u.s. Geological Survey Bulletin 2072 AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY Instructions on ordering publications of the U.S. Geological Survey, along with prices of the last offerings, are given in the current­ year issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Survey publications released prior to the current year are listed in the most recent annual "Price and Availability List." Publications that are listed in various U.S. Geological Survey catalogs (see back inside cover) but not listed in the most recent annual "Price and Availability List" are no longer available. Reports released through the NTIS may be obtained by writing to the National Technical Information Service, U.S. Department of Commerce, Springfield, VA 22161; please include NTIS report number with inquiry. Order U.S. Geological Survey publications by mail or over the counter from the offices given below. BY MAIL OVER THE COUNTER Books Books and Maps Professional Papers, Bulletins, Water-Supply Papers, Tech­ Books and maps of the U.S. Geological Survey are available niques of Water-Resources Investigations, Circulars, publications over the counter at the following U.S. Geological Survey offices, of general interest (such as leaflets, pamphlets, booklets), single all of which are authorized agents of the Superintendent of Docu­ copies of Earthquakes & Volcanoes, Preliminary Determination of ments. Epicenters, and some miscellaneous reports, including some of the foregoing series that have gone out of print at the Superin­ • ANCHORAGE, Alaska-4230 University Dr., Rm. 101 tendent of Documents, are obtainable by mail from • LAKEWOOD, Colorado-Federal Center, Bldg. 810 U.S. Geological Survey, Information Services Box 25286, Federal Center • MENLO PARK, California-Bldg. 3, Rm. 3128, 345 Mid­ Denver, CO 80225 dlefield Rd. 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Maps Maps Only For maps, address mail orders to Maps may be purchased over the counter at the U.S. Geologi­ U.S. Geological Survey, Map Distribution cal Survey offices: Box 25286, Bldg. 810, Federal Center Denver, CO 80225 • FAIRBANKS, Alaska-New Federal Building, 101 Twelfth Ave. Residents of Alaska may order maps from U.S. Geological Survey, Earth Science Information Center • ROLLA, Missouri-1400 Independence Rd. 1011\velfth Ave., Box 12 Fairbanks, AK 99701 • STENNIS SPACE CENTER, Mississippi-Bldg. 3101 VOLCANOES OF THE WESTERN WRANGELL MOUNTAIN, ALASKA-WRANGELL-ST. ELIAS NATIONAL PARK AND PRESERVE Frontispiece. Mount Wrangell from near Tonsina (about no, and a prominent steam plume rises from one of the 20 mi south of Copper Center), probably during summer summit craters. Mount Zanetti, a large cinder cone on 1902. Dark ash, apparently from phreatic eruptions, the north flank of Mount Wrangell, is at left. Photograph blankets the ice- and snow-covered surface of the volca- by We. Mendenhall, U.S. Geological Survey. Guide to the Volcanoes of the Western Wrangell Mountains, Alaska-Wrangell-St. Elias National Park and Preserve By Donald H. Richter, Danny S. Rosenkrans, and Margaret J. Steigerwald U.S. GEOLOGICAL SURVEY BULLETIN 2072 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1995 I ·1 I I u.s. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary u.s. GEOLOGICAL SURVEY Gordon P. Eaton, Director For sale by U.S. Geological Survey, Information Services Box 25286, Federal Center Denver, CO 80225 Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. Text and illustrations edited by George A. Havach Graphics prepared by Michele Coveau Book design and layout by Linnea Larsen Library of Congress Cataloging-in-Publication Data Richter, Donald H. Guide to the volcanoes of the western Wrangell Mountains, Alaska: Wrangell-St. Elias National Park and Preserve I by Donald H. Richter, Danny S. Rosenkrans, and Margaret J. Steigelwald p. em. - (U.S. Geological Survey bulletin; 2072) Includes bibliographical references. Supt. of Docs. no.: I 19.3:2072 1. Volcanoes-Alaska-Wrangell Mountains. I. Rosenkrans, Danny S. II. Steigerwald, Margaret J. III. Title. IV. Series. QE75.B9 no. 2072 [QE524] 557.3 s-dc20 94-32571 [551.2'1 '097983] CIP Cover. The massive, ice-covered face of Mount Sanford. View westward across West Glacier. Photograph by D. Rosenkrans, 1984. CONTENTS Introduction 1 Early history and geologic exploration....................................................................... I A national park in the Wrangells 3 Geologic background 3 Volcanoes and plate tectonics 3 The Wrangell volcanoes ,................................................... 7 How did they form? 7 How old are they?............................................................................................... 8 How tall are they?.............................................................................................. 10 How do they compare with other mountains?..................................................... 10 Descriptions ofindividual volcanoes 10 Mount Wrangell 10 Mount Drum............................................................................................. 13 Mount Sanford 16 Capital Mountain...................................................................................... 18 Tanada Peak. 20 Mount Jarvis............................................................................................. 21 Skookum Creek Volcano.......................................................................... 22 Mount Blackburn 24 Boomerang Volcano................................................................................. 25 Mount Gordon.......................................................................................... 25 White River Ash.......................................................................................................... 27 Mud volcanoes 29 Acknowledgments 29 Selected references..... 30 FIGURES 1. South-central Alaska and part of the Yukon Territory, Canada, showing early exploration routes of Allen in 1885 and Schwatka and Hayes in 1891 and route of the Cordova-Kennicott Railroad that was used from 1911 to 1938 2 2. South-central Alaska and part of the Yukon Territory, Canada, showing Wrangell volcanic field and some major geologic features......................................................................................................................................... 4 3. Western North America, showing present position of Wrangellia composite terrane and its probable position 250 million years ago, before it moved northward as part of an ancient Pacific plate........ 5 4. Major crustal plates of the world 5 5. Diagrammatic cross section through the Earth's crust and upper mantle, showing plate-tectonic features discussed in text.................................................................................................................................................... 6 6. Diagrammatic north-south cross sections through south-central Alaska and the northern Pacific Ocean, showing development of Wrangell volcanic field through subduction of the Pacific plate................................ 7 7. Wrangell Mountains and part of the St. Elias Mountains.................................................................................... 8 8. Diagrammatic cross section model illustrating development of a Wrangell volcano 9 9. Known periods of eruptive activity for radiometrically dated western Wrangell volcanoes.............................. 10 10. Comparative profiles of some Pacific-rim volcanoes........................................................................................... 11 11. Topographic and generalized geologic map of Mount Wrangell......................................................................... 12 12. Mount Wrangell from Willow Lake at mile 87 on the Richardson Highway..................................................... 12 V VI CONTENTS 13. Topographic and generalized geologic map of Mount Drum 14 14. Mount Drum from mile 1 on the Tok Cutoff of the Glenn Highway................................................................. 14 15. Mount Drum at sunset from Willow Lake at mile 87 on the Richardson Highway........................................... 15 16. Generalized geologic cross section through Mount Drum 16 17. Approximate extent of volcanic avalanche and mudflow deposits probably generated by late cataclysmic eruptions of Mount Drum..................................................................................................................................... 16 18. Topographic and generalized geologic map of Mount Sanford........................................................................... 17 19. Mount Sanford from the Gulkana Airport on the Richardson Highway............................................................. 18 20. Topographic and generalized geologic map of Capital Mountain......................................................................