Cover-Ash billows from the vent of Mount St. Helens Volcano, 

Washington, during the catastrophic eruption which began at 8:32 a.m. on 

May 18, 1980. View looks to the northeast. USGS photograph taken about 

noon by Robert M. Krimmel. 
FIRST INTERNATIONAL 

SYMPOSIUM ON 

VOLCANIC ASH AND 

AVIATION SAFETY 

PROGRAM AND ABSTRACTS 

SEATTLE, WASHINGTON 

JULY 8-12, 1991 

Edited by THOMAS J. CASADEV ALL 

Sponsored by 

Air Line Pilots Association 

Air Transport Association of America 

Federal Aviation Administration 

National Oceanic and Atmospheric Administration 

U.S. Geological Survey 

Co-sponsored by 

Aerospace Industries Association of America 

American Institute of Aeronautics and Astronautics 

Flight Safety Foundation 

International Association of Volcanology and Chemistry of the Earth's Interior 

National Transportation Safety Board 

U.S. GEOLOGICAL SURVEY CIRCULAR 1065 
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

This report has not been reviewed for conformity with U.S. Geological Survey 

editorial standards. 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. 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1991 

Available from the 

Books and Open-File Reports Section 

U.S. Geological Survey 

Federal Center 

Box 25425 

Denver, CO 80225 
CONTENTS 

Symposium Organization iv 

Introduction 1 

Interest in the Ash Cloud Problem 1 

References Cited 3 

Acknowledgments 3 

Program 4 

Abstracts 11 

Authors' Address List 48 

Organizing Committee Addresses 58 

Contents iii 
ALPA 

ATA 

FAA 

NOAA 

USGS 

AlA 

IAVCEI 

FSF 

SYMPOSIUM ORGANIZATION 

Organizing Committee 

General Chairman: Donald D. Engen 

Edward Miller and William Phaneuf 

Donald Trombley, Helen Weston, and Genice Morgan 

Robert E. Machol and Nicholas Krull 

Michael Matson and Anthony Mostek 

Christopher G. Newhall (Chairman) and Thomas J. Casadevall 

John Amatetti and Zygmund J. Przedpelski 

Grant Heiken 

Allen K. Mears 

Program Committee 

Thomas J. Casadevall (USGS) 

Robert E. Machol (FAA) 

Michael Matson (NOAA) 

Field Trips 

Steven R. Brantley (USGS) 

iv Symposium Organization 
FIRST INTERNATIONAL SYMPOSIUM ON VOLCANIC ASH 

AND AVIATION SAFETY 

Thomas J. Casadevall, Editor 

INTRODUCTION 

Volcanic ash produced by the 1989-90 eruptions of 

Redoubt Volcano in Alaska widely affected commercial 

and military air operations in the vicinity of Anchorage 

(Brantley, 1990). These effects included damage to some 

jet aircraft, as well as indirect impacts to the Anchorage 

economy resulting from rerouting and cancellations of 

flight operations. 

Between December 1989 and February 1990, five 

commercial jetliners suffered damage from encounters 

with volcanic ash from Redoubt Volcano. The most 

serious incident occurred on December 15, 1989, when a 

new Boeing 747-400 aircraft encountered an ash cloud at 

a distance of 150 nautical miles northeast of the volcano 

as the jet was descending for a landing in Anchorage. 

While there were no injuries to passengers, the damage 

to engines, avionics, and aircraft structure from this 

encounter cost in excess of $80 million (Steenblik, 1990). 

Additional encounters between jet aircraft and volcanic 

ash clouds occurred on December 15 and 16, 1989 and 

February 21, 1990, but did not result in engine failure. 

During the days following the December 15-16 

incidents, Anchorage airport remained open; however, 

most airline companies cancelled operations for up to 

several days. Several international carriers cancelled or 

curtailed operations through January 1990 and normal 

service did not resume until mid-February. Impacts to 

military flight operations consisted mostly of 

cancellation of flights and rerouting of aircraft. The 

resulting loss of revenue from curtailed operations at 

Anchorage International Airport during several months 

following the eruption is estimated to total $2.6 million 

(Brantley, 1990). 

One outcome of the Redoubt incidents has been to 

increase interest in the issue of volcanic hazards and 

aviation safety among a broad group which includes 

commercial and military air operators, aircraft 

manufacturers, the Federal Aviation Administration, the 

National Weather Service, and the U.S. Geological 

Survey. To focus this interest, the First International 

Symposium on Volcanic Ash and Aviation Safety is 

being held in Seattle, Washington in July 1991. The 

AIMS of the symposium are: 1. to encourage 

improvements in the detection, tracking, and warning of 

volcanic ash hazard so that aircraft may avoid ash 

clouds; and 2. to review the effects of volcanic ash on 

aircraft so that pilots who encounter ash can respond 

appropriately. 

Technical sessions The response to the initial call for 

papers for the symposium was enthusiastic. Eightyeight abstracts have been submitted for presentations in 

Seattle. The symposium includes six principal topics: 

the Redoubt eruptions and their impacts; Volcanoes and 

Ash Clouds; Damage and Impacts; Communications and 

Procedures; Meteorology and Ash Cloud Modeling; and 

Detection and Tracking. About 30 papers will be 

presented orally in plenary session; the remainder will 

be presented in poster displays during technical session 

onJuly9-11, 1991. 

We will prepare a SYMPOSIUM PROCEEDINGS 

VOLUME to permanently record the papers and 

discussions held during the symposium. The volume 

will follow the same major headings as in the 

symposium and all presenters are requested to submit 

papers describing their presentations. 

Field trips The symposium will include two daylong field trips. On Monday, July 8, participants will 

visit the FAA Air Route Traffic Control Center in 

Auburn, Washington, and the Boeing Airplane Co. 

factory in Renton, Washington, where 737 and 757 

aircraft are manufactured. On Friday, July 12, 

participants will visit the Mount St. Helens Volcanic 

Monument. The May 18, 1980, eruption of Mount St. 

Helens was the most costly volcanic eruption in U.S. 

History. This tour provides an opportunity to view the 

devastation caused by the eruption and to see the lava 

dome, which has grown within the 1980 crater. 

INTEREST IN THE ASH CLOUD HAZARD 

Volcanic ash clouds are very difficult to detect by 

aircraft during flight using onboard sensors and current 

technology. Development of new sensor technology is 

currently underway, especially in Australia. The 

greatest success to date in mitigating the ash cloud 

hazard has come through the combined efforts of 

ground-based observers, pilots, meteorologists, and airtraffic-management agencies working together to 

provide early warning to aircraft. 

Volcanic Ash and Aviation Safety 
The problem of volcanic hazards to aviation safety 

came to wide public attention when several jet aircraft 

suffered damage after flying through volcanic ash 

clouds from the 1980 eruptions of Mount St. Helens 

volcano, Washington. Interest in the problem grew 

rapidly in the early 1980's following several near-fatal 

encounters of jumbo-jet aircraft with ash-rich eruption 

clouds that had traveled considerable distances from 

their sources. In 1982, two incidents occurred within 3 

weeks of each other when Boeing 747-200 passenger jets 

encountered ash from two separate eruptions of 

Galunggung Volcano in Java, Indonesia (Smith, 1983). 

In both cases, volcanic ash entered the jet engines and 

caused thrust loss of all four engines. After powerless 

descents of nearly 25,000 feet, the pilots of both aircraft 

restarted their engines and landed safely at Jakarta 

Airport although both aircraft suffered extensive 

damage to engines and exterior surfaces. Other 

eruptions during the decade in Indonesia, Japan, Italy, 

and the United States also led to damaging encounters. 

Redoubt Volcano emits a vigorous plume of water vapor, sulfur dioxide, 

and carbon dioxide during a period of quiescent degassing between explosive 

eruptions. The plume is drifting to the west. View is to the north. Plumes 

2 Volcanic Ash and Aviation Safety 

These encounters triggered international efforts to 

evaluate and address the problem of volcanic hazards to 

aviation safety. In 1982, a Volcanic Ash Warnings Group 

(VA W) group was organized under leadership of the 

International Civil Aviation Organization (ICAO) in 

Montreal, and the Airways Volcano Watch was created by 

the Australian Department of Aviation. A May 1985 

encounter between a 747-200 and an ash cloud from 

Soputan Volcano in Sulawesi, Indonesia, prompted the 

Indonesian and Australian governments to form a 

Volcanological/ Airspace Liaison Committee (VULCAN) 

to improve communications about volcanic eruptions in 

the Indonesian region. In 1988, ICAO member states 

adopted a set of amendments to ICAO regulations for an 

International Airways Volcano Watch to provide alerts 

from eruptive activity worldwide. ICAO efforts 

included development of a special form of pilot report 

(PIREP) for reporting volcanic events (Fox, 1988). 

such as this are described in the paper by P. V. Hobbs, L. F. Radke, and D. J. 

Coffman. Photograph by Steven R. Brantley on January 22, 1990. 
Also in 1988, the World Organization of Volcano 

Observatories (WOVO), in cooperation with ICAO and 

with the International Association of Volcanology and 

Chemistry of the Earth's Interior (IAVCEI), requested 

WOVO member institutions to establish contacts with 

civil aviation authorities to improve communications 

between ground-based observatories and air traffic in 

order to minimize the volcanic hazards to aircraft. 

