U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY Areal Distribution, Thickness, Mass, Volume, and Grain Size of Tephra-Fall Deposits from the 1992 Eruptions of Crater Peak Vent, Mt. Spurr Volcano, Alaska Open-File Report 01–370 Inferred Caldera Rim Mt. Spurr Crater Peak o n O a b c l s e o r V v a a t k o s r a l y A U S S G G G S D - U A F / G I - A The Alaska Volcano Observatory (AVO) was established in 1988 to monitor dangerous volcanoes, issue eruption alerts, assess volcano hazards, and conduct volcano research in Alaska. The cooperating agencies of AVO are the U.S. Geological Survey (USGS), the University of Alaska Fairbanks Geophysical Institute (UAFGI), and the Alaska Division of Geological and Geophysical Surveys (ADGGS). AVO also plays a key role in notification and tracking eruptions on the Kamchatka Peninsula of the Russian Far East as part of a formal working relationship with the Kamchatkan Volcanic Eruptions Response Team. Cover photograph: Oblique aerial view from the southeast of Mount Spurr volcano and Crater Peak flank vent, which is the site of all late Holocene and historical eruptive activity at this volcanic center. Photograph by Austin Post, September 4, 1996. Areal Distribution, Thickness, Mass, Volume, and Grain Size of Tephra-Fall Deposits from the 1992 Eruptions of Crater Peak Vent, Mt. Spurr Volcano, Alaska By Robert G. McGimsey1, Christina A. Neal1, and Colleen M. Riley2 Open-File Report 01-370 U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY Alaska Volcano Observatory Anchorage, Alaska 2001 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards (or with the North American Stratigraphic Code). Any use of trade, product or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 1U.S. Geological Survey, Anchorage, Alaska, 99508 2Michigan Technological University, Dept. of Geological and Engineering Sciences, Houghton, MI, 49931 U.S. DEPARTMENT OF THE INTERIOR GALE A. NORTON, Secretary U.S. GEOLOGICAL SURVEY CHARLES G. GROAT, Director This report, including maps and data tables, is also available for viewing and downloading at website http://geopubs.wr.usgs.gov/open-file/of01-370. How to contact the Alaska Volcano Observatory: U.S. Geological Survey 4200 University Drive Anchorage, AK 99508 (Tel. 907-786-7497) (Fax 907-786-7425) (Internet: http://www.avo.alaska.edu) CONTENTS Abstract.................................................................................................................................................................................. 1 Acknowledgements................................................................................................................................................................ 1 Introduction............................................................................................................................................................................ 2 Methods ................................................................................................................................................................................. 2 June 27 tephra-fall deposit..................................................................................................................................................... 3 August 18 tephra-fall deposit................................................................................................................................................. 4 September 16-17 tephra-fall deposit...................................................................................................................................... 5 References cited..................................................................................................................................................................... 6 Figures ................................................................................................................................................................................... 9 Tables..................................................................................................................................................................................... 33 PLATES 1. Map showing areal distribution of the June 27, 1992, tephra-fall deposit.............................................. [Attached] 2. Map showing areal and mass distribution of August 18 tephra-fall deposit........................................... [Attached] 3. Map showing areal distribution of September 16-17 tephra-fall deposit................................................ [Attached] FIGURES 1. Map of south-cnetral Alaska showing approximate areas of tephra deposition from ash plumes generated from each of the three 1992 eruptions of Mt. Spurr volcano .................................................................................................. 9 2. Index map showing the location of Mt. Spurr and the other histoically active volcanoes of the Aluetian Arc .... 10 3. Photograph of Crater Peak vent summit of Mt. Spurr .......................................................................................... 11 4. Photograph of collection of measured-area tephra samples from snowpack......................................................... 12 5. Photograph of collection of measured-area tephra samples from hard surfaces in areas below snowline ............ 13 6. Oblique photograph of northward aerial view of Mt.Spurr ................................................................................... 114 7. Plume trajectory forecast for 7:00am Alaska Daylight Time on June 27, 1992 ....................................................15 8. Map showing areal distribution of the June 27, 1992, tephra-fall deposit............................................................. 16 9. Graphs showing tephra-fall deposit thickness ....................................................................................................... 17 10. Photograph of August 18, 1992, eruption column from Crater Peak vent............................................................. 18 11. Map showing areal and mass distribution of August 18, tephra-fall deposit......................................................... 19 12. Grain-size plots for selected samples from the August Mt. Spurr tephra-fall deposit........................................... 20 13. Plume trajectory forecast for 7:00pm Alaska Daylight Time on August 18, 1992................................................ 21 14. Photograph of car in Anchorage covered with 3mm of fine sand-sized ash.......................................................... 22 FIGURES—Continued 15. Plume trajectory forecast for 1:00am Alaska Daylight Time on September 17, 1992 .......................................... 23 16. Map showing areal distribution of September 16-17 tephra-fall deposit............................................................... 24 17. Grain-size plots for selected samples from the September Mt. Spurr tephra-fall deposit ..................................... 25 TABLES 1. Mass-per-unit area measurements of June 27, 1992 .............................................................................................. 26 2. Latitude and longitude locations for June measured-area samples shown in Table 1 and on Figure 8................. 27 3. Measured-area samples of August 18, 1992, Mt. Spurr tephra.............................................................................. 28 4. Latitude and longitude locations for August measured-area samples shown in Table 3 and on Figure 11........... 29 5. Mass-per-unit-area measurements of September 16-17, 1992, Mt. Spurr tephra .................................................. 30 6. Latitude and longitude locations for September measusred-area samples shown in Table 5 and on Figure 16.... 31 7. Summary of mass, dense-rock volume, and bulk volume of tephra-fall deposits ................................................. 32 CONVERSION FACTORS and VERTICAL DATUM Multiply by To obtain millimeter (mm) 0.03937 inch centimeter (cm) 0.3937 inch meter (m) 3.281 foot kilometer (km) 0.6214 mile square kilometer (km2) 0.3861 square mile cubic meter (m3) 35.31 cubic foot cubic kilometer (km3) 0.2399 cubic mile meter per second (m/s) 3.281 foot per second meter per second (m/s) 2.237 mile per hour kilometer per hour (km/h) 0.6214 mile per hour cubic meter per second (m3/s) 35.31 cubic foot per second meter per square second (m/s2) 3.281 foot per square second In this report, temperature is reported in degrees Celsius (°C), which can be converted to degrees Fahrenheit (°F) by the equation °F = (1.8 X °C) + 32) Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929, formerly called “Sea-Level Datum of 1929”), which is derived from a general adjustment of the first-order leveling networks of the United States and Canada. Areal Distribution, Thickness, Mass, Volume, and Grain Size of Tephra-Fall Deposits from the 1992 Eruptions of Crater Peak Vent, Mt. Spurr Volcano, Alaska By Robert G. McGimsey, Christina A. Neal, and Colleen M.Riley ABSTRACT The Crater Peak flank vent of Mount Spurr volcano erupted June 27, August 18, and September 16- 17, 1992. The three eruptions were similar in intensity (vulcanian to subplinian eruption columns reach- ing up to 14 km Above Sea Level) and duration (3.5 to 4.0 hours) and produced tephra-fall deposits (12, 14, 15 x 106 m3 Dense Rock Equivalent [DRE])