Aniakchak Crater, Alaska Peninsula

ANIAKCHAK CRATER, ALASKA PENINSULA. By wALTER R. SMITH. The discovery or" a gigantic crater north the deposits of volcanic ash became more numer west of Aniakchak Bay (see fig. 11) closes ous and the material coarser. Along Ray Creek, what had been thought to be a wide gap in the 18 Y2 miles from the crater, pieces of scoria and extensive series of volcanoes occurring at fine ash had consolidated and subsequently irregular intervals for nearly 600 miles along been cut by the stream until vertical walls the axial line of the Alaska Peninsula and the stand 6 to 12 feet high on both banks. (See Aleutian Islands. In this belt there are more Pl. XLIII, A, B.) The floor of the broad active and recently active volcanoes than in all valley of Cinder River was found to be entirely the rest of North America. Exclusive of those covered by volcanic ejecta, but the source of on the west side of Cook Inlet, which, how the material was not discovered until the ever, belong to the same group, this belt con summit of Elephant Mountain was occupiljd tains at least 42 active or well-preserved by Mr. Sargent and the writer. Prior to the volcanoes and about half as many mountains view of the crater, h0wever, locations on the suspected or reported to be volcanoes. The topographic map of a group of peaks in the locations of some of these mountains and the distance had assumed the form of a circle, but hot springs on the Alaska Peninsula and the the reason of the . arrangement was not sus Aleutian Islands are shown on a map prepared pected. by G. A. Waring.1 Attention has been called Aniakchak Crater is 24 miles northwest of to these volcanoes for nearly two centuries, Aniakchak Bay, approximately in the central but a record of their activity since the dis part of the Alaska Peninsula, on the divide covery of Alaska is far from being complete, between the Pacific Ocean and Bering Sea. and an adequate description of them as a Although there are no trails, the district is group has never been written. Owing to easily accessible from either side of the penin-: their recent activity or unusual scenic beauty, sula. Ania.kchak River, the largest stream on some of the best known of the group are the peninsula flowing into the Pacific Ocean, Mounts Katmai, Bogoslof, and Shishaldin, rises within the crater and breaks through the but there are many other beautiful and in east side of the rim in a narrow and pictur teresting cones and craters. esquely castled canyon which has been named Aniakchak Crater (Pls. XLI, XLII) was dis " The Gates" (Pl. XLIII, 0), from two long, covered in August, 1922,2 by a United States nearly symmetrical mountain spurs that di Geological Survey party, in charge of R. H. Sar verge from the canyon, one on each side of the gent, topographic engineer, in the course of a river, and inclose the upper valley. The crater is nearly circular in outline and has a reconnaissance topographic and geologic survey maximum diameter of 6%' miles and a minimum of the country west of the Aleutian Mountains diameter of a little over 5%' miles. The lowest between Wide and Aniakchak bays. The first part of the crater floor is 1,100 feet above sea evidence of an ancient volcanic eruption in the level and contains Surprise ·Lake, a body of district was observed 30 miles northeast of the water with an area of 2 square miles. The crater, in the form of thin deposits of fine ash walls are well preserved and rise almost ver concentrated in small depressions on the hill tically in places to altitudes of 1,200 to 3,000 sides. As the work progressed southwestward feet above the bottom of the crater. A large 1 Waring, G. A., Mineral springs of Alaska: U.S. Geol. Survey Water truncated cinder cone, the SU¥J.mit of which is Supply Paper 418, pl. 1, 191'?. 2,200 feet above Surprise Lake, occupies the 2 It has recently been reported that W. W. French, an engineer, and party visited the crater in July, 1921, but no report of the dis south-central part of the area inclosed within covery was made at that time. the crater rim. 139 140 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1923-1924. The crater was first mentioned without a report 4 on the geology of the district. In a name by R. F. Griggs 3 in a book that was chronologie account of observed volcanic ac printed shortly after the return of Mr. Sar tivity in Alaska, Grewingk 5 gives the geo gent's party. Under the name "Old Crater" graphic position of V eniaminof volcano as N oO 0 c 1"' c1- f ~ Oi\=c::>===isi===:::::EIO:==:==:==:ii'IS====::::i20 Miles o Kak I. FIGURE 11.