USA efforts In the United States, there are 

approximately 56 volcanoes with historical eruptive 

activity. Forty-four of these are located in Alaska. The 

United States Geological Survey (USGS) is the principal 

agency of the United States Government with 

responsibility for assessing volcanic hazards and 

monitoring restless volcanoes. The work of the USGS 

Volcano Hazards Program is carried out through 

volcano observatories located in Hawaii, Alaska, and 

Washington. While USGS efforts focus on ground-based 

studies, two other agencies, the National Oceanic and 

Atmospheric Administration (NOAA) and the Federal 

Aviation Administration (FAA), recently joined efforts 

to monitor and track volcanic ash clouds in the United 

States. 

In 1989 a Memorandum of Understanding on 

volcanic hazard alerts between NOAA and FAA created 

a Volcanic Hazard Alert Technical Team to respond to 

volcanic eruptions affecting air operations in the United 

States. This cooperation requires that a volcanic 

advisory forecast (SIGMET) be issued every 4 hours 

regarding the status of the volcanic cloud, with a 12-

hour forecast of ash cloud behavior. The NOAA-FAA 

memorandum is currently being revised in light of 

experiences gained during the 1989-90 Redoubt 

eruptions and will more formally link the USGS with 

NOAA-FAA efforts. 

In addition to the efforts by Federal agencies, most 

airplane and jet engine manufacturers have studied the 

problem in efforts to develop mitigation strategies. The 

manufacturer's principal trade association, the 

Aerospace Industries Association of America (AIA), 

formed a Volcanic Ash Study Committee (PC334-1) in 

1991. The recommendations of this committee will be 

presented during the Seattle Symposium. 

One of the keys to addressing the problems aircraft 

have with volcanic ash is to effectively communicate 

experiences and practical solutions to the air crews and 

airline carriers. In connection with the symposium, the 

Air Line Pilots Association (ALP A), the Air Transport 

Association (ATA), and the Flight Safety Foundation 

(FSF) have all taken active roles to communicate about 

the ash problem with their members and constituents, 

both nationally and internationally. Members of these 

organizations were involved in both the planning of the 

Seattle Symposium and earlier efforts under the 

direction of ICAO. 

We hope that all participants in the First International 

Symposium on Volcanic Ash and Aviation Safety will 

leave Seattle with a clearer understanding about the 

threat which volcanic hazards pose to aviation safety. 

REFERENCES CITED 

Brantley, S. R., (ed.), 1990, The eruption of Redoubt 

Volcano, Alaska, December 14, 1989-August 31, 

1990: U.S. Geological Survey Circular 1061, 33 pp. 

Fox, T., 1988, Global airways volcano watch is steadily 

expanding: ICAO Bulletin, April, p. 21-23. 

Smith, W. S., 1983, High-altitude conk out: Natural 

History, v. 92, no. 11, p. 26-34. 

Steenblik, J. W., 1990, Volcanic ash: a rain of terra: Air 

Line Pilot, June/July 1990, p. 9-15,56. 

ACKNOWLEDGMENTS 

Working to bring together experts from many diverse 

fields has been a unique experience in multicultural 

relations. In addition to participants from more than a 

dozen foreign countries, we had to learn to view the 

problem of aircraft encountering ash through the eyes of 

passengers and aircrews, geologists and meteorologists, 

engineers and manufacturers, airline carriers and airtraffic managers, and even attorneys. We hope that this 

multi-disciplinary dimension is apparent in the program 

for the symposium. We especially appreciate the 

cooperation of those from outside the scientific 

community for their willingness to work within the 

more traditional meeting format of scientific exchange. 

We gratefully acknowledge the skill and efforts of 

Marsha Simpkins and Deloris Klausner of the Branch of 

Igneous and Geothermal Processes (USGS/Denver) who 

assisted in preparation of this volume, and the editorial 

guidance provided by the Branch of Technical Reports 

(USGS/Denver). 

Volcanic Ash and Aviation Safety 3 
PROGRAM 

(Abstracts listed alphabetically within each topic) 

KEYNOTE and LUNCHEON TALKS 

Donald D. Engen 

(Keynote address) 

Christopher G. Newhall 

(Welcome From Organizing Committee) 

Eric Moody (British Airways) 

(Luncheon, July 9: BA Encounter with Ash Over Galunggung) 

Zygmund Przedpelski (General Electric) 

(Luncheon, July 10: AlA report) 

Dallas Peck (U.S. Geological Survey) 

(Luncheon, July 11: Mount St. Helens) 

REDOUBT ERUPTIONS 

Ernest Campbell 

747-400 Airplane Damage Survey Following a Volcanic Ash Encounter 

Charles F. Criswell 

Volcano Eruption Notification and Aircraft Aviation: Lessons from December 15, 1989 

Encounters 

Edward Haeseker 

Alaska Airlines Operating Procedures During the 1989-1990 Redoubt Eruptions 

T. P. Miller and J. N. Davies 

The 1989-90 eruption of Redoubt Volcano: Chronology, character, and effects 

Z. J. Przedpelski and T. J. Casadevall 

Impact of Volcanic Ash from Redoubt Eruption on GE CF6-80C2 Turbofan Engines 

Anders Westman 

New Roles for Airports in Response to Volcanic Disturbances 

VOLCANOES AND ASH CLOUDS 

Jorge Barquero H. 

Volcanic Eruptions and Aviation Safety in Costa Rica 

G. Bayhurst, A. Mason, and K. Wohletz 

Volcanic Ash Characterization 

4 Volcanic Ash and Aviation Safety 
James E. Beget, Samuel E. Swanson, and David Stone 

Frequency and Regional Extent of Ash Eruptions from Alaskan Volcanoes 

Sutikno Bronto 

Predicting the Times and Intensities of Explosive Volcanic Eruptions 

T. J. Casadevall and T.M. Murray 

Gases and Aerosols in Volcanic Eruptions Clouds: Impacts on Aircraft 

Peter W. Francis, S. Self, and L. S. Glaze 

Lessons From the 16 September 1986 Eruption of Lascar Volcano, North Chile 

J. S. Gilbert, S. J. Lane, and R. S. J. Sparks 

Particle Aggregation Controlled by Electrical Charge in Volcanic Plumes 

Alain Gourgaud, G. Camus, M.C. Gerbe, and P.M. Vincent 

Mitigation Methods of Volcanic Hazards During Eruptions: Galunggung Volcano 1982-83 

Grant Heiken 

Volcanic Ash: What it is and How it Forms 

Catherine J. Hickson 

Holocene Volcanism in the Canadian Cordillera 

M. Krafft, S.R. Brantley, and C.G. Newhall, 

Understanding Volcanic Hazards 

Francois LeGuern and Alain Bernard 

Volcanic Products and Aviation Safety: Modeling the Gas-particle Conversions 

I. V. Melekestsev, O.A. Braitseva, and V. Yu. Kirianov 

Volcanic Ash from Explosive Eruption in Kamchatka and Kuriles as Source of Hazard for 

Aviation 

William E. Scott and Robert G. McGimsey 

Mass, Distribution, Grain Size, and Origin of 1989-1990 Tephra-fall Deposits of Redoubt 

Volcano, Alaska 

Stephen Self and George P .L. Walker 

Ash Clouds: Conditions in the Eruption Column 

Tom Simkin 

Volcanoes: Their Occurrence and Geography 

R. S. J. Sparks, M. I. Bursik, S. N. Carey, and J. S. Gilbert 

Dispersal of Ash by Volcanic Eruption Columns 

Donald A. Swanson 

Current State of Volcano Monitoring: Strengths and Weaknesses 

Samuel E. Swanson and James E. Beget 

Thermal Properties of Volcanic Ash 

Volcanic Ash and Aviation Safety 5 
C. J. N. Wilson 

Ash Fall Deposits from Large Scale Phreatomagmatic Volcanism: Limitations of Available 

Eruption Column Models 

DAMAGE AND IMPACTS 

David M. Bailey 

Cleanup of the Grant County Airport After May 18, 1980 Eruption of Mount St. Helens 

Alain Bernard and Francois LeGuem 

The Ingestion and Melting Properties of Volcanic Ash in Aircraft Engines 

T. J. Casadevall, G.P. Meeker, and Z.J. Przedpelski 

Volcanic Ash Ingested by Jet Engines 

Rand Decker 

Multi phase Flows and the Modeling of Gas/Particle Flows 

M.G. Dunn and D.P. Wade 

Influence of Volcanic Clouds on Gas Turbine Engines 

Lee Huskey and Bradford Tuck 

Economic Consequences of the 1989-90 Mt. Redoubt Eruptions: Assessment Methodology 

and Anecdotal Empirical Evidence 

Juergen Kienle 

Volcanic Ash-Aircraft Incidents in Alaska Prior to December 15, 1989, 747-Redoubt 

Encounter 

John R. Labadie 

Mitigation of Volcanic Ash Effects on Aircraft Operating and Support Systems 

D. Pieri and R. Oeding 

Grain Impacts on an Aircraft Windscreen: The Redoubt 7 47 Encounter 

Widen Tabakoff 

Performance Deterioration on Aircraft Jet Engines with Presence of Solid Particles 

