00100	Introduction
00200	
00300	This paper is a geological study of the  Mt. Katmai
00400	area. Mt. Katmai is located on the southeasternmost 
00500	portion of the Alaska Peninsula (fig. 1).The area
00600	contains an approximate linear array or chain of 12 volcanoes
00700	. A northeasterly trending asymeteric plunging anticline
00800	disects many of the volcanoes, while Mt. Katmai 
00900	itself lies a few miles to the southeast.
01000	The most recent event was in 1968 when Mt. Trident 
01100	erupted. The ara
01200	erupted. The area is very active volcanicaly,
01300	infact 15 eruptions have been recorded since 1700;
01400	Mt. Katmai having 7, the last eruption was in 1931. The
01500	elevations of Mts. Katmai and Trident are 7540 and 6830
01600	feet respectfully. The volcanics cover at least 7000-
01700	9000 feet of relitivly undistorted marine sedimentsof 
01800	Upper Jurassic age. These include for the most 
01900	part; a basal unit of pebble to boulder conglomerate
02000	overlain by layers of sandstone, shale, and siltstone.
02100	Volcanism began atleast by Early Eocene time and 
02200	continued more or less 
02300	throughout the Tertairy and Quaternary. These units
02400	and their relationships will be described in somewhat 
02500	more detail later.
02600	
02700	Regional Geologic Setting
02800	
02900	Mt. Katmai is part of a great 
03000	island arc system that extends westward from the Alaska
03100	Peninsula to the Kamchatka Peninsula,a distance of 
03200	some      miles. Formed by the subduction of the 
03300	North Pacific oceanic lithosphere, the island arc is 
03400	tectonicly active, exemplified by numerous
03500	volcanoes and a high level of siesmic activity. Earthquake
03600	foci, when ploted, seem to be confined to the 
03700	Beneoff zone which forms a 30 degree slope
03800	away from the trench and terminates at about the northern
03900	extension of the Aleution chain.
04000	This suggests melting of the subducted plate along the
04100	lower portion of the Beneoff zone , but
04200	well within the crust. (fig. 2). 
04300	Acidic lavas are more typical of island arc systems.
04400	It has been suggested that the subducted sediments
04500	deposited in the trench as well as partial melting of the
04600	overlying granitic rock. However, Hathorn and Dikinson
04700	(1969) suggest the acidic magmas are formed at the 
04800	Beneoff zone and are not the result of remelting
04900	of the overlying crust. Obviously much work is needed in
05000	the area of magmatic chambers.
05100	
05200	Ahistory of volcanism can be corralated to 
05300	magnetic anomalies (Grow and Atwater 1970) suggesting
05400	the volcanic activity isproportional to the rate at ahich 
05500	the plate is being subducted. And that the present 
05600	reduction of volcanic activity in the central Aleutions
05700	is the result of the reduction of plate movement with 
05800	respect to each other.