin, in part between somewhat higher fins and in part above

lower slots.

 

[Illustration: LANDSCAPE ARCH, viewed southwestward from near end of

improved part of Devils Garden trail. Note that ground beneath arch

is covered by slope wash and near the middle with what appears to be

a small landslide. Slick Rock Member here is more nearly buff than

salmon colored, because of a smaller content of iron oxide. Fresh

breaks and angular blocks of stone at right abutment indicate

relatively recent rock falls. See text for size. (Fig. 53)]

 

[Illustration: NAVAJO ARCH, viewed northeastward from a branch of

Devils Garden trail. One of few arches having a flat soil-covered

floor. Opening is 40½ feet wide. Photograph by National Park

Service. (Fig. 54)]

 

Beautiful Double O Arch (fig. 56) is at the end of the Devils Garden

trail about 2½ miles northwest of the trailhead. About half a mile

northwest of the trail’s end is a prominent landmark called Dark Angel

(fig. 57), which is visible in figure 12 and from the unimproved road in

Salt Valley.

 

[Illustration: PARTITION ARCH, viewed southwestward from near Devils

Garden trail. Arch frames part of south wall of Salt Valley and, on

skyline, mesas south of Moab Valley. Opening is 27½ feet wide and 26

feet high. A smaller opening to the right measures 8½ feet wide and 8 feet high. Photograph by Dawn E. Reed. (Fig. 55)]