Alan Weaver 

Volcanic Ash Ingestion: A Perception of Relative Risk 

Lester M. Zinser 

Effects of Volcanic Ash on Aircraft Powerplants and Airframes 

COMMUNICATIONS AND PROCEDURES 

Ernest Campbell 

Recommended Flight Crew Procedures if Volcanic Ash is Encountered 

James E. Evans 

Development of a Real Time ATC Volcanic Ash Advisory System based on Aviation 

Information System 

6 Volcanic Ash and Aviation Safety 
Peter M. Foreman 

Warning Systems and Pilot Procedures 

Tom Fox 

Volcanic Ash-International Regulatory Aspects 

R. F. Hamley and D. H. Parkinson, 

Seattle ARTCC Response to Volcanic Eruptions of Mount St. Helens 

R. W. Johnson and T. J. Casadevall 

Coping with the Aircraft Ash-Cloud Problem in Australia 

Lindsay McClelland 

Smithsonian Global Volcanism Network: Facilitating Communication of Eruption 

Information 

Edward Miller 

Volcanic Ash and Aircraft Operations 

Bobbie Myers and George J. Theisen 

Volcanic-Event Notification at Mount St. Helens 

Saburo Onodera and Kosuke Kamo 

Aviation Safety for Ash Clouds in Japan and JAL's System for Sakurajima's Eruptions 

Rodney J. Potts and Frank Whitby 

Volcanic Ash Warnings in the Australian Region 

R.I. Tilling, T. J. Casadevall, G. Heiken, and G. E. Sigvaldason 

Volcano Observatories and Volcanic Ash Warnings 

METEOROLOGY and ASH CLOUD MODELING 

James S. Ellis and Thomas J. Sullivan 

ADPIC Calculated Volcanic Ash Cloud Transport and Fallout from 12/20/90 MSH Puff 

Norman Hassel and Edward Hudson 

Description of the Wind Profiler Installed in Homer, Alaska 

Gary L. Hufford 

New Technologies to Support Forecasting Volcanic Plume Movement 

Lee Kelley 

Forecasting Volcanic Debris in Alaska 

Herschel Knowles 

Generation and Distribution of Graphical Depictions of Volcanic Ash Plumes 

G. Macedonio, M. T. Pareschi, Papale, M. Rosi, and R. Santacroce 

A Statistical Approach in Assessment of Volcanic Hazard for Air Traffic: Appliccation to 

Vesuvius, Italy 

Volcanic Ash and Aviation Safety 7 
Anthony Mostek 

NOAA's Response to the Mt. Redoubt Eruptions of December 1989 

T. L. Murray, C. I. Bauer, and J. F. Paskievitch 

Using a Personal Computer to Obtain Predicted Plume Trajectories during Redoubt 

Eruptions 

Thomas W. Schlatter and Stanley G. Benjamin 

A Mesoscale Data Assimilation System Adapted for Trajectory Calculations over Alaska 

Arthur H. Smith 

Preparation and Dissemination of Volcanic Ash Plume Information by the National 

Meteorological Center 

Barbara J. B. Stunder 

Modeling Volcanic Ash Transport, Dispersion and Deposition 

H. L. Tanaka 

Development of a Prediction Scheme for the Volcanic Ash Fall from Mt. Redoubt 

Michael A. Tomlinson 

Current Procedures for In-flight Advisories Regarding Volcanic Eruptions 

Jerald Uecker 

The Aeronautical Volcanic Ash Problem 

P. Versteegen, C. Gallaway, and D. D'Antrachy 

Aircraft A voidance Regions from Volcanic Ash 

DETECTION and TRACKING 

I J. Barton and A. J. Prata 

Detection and Discrimination of Volcanic Ash Clouds by Infra-Red Radiometry 

II: Experimental 

Real D'Amours 

Current and Future Capabilities--Forecasting the Trajertory, Transporation and Dispersion 

of Volcanic Ash Clouds--CMC 

Kenneson G. Dean and Larry Whiting 

Analysis of Satellite Images of Redoubt Volcano Plumes 

David M. Harris 

Automated Detection, Evaluation, and Notification of Volcanic Ash Clouds--An Integrated 

System 

U. G. Hartmann, R. H. Hertel, J. 0. Maloy, and H. A. Roeder 

GEO-TOMS: Total Ozone Mapping Spectrometer for Ozone & S02 Monitoring from 

Geostationary Satellite 

8 Volcanic Ash and Aviation Safety 
Peter V. Hobbs, Lawrence F. Radke, and Derek J. Coffman 

Airborne Lidar Detection and In-Situ Measurements of Ash Emissions from the 1990 

Volcanic Eruptions of Mount Redoubt 

R. P. HobliH 

Lightning Detection and Location as a Remote Ash-Cloud Monitor at Redoubt Volcano 

Frank R. Honey 

Passive, 2 Spectral Channel Thermal Infrared Imaging Systems for Discrimination of Ash 

Clouds 

Chris Jonientz-Trisler, Bobbie Myers, and John Power 

Seismic Identification of Gas-and-Ash Explosions at Mount St. Helens: Capabilities, 

Limitations and Regional Application 

Kosuke Kamo, Kazuhiro Ishihara, and Makoto Tahira 

Prediction and Detection of Explosive Eruptions at Sakurajima Volcano, Japan 

A. Krueger, L. Walter, C. Schnetzler, S. Doiron, and G. Bluth 

Volcanic Hazard Detection with TOMS 

James S. Lynch 

Mount Redoubt: Tracking Volcanic Ash Plumes from Space 

Michael Matson 

Use of Satellites for Detecting and Tracking Volcanic Clouds 

Steven R. McNutt 

Volcanic Tremor Amplitude Correlated with Eruption Explosivity and its Potential 

Application for a Volcanic Ash Warning System 

Mark Musolf 

Airborne Radar Detection of Volcanic Ash 

Reginald Newell 

Volcanoes and Atmospheric Temperatures 

A. J. Prata, and I. J. Barton 

Detection and Discrimination of Volcanic Ash Clouds by Infra-Red Radiometry I: Theory 

W. I. Rose, and Alex Kostinski 

Radar Remote Sensing of Volcanic Clouds 

Yosihiro Sawada 

Regional Monitoring of Volcanic Ash Cloud by Geostationary Meteorological Satellite 

(GMS) 

D. J. Schneider, and W. I. Rose 

Utility of A VHRR Sensor for Remote Sensing of Alaskan Eruption Clouds 

Volcanic Ash and Aviation Safety 9 
Tumpal Situmorang, and Subroto Modjo 

The Use of Satellite Imagery in Tracking Volcanic Ash Clouds in Indonesia: A New 

Possibility for Aviation Safety 

Indroyono Soesilo 

Volcanic Ash Detection and Tracking System Applied To Indonesia 

Melvin L. Stone 

Application of Radar for the Observation of Volcanic Ash 

10 Volcanic Ash and Aviation Safety 
ABSTRACTS 

CLEANUP OF GRANT COUNTY AIRPORT 

AFTER MAY 18, 1980, ERUPTION OF MOUNT 

SAINT HELENS 

David M. Bailey, Port of Moses Lake, Moses Lake, WA 

On May 18th of 1980, Mount Saint Helens, located in 

the southwest portion of the State of Washington, 

erupted. This eruption spewed a considerable amount 

of volcanic material throughout the State which 

eventually progressed over the northern tier states. The 

amount of volcanic material that eventually was 

deposited at the Grant County Airport ranged from 3-4 

inches of fine powder ash. 

As a brief background, the Grant County Airport, 

located in central Washington, is approximately 120 

miles from Mount Saint Helens. The airport, formerly 

known as Larson Air Force Base, contains over 4,500 

An airport maintenance worker removes ash from the tail assembly of a 

Boeing 747 airplane at Moses Lake, Washington following the May 18, 1980 

eruption of Mount Saint Helens Volcano. This eruption had a major impact 

acres. Our main runway is 13,500' x 300' and our crosswind runway is 10,000' x 100'. The airport is extensively 

used as a research and development, heavy jet training 

facility by a number of air frame manufacturers and air 

carriers. We provide services to the Boeing Company, 

Japan Airlines, McDonnell Douglas, McChord Air Force 

Base, Alaska Airlines, Big Bend Community College and 

approximately 300 other foreign and domestic air 

carriers. 

During the Symposium, I would like to discuss the 

effect the ash had on the Airport and a detailed 

description as to the process that we used to remove the 

ash from both the Airport operating areas and the 

Industrial Park. I would also like to further discuss 

some of the problems we had with disposing of the 

material and the effect on aircraft and equipment. 

Basically, we had the airport back in operation within 

thirty days. 

on air operations in the Pacific Northwest and caused the temporary closing of 

several important airfields. Photograph courtesy of the Port of Moses Lake. 