-Sketch map showing location of Aniakchak Crater, Alaska Peninsula. its position· is indicated on the map of Alaska • Smith, W. R., and Baker, A. A., The Cold Bay-Chignik district: published by the Survey in 1923. A very brief U.S. Geol. Survey Bull. 755, p. 157, 1924. 6 Grewingk, Constantin, Beitrage zur Kentniss der orographischen description of the crater was included 1n a und geognostischen Beschaffenheit der Nord-west Kuste Amerikas, mit den anliegenden Inseln (with geologic and other maps), St. Peters 3 The Valley of Ten Thousand Smokes, p. 65, footnote, 1922. burg, 1850. U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 132 PLATE XLI ANIAKCHAK CRATER, ALASKA PENINSULA U, S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 132 PLATE XLII RELIEF MAP OF ANIAKCHAK CRATER AND VICINITY, ALASKA PENINSULA U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 132 PLATE XLIII A B A, B. EXPOSURES OF VOLCANIC ASH ON RAY CREEK, ALASKA PENINSULA C. "THE GATES" OF ANIAKCHAK CRATER, ALASKA PENINSULA U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 132 PLATE XLIV A. BLACK NOSE, ALASKA PENINSULA B. MOUNT CHIGINAGAK, ALASKA PENINSULA ANIAKCHAK CRATER, ALASKA PENINSULA. 141 latitude 56° and longitude 158° to 159°. small cones near the upper end of the lake rise This position is rather close to that of Aniak about 200 feet above the floor of the crater. chak Crater, which is latitude 56° 45' and longi The summit of the large cinder cone is 4~ tude 158° 9', but from the short account given miles from the point at which the picture was it is quite evident that Grewingk meant the taken; the mountains beyond the cone are 6 volcano known at present as Veniaminof, lati miles from the observer. The inner wall is tude 56° 17' and longitude 159° 15', and not abrupt-at places nearly vertical-and so far Aniakchak Crater. Although the Russian as known it can not be easily descended except scientists and travelers recorded many inter just north of The Gates. A view of Black esting and valuable observations regarding the Nose (Pl. XLIV, A), the peak immediately volcanoes of Alaska Peninsula, they made no south of The Gates, taken from a cinder ridge mention, so far as known to the writer, of the within the crater, gives an idea of the steepness immense crater discovered in 1922. It is quite of parts of the inner wall. The south side of probable that some of the Russian fur hunters, the crater rim affords a gathering ground for or perhaps a prospector or trapper of more the snow, and here vigorous alpine glaciers recent days, came across the crater but either have been formed on the steep slopes. Evi failed to recognize it as such or failed to report dence of slumping along the inner wall was not it. Inquiries were made of the inhabitants of noted except for several talus slopes in the Chignik, the nearest settlement, and of local canyon 'bf Aniakchak River and near the base trappers, all of whom knew nothing about the of Black Nose. The circumference of the crater crater. The present paper is based on observa is nearly 19 miles. The rim is broken in two tions Inade by the writer during a few hours. places-the sharp notch through which Aniak Time was not available to determine the age of chak River flows and a depression on the west side which · was not seen in 1922 but has been the crater or the exact manner in which it was reported by M. W. Taylor, of Seattle, who formed. visited the crater in 1923. On the south side The observer at a distance would not suspect the highest point on the rim is 4,200 feet above the existence of a huge crater within the cluster sea level and 3,000 feet above Surprise Lake. of rather gentle peaks which are separated from This peak and several others close by were the other mountains of the district by broad obscured by clouds at the time the photograph level areas. The valleys of Meshik and Aniak reproduced in Plate XLIV was taken. The chak rivers west of the crater are in general greater part of the crest of the rim is not jagged, less than 200 feet above sea level. The boldest although Black Nose and several other sharp portion of the outer rim of the crater is along peaks rise above the average altitude, which is the east side of the mountains, where cliffs rise approximately 3,000 feet. abruptly from the tributary valleys of Aniak Along the north and northeast sides the inner chak and Meshik rivers. Over these precipi wall is partly covered by detritus, but in the tous cliffs many streams cascade from the few exposures seen the rocks appeared to be glaciers near the summit of the rim.

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