I DEPARTMENT OF THE INTERIOR J Hubert Work.Secretary U. & GEOLOGICAL SURVEY -- IAKCHAK CRATER, ALASKA PENINSULA BY WALTER R. SMITH Publlsbed Map 15,1925 Shorter contributions to general geology, 1923-1924 (*es 139-145) - - I. WASHINGTON ILLUSTRATIONS. psga PLATEXLI. Aniakchak Crater, Alaska Peninsula ............................................... 140 XLII. Relief map of Aniakchak Crater and vicinity, Alaska Peninsula ....................... 140 XLIII. A, B, Exposures of volcanic ash on Ray Creek, Alaska Peninsula; C, "The Gates" of Aniak- chak Crater, Alaska Peninsula ................................ 140 XLIV. A, Black Nose, Alaska Peninsula; B, Mount Chiginagak, Alaska Peninsula ------------ 140 FIGURE11. Sketch map ahowing location of Aniakchak Crater, Alaska Peninsula -------_---------- 140 I1 ANIAKCHAK CRATER, ALASKA PENINSULA. The discovery of a gigantic crater north- the deposits of volcanicash became more numer- west of Aniakchsk Bay (see fig. 11) closes ous and the materialcoarser. Along Ray Creek, what had been thaught to be a wide gap in the 18% miles from the crater, pieces of scoria and extensive series bf 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 P1. XLIII, A, B.) The floor of the broad active and recently active volcanoes than in all valley of Cinder River was found to '~eentirely 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 occupied 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, however, 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.' 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 theiraactivity 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. Aniakchak 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, SII)was dis- "The Gates" (PI. XLIII, C), from two long, covered in August, 1922,= 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 reconnaissance topographic and geologic survey crater is nearly circular in outline and has a of the country west of the Aleutian Mountains maximum diameter of 6 % miles and a minimum diameter of a little over 594 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 di8trict 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 U. S. Qeol. Survey Water- truncated cinder cone, the summit of which is Supply Paper 41% pl. I, 1917 2,200 feet above Surprise Lake, occupies the W. French, an engineer, but no report of the dis- south-central part of the area inclosed within the crater rim. 140 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1923-1924. The crater was fist mentioned without a report ' on the geology of the district. In a name by R. F. Griggs in a book that was chronologic account of observed volcanic ao- printed shortly after the return of Mr. Sar- tivity in Alaska, Grewingk gives the geo- gent's party. Under the name "Old Crater" graphic position of Veniaminof volcano as its position is indicated On the map of Alaska I 4 s,,,ith. W. R.. snd Baker, A. A,, The cold ~ay-~hignikdistrict: published by the Survey in 1923. U. 8. a&.~urve; BUU. 755, p. 157, 1924. 8 Qrewingk, Constanti, Beitdge zur Kentniss der orographischen description of the crater Was ,,, ~~mmt~henBaschaflenheit der ~ord-westKuste Amerikas, ~.- .~ I 2;den anliegenden Inseln (with geologic and other maps), St. Peters- 8 The Valley of Ten Thousand Smokes, p. 85. footnote, 1022. 1 burg, 1850. ZT. S. GEOLOGICSL SURTEY PROFESSIONAL PAPER 132 PLATE XLI AArIA1iCIIhl< CIL4TEK. ALASIC-4 PENINSULA U. S. GEOLOGICAL SLTRVEY PROFESSIONAL PAPER 132 PLATE XLII U. 8. DEOLOCICAL SURVEY PROFESSIONAL PAPER 132 PLATE XLIII I( A, B. EXl'0SIJFIl~:S OF VOLCANIC Aslr 0'4 R4Y CREI.:K, ALASKA PENINSULA U. R. GEOI>OGICAL SURTEP PROFESSIONAL PAPER 172 PL4TE XLIV I 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 I 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 I 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 inhabitant? of noted except for several talus slopes in the Ch.lgnrk, the nearest settlement, and of local canyon of Aniakchak ~ivirand 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 made by the writer during a few hours. places-the sharp notch through which Aniak- chak River flows and a depression on the west Time was not avdable to determine the age of 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 I sea level and 3,000 feet above Surprise Lake. of rather gentle peaks which are separated from 1 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.