Volcanic Ash and Airline Safety 11 
VOLCANOES AND AVIATION SAFETY IN 

COSTA RICA 

Jorge Barquero H., Observatorio Volcanologico y 

Sismologico de Costa Rica, Universidad Nacional, HeredU:z, 

Costa Rica 

The active volcanoes in Costa Rica are located in the 

Guanacaste Volcanic and Central Volcanic Ranges. Poas 

and Irazu volcanoes had several strombolian eruptions 

in historical times that issued large quantities of ash. 

Fine ash moved to the west and southwest of the 

volcanoes reaching different distances and altitudes due 

to the predominant trade wind directions. Therefore, 

precautions should be taken for the air traffic during 

future eruptions. 

Juan Santamaria International Airport (main Costa 

Rican airport) is located 23.2 km south from Poas 

volcano and 41.6 km southwest from Irazu volcano. 

Commercial airline routes fly over or very close to the 

volcanoes. For example, Poas volcano (8,884 feet high) is 

in the route of commercial airlines to Miami with a 

minimum flying altitude of 12,000 feet. Irazu volcano 

(11,457 feet high) is in the airline routes to Panama and 

Puerto Limon with a minimum flying altitude of 14,000 

feet. Arenal volcano (5,380 feet high) is located 73.6 km 

from the Santamaria airport. Arena} is the most active 

volcano in Costa Rica and it is in the course of 

commercial flights to Managua, Nicaragua, with a 

minimum flying altitude of 11,000 feet. Between 1963-

1965, during the last active period of Irazu volcano, large 

quantities of ash were deposited on the Santamaria 

airport, however, we do not have official records to 

explain what happened with the air traffic during times 

of heaviest ashfall. 

The cooperation between pilots, air controller and 

volcanologists is very important. From the air it is 

possible to see anomalous activity in volcanoes. For 

example, in 1962 a pilot called a newspaper to inform 

about the first columns of vapor issued by Irazu volcano 

during the 1963-65 active period. This was the 

beginning of cooperation between aviation and 

volcanology. Three years ago, Poas volcano had very 

strong gas emissions. At times private and commercial 

airline pilots reported to air controllers strong odors and 

the height of the gas columns. We do not have an 

official linkage with the civil aviation authorities, but 

concerned air controllers notified our observatory. We 

hope that by the end of this year (1991) we will have a 

working group to make this type of cooperation more 

effective. It is imperative to take into account possible 

ash and gas eruptions when planning air traffic and 

future airport sites. 

12 Volcanic Ash and Airline Safety 

DETECTION AND DISCRIMINATION OF 

VOLCANIC ASH CLOUDS BY INFRARED 

RADIOMETRY II: EXPERIMENTAL 

I. J. Barton and A.J. Prata, CSIRO, Aspendale, Australia 

To test the feasibility of using infrared radiation to 

detect and discriminate volcanic ash clouds, an absolute, 

self-calibrating, filter radiometer has been built. The 

radiometer has up to five selectable filters and two 

temperature controlled precision blackbodies for 

internal calibration. The input signal is chopped against 

that from a third reference blackbody. The radiometer 

has been flight tested up to 25,000 feet and has 

performed well. During the flight tests, measurements 

were made in both clear skies and cloudy conditions at 

varying heights and viewing angles. Results from these 

tests will be presented and compared to theoretical 

calculations. 

The radiometer has also been used to view the 

volcanic plume emanating from Mt. Sakurajima on the 

Japanese island of Kyushu. For these tests the 

radiometer was ground based and pointed up towards 

the plume. These results will be presented and 

compared with measurements of normal water /ice 

clouds. Measurements were also made at 8.6 J..Lm in an 

attempt to monitor the S02 concentration in the volcanic 

plume. Corroborative measurements of S02 were also 

made using a COSPEC instrument. 

VOLCANIC ASH CHARACTERIZATION 

G. Bayhurst, A. Mason, and K. Wohletz, Los Alamos 

National Laboratory, Los Alamos, NM 

Detailed studies of ash particles can be used to better 

understand problems associated with ash transport such 

as engine damage, visibility, sunlight blockage, and 

dispersion and deposition of ash. We are using several 

analytical techniques to characterize ash particles in 

terms of size, mineralogy, and elemental composition. 

We have developed a program to characterize 

particles using a scanning electron microscope (SEM) 

with an energy dispersive X-ray detector (EDS). Once 

we have properly prepared and mounted the ash 

samples, the SEM and its software can describe the 

particles' size, area, shape, chemical composition, and 

density. The data obtained from the SEM are then 

reduced by a computer program to obtain distribution 

graphs for size, density, shape, and mineralogy. Finally, 

we analyze the samples by traditional optical 
microscopy to verify their mineralogy and to examine 

their crystallinity. 

This method was used on the ash that damaged the 

engines from the KLM flight of December 15, 1989, 

which flew through the ash cloud from Redoubt 

Volcano. The sample studied was collected from the 

pitot-static system and had not been exposed to any 

engine parts that may have changed its characteristics. 

This sample will be used to demonstrate the capabilities 

and information obtained from our program. 

FREQUENCY AND REGIONAL EXTENT OF 

ASH ERUPTIONS FROM ALASKAN 

VOLCANOES 

James E. Beget, Samuel E. Swanson, and David Stone, 

University of Alaska, Fairbanks, AK 

Historic records indicate Alaskan eruptions large 

enough to disrupt air traffic have had an average 

recurrence interval of about 5-10 years during the last 

century. These small eruptions typically each last a few 

hours, and disperse about 0.1-0.2 km3 of ash in a plume 

several hundred kilometers long. Mt. St. Augustine and 

Mt. Redoubt have erupted most often and so constitute 

the greatest hazards to air traffic. 

The frequency and style of tephra eruptions from 

Alaska volcanoes has changed through time. Some 

prehistoric eruptions were hundreds of times larger than 

the 1989-1990 Mt. Redoubt event. The 1912 Katmai 

eruption put an estimated 25 km3 of ash into the 

atmosphere during a sustained eruption lasting almost 3 

days, while prehistoric ashfalls have reconstructed 

volumes of 50-100 km3 and produced significant fallout 

more than 1,500-2,000 km from the source volcanoes 

over areas of 1oS-1o6 km2. If a large Alaskan volcanic 

eruption occurred today it would put huge volumes of 

ash into the air and might blanket most of Alaska and 

northwest Canada or large regions of the northern 

Pacific Ocean for a week or more. 

THE INGESTION AND MELTING PROPERTIES 

OF VOLCANIC ASH IN AIRCRAFT ENGINES 

A. Bernard, Universite Libre, Brussels, Belgium and F. 

LeGuern, CEN-Saclay, Gif sur Yvette, France 

Volcanic eruptions represent a significant hazard for 

civil air transport. Numerous encounters of aircraft 

flying through volcanic plumes have been reported in 

the past 15 years. These incidents were sometimes 

serious as in December 1989 when a KLM Boeing 747 

flying through the eruptive plume of Redoubt volcano in 

Alaska suffered severe engine damage resulting in an 

emergency landing in Anchorage. 

We present here a SEM study of volcanic ash deposits 

found in engines of aircraft which flew through volcanic 

plumes. These ash deposits are characterized by a 

uniform glassy layer with a flat surface where all the 

characteristics of the original material have been 

obliterated. This glassy layer is often covered by a 

second layer formed by the accumulation of ash 

fragments slightly adhering together on a party melted 

matrix. The original crystal morphology is conserved in 

this second layer. On top of the glassy layer, abundant 

microspherules (0.1-15J..1m) with morphologies similar to 

fly-ash are observed. These microspherules show 

variable compositions of silicates and oxides. All these 

observations are consistent with pronounced melting 

and dehydration of the volcanic material in the high 

temperature regions of the aircraft engine and 

subsequent deposition on the cooler surfaces of the 

turbine vanes. This melting is the most significant 

process for volcanic hazard considerations because it 

causes the volcanic ash to adhere to engine surfaces and 

lead to the build-up of a significant deposit (several mm 

thick) which was the main cause of the engine 

shutdown. The volcanic material seems to have unique 

melting properties (low melting point, small size) since 

aircraft operations in other geographic areas with a high 

loading of dust (i.e. desert sand) are not suffering from 

this problem (W. W. Smith, 1983). 

PREDICTING THE TIMES AND INTENSITIES 

OF EXPLOSIVE VOLCANIC ERUPTIONS 

Sutikno Bronto, Volcanological Survey of Indonesia, 

Bandung,lndonesia 

Galunggung explosive volcanic eruptions in 1982 

caused two international flight accidents which occurred 

on 24 June and 13 July when the 747 Jumbo Jets passed 

above the volcano, from Kuala Lumpur, Malaysia to 

Perth, Australia. The planes were forced to make an 

emergeny landing on Jakarta. On 15 December 1989, a 

KLM 747- 400 aircraft entered a cloud of volcanic ash 

from Redoubt Volcano, Alaska. Although the aircrafts 

landed successfully, extensive repairs were required. 

In the last century, two of the largest eruptions in 

historic time occurred in Indonesia, i.e., Tambora (1815) 

and Krakatau (1883). Their ash cloud reached up to 150 

km high. In the last decade (1980 -1990), there were 100 

events of explosive volcanic eruptions in Indonesia, and 

Volcanic Ash and Airline Safety 13 
11 of them ejected ash reaching 4 - 27 km high. These 

ash clouds could affect both domestic and international 

air traffic. 

