ACROSS PINNACLE PASS.
The morning after reaching Camp 12 dawned gloriously bright. The night had been cold, and a heavy frost had silenced every rill from the snow-slopes above. The clear, bracing air gave us renewed energy and a firmer desire to press on. Mr. Kerr and myself made an excursion ahead, while Lindsley and Crumback brought up a load of supplies from the cache left on the glacier below Camp 11.
On gaining the center of the Marvine glacier we had a magnificent view down the broad ice-stream, bordered on either hand by towering, snow-laden precipices, and changing, as the eye followed the downward slope, from pure white to brown and black in the distance. Far below we could barely discern the wooded summit of Blossom island, beyond which stretched the seemingly limitless ice-fields of the Malaspina glacier. All about us the white slope reflected the sunlight with painful brilliancy, while the black moraines and forests below and the mists over the distant ocean, made it seem as if one was looking down into a lower and darker world.
As we advanced toward the head of the glacier we found, as on several subsequent occasions, that the nearer we approached the sources of an ice-stream the easier our progress became. Following up the center of the glacier, we learned that it curved toward the east; and after an hour or two of weary tramping we reached the great amphitheatre in which it has its source. All about us were rugged mountain slopes, heavily loaded with snow, and forming clear white cliffs from which avalanches had descended. To the westward the wall of the amphitheatre was broken, and it was apparent that we could cross its rim in that direction. Pressing onward up the gently ascending slope, we came at length to a gap in the mountains bordered on the north by a towering cliff fully a thousand feet high, and were rejoiced to find that the snow surface on the opposite side of the divide inclined westward with a grade as gentle as the one we had ascended. Looking far down the western snow-slope, we could see where it joined a large glacier flowing southward past the end of the great cliffs which extended westward from the divide. The glacier we saw in the valley below is designated on our map as the Seward glacier, in honor of William H. Seward, the former Secretary of State, who negotiated the purchase of Alaska for the United States.
The pass we named Pinnacle pass, on account of the many towering pinnacles overshadowing it. Its elevation is about four thousand feet, and at the summit it has a breadth of only two or three hundred feet. The snow on the divide is greatly crevassed, but a convenient snow-bridge enabled us to cross without difficulty. The crevasses increased in breadth with the advance of the season, and on returning from our mountain trip in September we had to climb up on the bordering cliff in order to pass the main crevasse at the summit. Some idea of the crevasses of this region may be obtained from the following figure, drawn from a photograph taken on the western side of Pinnacle pass, not far from the summit.
| FIGURE 5—Crevasses on Pinnacle Pass; from a Photograph. |
The cliff on the north of Pinnacle pass is really a huge fault-scarp of recent date, intersecting stratified shale, limestone, and conglomerate, with a few thin coal-seams. The strata dip toward the north at a high angle, and present their broken edges in the great cliff rising above the pass. The cliffs extend westward from the pass, and retain a nearly horizontal crest line, but increase in height and grandeur, owing to the downward grade of the glacier along their base. A mile to the westward their elevation is fully two thousand feet. The cliffs throughout are almost everywhere bare of snow and too steep and rugged to be scaled. They form a strongly drawn boundary line in the geology of the region, and furnish the key to the structure and geological character of an extended area. All the rocks to the southward are sandstone and shale belonging to a well-defined series, and differ materially from the rocks in the fault-scarp. I have called the rocks toward the south, the Yakutat system, and those exposed in the faces of the fault-scarp the Pinnacle system. Directly north of Pinnacle pass, and at the base of Mount Owen, the rocks of the Yakutat system are exposed, and from their position and association it is evident that they are younger than the Pinnacle system and belong above it. If these conclusions are sustained by future investigation, they will carry with them certain deductions which are among the most remarkable in geological history. On the crest of the Pinnacle pass cliffs I afterwards found strata containing fossil shells and leaves belonging to species still living. These records of animal and plant life show that not only were the rocks of the Pinnacle system deposited since living species of mollusks and plants came into existence, but that the Yakutat system is still more recent. More than this, the upheaval of the mountains, the formation of numerous fault-scarps, and the origin of the glaciers, have all occurred since Pliocene times.