On the basis of past occurrences, a study of volcanic 

eruptions, particularly to predict the times and 

intensities of explosive volcanic eruptions, is being 

carried out in order to avoid air traffic accidents. This 

study is based on statistical data of precursors through 

crisis stage to volcanic explosions, and processes in the 

volcanoes' magma chamber. 

It is concluded if the magma is fractionated, the most 

explosive eruption occurs near the beginning of an 

eruption period, and the intensity of explosions caused 

by magma fractionation is lesser than that caused by 

magma mixing. 

747-400 AIRPLANE DAMAGE SURVEY 

FOLLOWING A VOLCANIC ASH ENCOUNTER 

Ernest E. Campbell, Boeing Commercial Airplane Group, 

Seattle, WA 

On December 15, 1989, a 747-400 airplane powered 

by CF6-80C2 engines, encountered volcanic ash at 

approximately 26,000 feet during descent for a landing 

at Anchorage, Alaska. All four engines flamed out, 

however, they were restarted and an uneventful landing 

was accomplished. 

The following survey provides a brief summary of 

the airplane damage: 

All four engines sustained extensive compressor 

erosion and hot section damage. All four engines, nose 

cowls and thrust reverses were removed and replaced. 

Fuel, oil, hydraulic and potable water system were 

contaminated. Each system was drained and cleaned. 

Pilots' windshields, cabin windows forward to door 

two, navigation and landing light covers were sand 

blasted, all removed and replaced. 

Wing, stabilizer and vertical-fin leading edges and 

leading-edge flaps were sand blasted, all were removed 

and replaced. 

All pilot and static probes were plugged, removed 

and replaced. 

Electronic equipment (black boxes) contaminated, all 

removed and replaced. 

Entire interior of airplane contaminated. All seats, 

equipment, side walls, ducts, etc., were removed and 

cleaned or replaced. 

Cost of airplane repair over 80 million dollars. 

14 Volcanic Ash and Airline Safety 

RECOMMENDED FLIGHT-CREW 

PROCEDURES IF VOLCANIC ASH IS 

ENCOUNTERED 

Ernest E. Campbell, Boeing Commercial Airplane Group, 

Seattle, WA 

GROUND OPERATION 

If airplane operations from or to airports 

contaminated with volcanic ash can not be avoided, 

accomplish the following: 

--Airplane exposed surfaces should be cleared of any 

ash which may contaminate lubricated parts, enter 

engines gas path, air-conditioning system and other 

orifices. 

--Restrict APU use to engine starts. 

--Avoid use of air conditioning packs on the ground. 

--Do not taxi with any engine shutdown. 

--Allow ash and dust to settle prior to takeoff. 

--Use rolling take-off technique. 

FLIGHT OPERATIONS 

Avoidance 

Use all possible means to avoid areas of known 

volcanic activity: 

--Review all NOTAMs and ATC directives for current 

status. 

-Plan flight to stay upwind of volcanic ash. 

WARNING: Airplane radar will not detect volcanic 

ash. 

Recognition 

The following conditions have been observed by 

flight crews: 

--Heavy static discharges. 

--Glow in engine inlets. 

-Ash appearing in the cockpit and cabin with an acid 

odor. 

--Multiple engine malfunctions and flame-outs. 

-Decrease in, or loss of airspeed. 

--False cargo fire warnings. 

Procedures 

If volcanic debris is inadvertently encountered, 

accomplish the following: 

-Immediately reduce thrust to idle. 

--Exit ash as quickly as possible. 

--Autothrottles off. 

--Engine and wing anti-ice on. 

--All A/C packs on/high. 

--Start APU (if available). 

--Oxygen mask on and 100% (if required). 

--Ignition on. 

--Monitor EGT limits. 

--Engine restart (if required). 
--Monitor airspeed and pitch attitude. 

--Land at nearest suitable airport. 

VOLCANIC ASH INGESTED BY JET ENGINES 

T. J. Casadevall, G. P. Meeker, U.S. Geological Suroey, 

Denver, CO, and Z. J. Przedpelski, General Electric Aircraft 

Engines, Evendale, OH 

Ingestion of volcanic ash by jet engines may cause 

serious deterioration of engine performance due to 

erosion of moving engine parts, such as compressor 

blades and turbine blades, and accumulation of partially 

melted ash in hot zones within the engine. Since 1980, at 

least 5 encounters between jet-powered aircraft and 

volcanic ash clouds have resulted in temporary engine 

failure. 

In this study we used petrographic thin section, 

scanning electron microscope, and electron microprobe 

techniques to analyze volcanic ash deposits from the 

December 15, 1989, eruption of Redoubt Volcano as well 

as deposits found within the engines of a Boeing 747-400 

that flew into the ash cloud created by the December 15 

eruption. 

Ash from the deposits of the December 15 eruption 

ranges in diameter from less than 1 micron to slightly 

greater than 100 microns with a mean diameter of about 

20 microns. Volcanic ash was reduced to about 7 

microns diameter by the time it entered the combustor 

section of the engine where melting occurred. Melted 

ash deposits in the hot combustor and turbine sections of 

the engine display fluidal textures that indicate flowage 

of material occurred during or after initial deposition. 

Vesicles are common in the remelted deposits. The glass 

is enriched in total Si02 as compared to the deposits 

from the ash cloud. In addition to the primary minerals 

of plagioclase, pyroxene, and Fe-Ti oxides found in 

deposits from the ash cloud, deposits from the engines 

also include metal particles derived from abrasion of 

engine parts, principally from the compressor area 

where titanium metal alloy and stainless steel are used 

extensively. Oxide particles rich in Fe, Cr, and Ni 

derived from stainless steel are found coating the 

surfaces of ash grains and are present as spheres in the 

melted ash matrix. 

The principal components of volcanic ash are 

volatile-poor glass and minerals, which are unlikely to 

melt at temperatures below 900-1,000°C. By reducing 

engine power to the minimal setting, the engine 

temperature can be reduced below the threshold at 

which volcanic ash is likely to melt. 

GASES AND AEROSOLS IN VOLCANIC 

ERUPTIONS CLOUDS: IMPACTS ON 

AIRCRAFT 

T. J. Casadevall, U.S. Geological Suroey, Denver, CO, and 

T. M. Murray, Boeing Company, Seattle, WA 

Gases and aerosols of volcanic origin are essential 

components of ash clouds produced during explosive 

eruptions. Major species include nonreactive gases 

H20, C02, CO, and H2, and reactive (corrosive) gases 

502, H2S, HC1, and HF. Concentrations of these gases 

in ash clouds depend largely on the degree of dilution 

by ambient atmosphere and in distal clouds are in the 

range of <<1 ppm to 100 ppm. Water vapor also 

condenses from the atmosphere ingested into the 

growing eruption cloud. Volcanic gases are removed 

from the ash cloud during the formation of acidic 

aerosols and through adsorption onto silicate ash 

particles. Aerosols vary in diameter from <<1 micron up 

to 10 microns. In the cold, oxidizing environment of the 

lower stratosphere, 502 is converted to sulfuric acid 

H2S04 aerosols and eventually to sulfate particles that 

may remain suspended long after the larger silicate 

particles have settled from the cloud. 

At these low concentrations and for the usually brief 

exposures of most encounters, volcanic gases and 

aerosols by themselves do not pose an immediate threat 

to human life or to aircraft integrity. 502 and H2S may 

be detected by smell to produce nausea and cause 

anxiety; however, in the concentrations found in 

volcanic clouds these gases are not toxic and do not 

threaten health. The principal problem for airplanes 

from gases and related sulfate particles is the 

deterioration of materials prompted by direct chemical 

attack or enhanced corrosion processes. These processes 

pose a potentially serious long-term threat to the 

integrity of the aircraft. The major deterioration 

processes include corrosion of metal parts and surface 

coatings in the hot sections of jet engines (sometimes 

referred to as "hot corrosion"); contamination of plastic 

insulation and neoprene hosing in air distribution 

systems; corrosion of electrical contacts in avionics; and 

pitting, crazing, and embrittlement of windows due to 

sulfuric acid attack. In addition, the dielectric properties 

of some conformal coatings covering printed circuit 

cards may change due to the presence of the volcanic 

gases. 

Volcanic Ash and Airline Safety 15 
VOLCANO ERUPTION NOTIFICATION 

AND AIRCRAFT A VOIDANCE 

Charles F. Criswell, Federal Aviation Administration, 

Anchorage, AK 

Since the first eruption of Mt. Redoubt, Alaska, in 

December 1989, the Federal Aviation Administration 

(FAA) has made every effort to keep the aviation 

community apprised of volcanic activity. While our 

initial attempts at eruption notification were not totally 

satisfactory, we have made substantial progress in that 

area to date. However, even with the progress, nothing 

in the notification and alerting process can prevent 

penetration of the ash cloud. 

Eruption notification in Alaska begins with a report 

from the Alaska Volcano Observatory or a pilot report. 

Following eruption notification by either source, the 

Anchorage Air Route Traffic Control Center (ARTCC) 

notifies all air carriers via the "CEDA" network that an 

eruption has occurred and begins preparing a Notice to 

Airman (NOTAM). The Center Weather Unit (CWU) 

develops a Significant Meteorological Information 

statement (SIGMET) and a Center Weather Advisory 

(CWA). A NOTAM, SIGMET, or CWA are aviation 

advisories that identify a change in the components of 

the National Airspace System or identifies weather 

phenomena that could affect the safety of flight. While 

these advisories are being formatted, the ARTCC notifies 

all other aviation users via an automated, multi-tasked 

fax machine that an eruption has occurred. Once the 

advisories have been formatted, they are then 

transmitted by air-to-ground radio or teletype, 

whichever is appropriate, to all users. Aircraft in flight 

are immediately issued SIGMET and NOTAM 

information as it becomes available, including all 

updates. 

Immediately after the NOT AM's, SIGMETs, and 

CWA's are formatted and transmitted, the CWU 

develops a chart depicting the flow pattern of the ash 

cloud. This instrument is developed using winds aloft 

reports and upper winds forecast. Once this chart is 

designed, it is transmitted via automated fax to all fax 

recipients. Aircraft in flight do not have access to this 

chart; therefore, in order to avoid ash, they must depend 

on controller advisories and their own visual contact 

with the ash cloud. Controllers must also depend on 

pilot observations to assist them in helping other aircraft 

avoid ash clouds. In the case involving ash damage to a 

B-747, controllers issued at least two advisories to the 

aircraft about the ash pattern, including other aircraft 

reports of the ash cloud's position before the aircraft 

entered the ash. 

16 Volcanic Ash and Airline Safety 

Not only do air traffic controllers depend on pilot 

observations to tell them where the ash cloud is, they 

also relay this vital information to other pilots to assist 

them in avoiding the cloud. Controllers cannot see ash 

clouds on radar; therefore, they are unable to provide 

course guidance to avoid them. Radar vectors are still 

issued for arrival and departure routings; however, pilot 

occurrence is solicited. Even with all the multiple 

notifications and in-flight advisories given to pilots, 

controllers still deperid on the pilot's ability to see ash 

clouds in order to avoid them. 

CURRENT AND FUTURE CAPABILITIES IN 

FORECASTING THE TRAJECTORIES, 

TRANSPORT AND DISPERSION OF 

VOLCANIC ASH CLOUDS AT THE 

CANADIAN METEOROLOGICAL CENTRE 

Real D' Amours, Canadian Meteorological Centre, Dorval 

Canada 

A 3-D Trajectory Model has been operational at the 

Canadian Meteorological Centre for several years. The 

model is executed on a request basis to estimate future 

trajectories of air parcels originating from anywhere in 

North America at any desired level. The model has been 

used extensively to support the forecasting needs of the 

Canadian Regional Weather Centres during volcanic 

eruptions. The model executes very quickly on CMC's 

Cray-XMP and results are transmitted within a few 

minutes both in chart and message form. A description 

of the model will be given along with examples of 

applications to the eruptions of Mount Redoubt in early 

1990. 

A large-scale transport/ dispersion/deposition model 

(CANERM) is also operational at CMC. Although it has 

been primarily designed for tracking the radioactive 

cloud resulting from a large nuclear accident, CANERM 

can be used to estimate the evolution of the ash plume 

from a large volcanic eruption. Given a reasonable 

description of the source characteristics, concentration 

estimates of airborne ash particles can be obtained. A 

brief description of the model will be given, along with 

its current capabilities and limitations. Example of 

results will be shown and future prospects will be 

discussed. 
ANALYSIS OF SATELLITE IMAGES OF 

REDOUBT VOLCANO PLUMES 

Kenneson G. Dean and Larry Whiting, University of 

Alaska, Fairbanks, AK 

The discharge of ash and the resulting danger to air 

transportation was one of the primary hazards 

associated with the 1989-1990 eruption of Redoubt 

Volcano. Satellite images are a valuable source of 

information for the analysis of the plume, especially if 

the data is available in a timely manner. Advanced Very 

High Resolution Radiometry (A VHRR) images were 

acquired and analyzed, and the results provided to the 

Alaska Volcano Observatory (AVO). AVO used this 

information to access the plume and ash trajectory and 

distribution. During the first few weeks of the eruption, 

six hours elapsed after a satellite pass before images 

were provided to the AVO. However, six hours was 

considered unacceptable due to the dynamics of volcanic 

processes. Thus, a procedure was developed to provide 

satellite images within 1.0 to 1.5 hours after a satellite 

pass. 

Since the start of the eruption, approximately 50 

AVHRR and Landsat digital data tapes have been 

collected for retrospective studies. A VHRR images 

recorded in late December reveal plumes that emanate 

from Redoubt and trail off to the east across Cook Inlet 

and over Prince William Sound and the Gulf of Alaska. 

Images recorded after December show plumes that were 

circular with a diameter of a few tens of kilometers. The 

plumes, as recorded by the satellites, were cold (-20 to6QOC) because they cool and expand upon rising, and 

come to equilibrium with the surrounding atmosphere. 

By relating the plume temperature recorded on the 

images to the temperature/ altitude structure of the 

atmosphere as measured by soundings, the altitude of 

the plumes were accessed. An atlas of the satellite 

images is being compiled. 

MULTIPHASE FLOWS AND THE MODELING 

OF GAS/PARTICLE FLOWS 

Rand Decker, University of Utah, Salt Lake City, UT 

There are two categories of multiphase flow theories 

that are commonly specialized for modeling dilute 

gas/particle flows; the "two-fluid" model and particle 

tracking schemes. The resulting models have been used 

to simulate the transport of particulate through straight 

and curved gas ducting, and turbine rotor cascades. In 

this paper the elements of multiphase flow mechanics 

are reviewed and those efforts, to date to apply these 

theories to gas/particle flows in air breathing propulsion 

and airfoil environments is presented. These multiphase 

flow models may have some potential in providing 

analysis of possible response scenarios to engine and/ or 

airfoil performance degradation or loss during aircraft 

operations in particle-laden flows. 

INFLUENCE OF VOLCANIC CLOUDS ON GAS 

TURBINE ENGINES 

Michael G. Dunn, CALSP AN Corporation, Buffalo, NY, 

and Douglas P. Wade, Defense Nuclear Agency, 

Alexandria, VA 

For many years, a technology program has been 

ongoing at CALSPAN in the area of gas turbine 

propulsion research that utilizes a unique facility and a 

unique experimental technique which allows one to 

subject operating gas turbine engines to an adverse 

environment like that associated with a volcanic ash 

cloud without endangering either an airplane or a flight 

crew. The response of several different engines, among 

them the Pratt/Whitney JT3D turbofan and the 

Pratt/Whitney }57 turbojet, to typical volcanic ash 

clouds has been determined during this technology 

program. 

The behavior of the individual components that make 

up a volcanic cloud are separately studied using an 

Allison TS6 combustor can, a row of T56 high-pressure 

turbine inlet nozzle guide vanes, a dust injection system 

and an external air compression source. Data obtained 

using this device provide guidance for the full-scale 

engine measurements. 

The damage modes that an engine will experience 

depends upon the particular engine, the thrust setting at 

which the engine is operating when it encounters the 

dust cloud, the constituents of the cloud, and the 

respective melting temperature of these various 

constituents. In addition, the rate at which events will 

occur depends upon the particle density (or 

concentration) of the cloud. 

An important part of the CALSP AN effort has been 

to identify which engine parameters can be read by the 

flight crew to provide an early warning of impending 

engine problems. Having determined that one has a 

problem, it is then important to learn how to operate the 

engine after it has sustained considerable damage. 

Volcanic Ash and Airline Safety 17 
ADPIC CALCULATED VOLCANIC ASH 

CLOUD TRANSPORT AND FALLOUT FROM 

THE 20 DECEMBER 1990 MOUNT SAINT 

HELENS PUFF 

James S. Ellis and Thomas J. Sullivan, Lawrence Livermore 

National Laboratory, Livermore, CA 

The 20 December 1990 Mount Saint Helens volcanic 

ash puff is used to demonstrate the regional capability of 

the ADPIC (Atmospheric Diffusion Particle-in-Cell) code 

for characterizing the ash cloud, its transport, and the 

fallout pattern at the ground. The sensitivity of the 

cloud transport to the uncertainty in the atmospheric 

winds, particle size distribution, and density are 

demonstrated. Results are presented as isopleths of 

atmospheric concentration at various altitudes and as 

ground deposition amount. A unit source amount of 

ash material is used in the calculation. 

The ADPIC code and associated wind field model, 

MATHEW, facilitate the calculation and visualization of 

the three-dimensional structure of dispersing ash clouds, 

particularly as influenced by surrounding complex 

topography. Such a calculation capability, operating in 

real-time, could be of assistance to FAA centers and 

airport facilities faced with managing air traffic in 

volcanic-hazard regions. 

Work performed under the auspices of the U. S. 

Department of Energy by the Lawrence Livermore 

National Laboratory under contract No. W-7405-Eng-48 

DEVELOPMENT OF A REAL TIME ATC 

VOLCANIC ASH ADVISORY SYSTEM BASED 

ON THE AVIATION WEATHER 

INFORMATION SYSTEM 

James E. Evans, M.I. T. Lincoln Laboratory, Lexington,MA 

The overall Air Traffic Control decision-making and 

communications system for volcanic-ash surveillance 

should be based on treating volcanic ash as a type of 

aviation weather hazard from the viewpoint of 

information dissemination. Maximum advantage 

should be taken of the aviation weather product 

generation and dissemination system currently under 

development by the FAA and the National Weather 

Service. This system will provide improved access to all 

NWS and FAA sensors for hazard determination and 

prediction, and the use of a local (i.e., weather forecast 

office domain) numerical model to create an aviation 

18 Volcanic Ash and Airline Safety 

gridded forecast which can be manipulated by the FAA 

Aviation Weather Products Generator (AWPG) to 

provide real time hazard warning displays for enroute 

and terminal controllers. 

Detection and tracing of the ash clouds can be 

facilitated by use of the data acquisition syst~ms 

associated with this initiative. In particular, we consider 

the use of ash-concentration data, as measured by 

sensors on air carrier planes and communicated via the 

ACARS (ARINC Communications Addressing and 

Reporting System) downlink, and the use of the WSR880 Doppler weather radar mosaic maps, resident in the 

A WPG, to validate numerical model predictions. 

Systems issues associated with the incorporation of data 

from specialized ash sensors and non FAA/NWS 

systems are addressed. 

This work was supported by the Federal Aviation 

Administration. The Federal Government assumes no 

liability for its contents or use thereof. 

WARNING SYSTEMS AND PILOT ACTIONS 

Peter M. Foreman, International Federation of Ai~ Line 

Pilots Associations, Canada 

When aircraft and volcanic emissions share the same 

airspace, safety depends upon arranging the aircra~t 

flight paths so that they do not encounter the volca~Ic 

products. Pilots are not always able to observe ash In 

the air. Therefore, they need the assistance of an 

external detection and warning system. Pilots will be 

the last link in the chain of communications and decision 

making. Pilots have to act, to ensure t~: safety. of the 

aircraft. There are limitations on the ability of pilots to 

respond to warnings. These limitatio~s need to ~ 

recognized and addressed by the warning. system~ If 

pilots are to successfully avoid the volcanic mater~al. 

Pilots are participating in the design of the warning 

systems to be sure that the operational result is reliable 

avoidance. Crews can assist the warning system by 

timely and precise reporting of any observations of 

volcanic material or events. 

Nothing that comes out of volcanoes .does aircra~t 

any good. Should an aircraft blunder Into volcamc 

material, the results can range from early windshield 

replacement, following encounters ~ith jus~ ~ few ash 

particles, to rapid destruction of the atrcraft, If It were to 

fly into an eruptive column. In between .those two 

extremes is a spectrum from escalating early 

maintenance costs, to complete engine flame out and 

failure of many aircraft systems, in an environment of 
blinding, choking dust and toxic fumes. The lowest 

order of problems are merely an economic concern. 

Those of a higher order are a threat to air safety. There 

are certain actions which will minimize damage and 

regain control of the aircraft flight path. It is important 

to make all crews aware of the appropriate sequences of 

actions for the aircraft types which they operate. 

VOLCANIC ASH--INTERNATIONAL 

REGULATORY ASPECTS 

Tom Fox, International Civil Aviation Organization (ICAO), 

Montreal, Quebec 

Following the incidents in Indonesian airspace in 

June/July 1982 when two jet transport aircraft suffered 

engine flame-out on all four engines due to ingestion of 

volcanic ash from the Mt. Galunggung eruption, ICAO 

has moved swiftly to amend its regulatory documents to 

include requirements to provide volcanic ash warnings 

to aircraft. The warnings are issued using existing 

aviation message formats such as the NOT AM (Notice to 

Airmen) and the SIGMET (information on 

meteorological phenomena hazardous to aviation). 

In order to support the warnings system, ICAO 

sought help from States and international organizations 

to form an international airways volcano watch. The 

idea was to base the watch on an observing triad 

comprising aircraft reports, reports from ground-based 

observing stations, and monitoring by satellite. In 

organizing the watch, advantage was taken of existing 

observing-reporting networks and procedures. In this 

regard, the success of the watch is largely due to the 

enthusiastic support of the International Air Transport 

Association (IA T A) and International Federation of Air 

Line Pilots' Associations (IFALPA) in providing special 

air reports of volcanic activity; the World Meteorological 

Organization (WMO) in arranging the provisions of 

observations of volcanic activity from all the many 

international ground-based observing networks which it 

co-ordinates and coordinating the use of meteorological 

satellites and techniques for forecasting volcanic-ash 

trajectories; and from the World Organization of 

Volcano Observatories (WOVO) in arranging for 

critically important observations from volcano 

observatories strategically sited near active volcanoes. 

Current work is concentrated on consolidating and 

extending the airways volcano watch and improving the 

warning system based on operational experience gained 

during volcanic eruptions near routes inS. E. Asia and 

inN. America. 

LESSONS FROM THE 16 SEPTEMBER 1986 

ERUPTION OF LASCAR VOLCANO, NORTH 

CHILE 

P. W. Francis, S. Self, University of Hawaii, Honolulu, HI 

and L. S. Glaze, Jet Propulsion Laboratory, Pasadena, CA 

Lascar is a 5641 m high volcano on the crest of the 

Andean chain in northern Chile. Its brief eruption in 

September 1986 illustrates some aspects of importance to 

the aviation community. The eruption took place at 

10.39 UT ( 2 min) on September 16, and lasted less than 

five minutes. A vulcanian eruption column rose to a 

height of about 15 . km, and was rapidly borne 

downwind. Ground observations and geostationary 

satellite (GOES) images showed that the eruption plume 

formed a discrete extended slug about 2 km thick at 

elevations between about 10 and 14 km, which passed 

overhead the major city of Salta, Argentina, 285 km 

distant from Lascar, less than 2 hr after the eruption. 

Ash fell at Salta, but no aircraft incidents are known, 

although the city has a major airport. By 14.12 UT the 

plume had diffused, having travelled 400 km in 3.5 hr 

and covered an area greater than 100,000 square km. 

Ash collected in Salta was 200 microns in diameter and 

consisted mostly of finely fragmented lava particles; in 

contrast to the glassy pumiceous material involved in 

recent aircraft incidents. 

From an aviation safety stand-point, the Lascar 

eruption is significant because: 

(1) it took place at an obscure volcano, not generally 

regarded as hazardous. The eruption went unnoticed in 

Chile, and might not have been recorded at all if ash had 

not fallen on Salta. 

(2) it was extremely brief, but discharged an ash 

plume which was potentially hazardous over a wide 

area. 

(3) the ash cloud travelled remarkably rapidly from 

its remote source volcano into populated areas and air 

corridors. 

There are many Lascar-like volcanoes in the world 

capable of unpredictable ash eruptions that may 

abruptly place downwind air routes at risk. While 

satellite monitoring and response techniques are clearly 

desirable, the short time scales involved emphasize the 

desirability of developing autonomous aircraft-borne 

sensor systems. Detectors sensitive to acid aerosols or 

particles in the engine airflow giving warning that the 

fringes of a plume have been entered, and enabling 

immediate response, may be more realistic than 

modified weather radars. 

Volcanic Ash and Airline Safety 19 
PARTICLE AGGREGATION CONTROLLED BY 

ELECTRICAL CHARGE IN VOLCANIC 

PLUMES 

J. S. Gilbert, S. J. Lane, R. S. J. Sparks, Bristol University, 

U.K., 

Observations at Sakurajima volcano in Japan reveal 

that during nearly continuous daily eruptions, which 

generate large volumes of ash, particles fall from 

eruption columns (at distances 2.5 - 5 km from the vent) 

as loosely bound aggregates <3mm in diameter, particles 

>200 J.Lm in diameter coated with fine ash, or as 

accretionary lapilli. Field experiments yield absolute 

charge to mass (q/m) ratios, for particles 1-250f:m in 

diameter, which range from +3 to + 6 x to-4 Ckg- and -

2 to -Sx 10-4 Ckg-1. The average q/m ratio ranges from 

+ 2 to +5 x to-5 Ckg-1. Surface charge densities 

calculated from the field data are similar to those carried 

by streams of insulating particles in laboratory and 

industrial situations. Thus, the ash particles generated 

during explosive volcanic activity at Sakurajima are 

nearly saturated with charge. These surface charges 

provide attractive forces sufficiently large to cause 

aggregation of smaller particles and the adhesion of dust 

to larger particles. Particle aggregation during fallout 

may explain the polymodal grain-size distributions 

commonly found in ash-fall deposits, and the proximal 

distribution of fine ash, as well as the distal deposition of 

coarse particles in these deposits. Our data suggest that 

electrostatic effects greatly influence the dispersal and 

deposition of ash during explosive volcanic eruptions. 

MITIGATION METHODS OF VOLCANIC 

HAZARDS DURING ERUPTIONS: CASE OF 

THE 1982-83 CRISIS AT GALUNGGUNG 

VOLCANO (INDONESIA) 

A. Gourgaud, G. Camus, M. C. Gerbe, and 

P. M. Vincent, University Blaise Pascal, Clermont-Fd, 

France 

The Galunggung volcano is located in West Java. 

Recorded historic activities (1822, 1894, 1918, 1982) were 

confined in an avalanche caldera. In 1982, three main 

eruptive styles occurred, generating (1) ash-and-scoria 

flows, (2) phreatomagmatic surges and ash falls, and (3) 

strombolian ashes and scoriae. 

During the phreatomagmatic phase, the explosivity 

increased considerably, while paradoxically the magma 

composition had evolved from andesite to primitive 

basalt. A wide maar crater was excavated. On June 24th 

20 Volcanic Ash and Airline Safety 

and July 13th, 1982, two Boeing 747 aircrafts experienced 

engine power loss due to volcanic ash during flights in 

the Galunggung area. The evolution in explosivity is 

explained by an increasing ground water/magma ratio 

during the eruption, from magmatic phase 1 to 

hydromagmatic phase 2. 

Morphoscopic analyses and frequency of the xenolitic 

and juvenile grains have been made for the entire 

sequence of 1982-83 pyroclastic deposits. Preliminary 

results show clearly that the progressive increase of the 

xenolith/juvenile magma ratio, before the end of 

magmatic phase 1, announces the phreatomagmatic 

activity (and increasing explosivity). In the same way, 

the decrease of this ratio at the end of phreatomagmatic 

phase 2, announces the strombolian phase 3 (and 

decreasing explosivity). 

Such a method may be used easily on ash fall 

deposits during the course of eruption, to anticipate the 

volcanic hazards. 

ALASKA AIRLINES OPERATING 

PROCEDURES DURING THE 1989-1990 

REDOUBT ERUPTIONS 

Edward Haeseker, Alaska Airlines, Seattle, WA 

The eruption of Mt. Redoubt, 1989-90, and the 

subsequent incident with a B747 encountering the initial 

ash cloud, sent a shock wave through the aviation 

community. A B747 ingesting sufficient quantities of 

ash to cause all four engines to stop operating in flight 

forced the airlines serving Anchorage to react by 

suspending operations. Alaska Airlines was among that 

group. 

Anchorage is too important to Alaska Airlines to just 

wait for an "All Clear" Signal before resuming service, so 

we needed a plan of action. 

Chief Pilot, Tom Cufley, was to fly on the first 

airplane from Seattle that would try a landing at 

Anchorage. On December 16 after the eruption, one of 

the normally scheduled cargo planes landed at 

Anchorage International Airport. There was a break in 

the cloud cover that would allow the flight to descend 

while maintaining visual contact with the ground. This 

was to be the foundation of our plan to resume full 

service. The idea is if ash was not visible in these cloud 

openings, then there is no danger of encountering ash 

while descending. I followed on the next flight. 

By focusing on where the ash had not fallen, Alaska 

Airlines was able to resume a full schedule. With the aid 

of wind direction and velocity information from our 

arriving airplanes, we were able to accurately determine 
ash trajectories. On-site coordination allowed for a 

realistic flight-crew briefing and debriefing. These 

combined factors made the operation a success. 

Once our flights started to arrive and depart, the 

demand for tickets increased due to other carriers 

cancelling flights. Approximately 1,800 Holiday 

passengers were stranded in Anchorage wanting to fly 

south while nearly 600 passengers were in Seattle trying 

to go north. Alaska Airlines had an obligation to fulfill 

by making sure everyone made it home for the 

Christmas Holidays. 

In addition to the 18 scheduled flights, 26 passenger 

and 20 cargo flights were added during this period. This 

caused a strain on our schedule for assigning crews to 

cover the extra flights, and it took a Herculean effort to 

free up airplanes from our regular schedule. The extra 

trips were scheduled mostly during the night and early 

morning hours when the schedule is lightest. 

The operation was also based on the "On Site Go 

Team." The team was able to evaluate the situation, 

make decisions from the scene, and be able to interpret 

the FAA Notices to Airmen (NOTAMS) as they related 

to the real conditions. The "On Site" concept allows 

decisions to be made in "Real Time". Remote operations 

rely on ash and weather forecasts and FAA NOTAMS. 

Too often, NOT AMS are broadly scoped and cover too 

wide an area, and, as we witnessed, can be misleading 

for an operation such as ours at Alaska Airlines. 

SEATTLE AIR ROUTE TRAFFIC CONTROL 

CENTER (ARTCC) RESPONSE TO ERUPTIONS 

OF MOUNT SAINT HELENS 

RF. Hamley and D.H. Parkinson, FAA ARTCC, 

Auburn, WA 

Following notification of an eruption of Mount Saint 

Helens, the Center Weather Service and Traffic 

Management Units begin a mutual effort to determine 

the extent of volcanic emissions. Ash-cloud reports are 

gathered from ground and airborne observers and ashplume movement is determined using available wind 

data. Short-term advisories and projections of volcanic 

emissions are produced within format and time 

constraints usable to air traffic operations. 

Existing data sources are extremely limited. Radar 

and satellite imagery within the ARTCC have provided 

little data on volcanic emissions during recent eruptions. 

Visual ash-cloud reports have constituted the primary 

information on the presence of ash but are not available 

after dark. Their credibility is a problem. 

Considerable upper wind data and wind forecast 

guidance is available but must be used with caution. 

Currency of upper wind observations, accuracy of 

numerical models and the possibility of recent or 

pending direction changes are vital considerations. 

Aircraft wind reports provide an essential supplement 

and verification. 

Based on the observed and predicted extent of 

volcanic emissions, the Traffic Management Unit 

examines the impact of the event upon air traffic routes. 

Advisories are sent to air traffic facilities and to system 

users, identifying affected areas and suggesting alternate 

routes. 

AUTOMATED DETECTION OF VOLCANIC 

ASH CLOUDS, EVALUATION OF HAZARDS 

TO AVIATION, AND GLOBAL 

NOTIFICATION: AN INTEGRATED SYSTEM 

David M. Harris, Salem, OR 

An automated real-time system for detecting ash 

clouds, forecasting their positions, evaluating their 

hazards to aviation, and global notification is feasible. 

The system requirements include (1) ash-cloud sensors; 

(2) an instrumental method for estimating eruption rates 

and ash-cloud source parameters; (3) a global 

communications system; (4) a real-time ash-cloud 

forecasting system; (S) a hazards evaluation scheme; and 

(6) an automated system of notification. The system 

requirements can be satisfied in the following ways: (1) 

ash eruptions can be detected instrumentally using 

ground based electric field sensors; (2) eruption rates, 

amounts erupted, and duration can be estimated from 

the amplitude and duration of harmonic tremor; ashcloud source parameters can be calculated from these 

data by using moist-atmosphere plume rise theory; (3) 

commercial satellites provide communications; (4) realtime ash-cloud forecasts are feasible using existing 

software for PCs; (5) forecast conditions can be 

evaluated using quantitative criteria and reviewed by an 

expert; (6) automated notification can be provided 

through an interface to existing civil aviation and 

hazards information systems. This paper reviews the 

system performance requirements, technical solutions, a 

possible system configuration, and estimated cost to 

develop and implement a demonstration system. 

Volcanic Ash and Airline Safety 21 
GEO-TOMS: TOTAL OZONE MAPPING 

SPECTROMETER FOR OZONE AND SULPHUR 

DIOXIDE MONITORING FROM A 

GEOSTATIONARY SATELLITE 

Ulli G. Hartmann, Robert H. Hertel, J. Owen Maloy, and 

Herbert A. Roeder, Perkin-Elmer Corporation, Pomona, CA 

GEO-TOMS (Total Ozone Mapping Spectrometer) is 

a proposed ozone and sulphur-dioxide mapping 

spectrometer designed to fly on a geostationary 

platform. It is an adaptation of the Nimbus-7 TOMS but 

is capable of imaging the whole earth disk on a CCD 

detector array. The instrument will provide 12.3 km 

spatial resolution and will provide a complete 6-

wavelength image set every 10 minutes. Based on the 

performance of the Nimbus TOMS, GEO-TOMS will be 

capable of detecting volcano eruptions and plumes and 

monitoring their progress in real time. 

A conceptual design study has identified a feasible 

desi~ approach with modest weight and power 

requtrements. The design images depolarized light from 

a 2~degree field of view onto a grating. Light from the 

grating passes through a single exit slit onto a 1024 x 

1024 CCD with an optical system that corrects the 

monochromator aberrations. Wavelength scanning uses 

a reliable cam mechanism, and a simple shutter provides 

optical zeroing. 

DESCRIPTION OF THE WIND PROFILES 

INSTALL ED IN HOMER, ALASKA 

Norman Hassel and Edward Hudson, Unisys Defense 

Systems, Inc., Great Neck, NY 

As a part of the overall system to detect and predict 

the moti?n of volcanic ash clouds, plans are being made 

to establish a small network of Wind Profilers in Alaska. 

One Wind Profiler operating at 404.37 MHz has been in 

operation in Homer, Alaska, since December 1990. The 

remainder of the network will be installed when a new 

frequency allocation is approved that will prevent 

potential interference with the 406.05 MHz band used by 

Search and Rescue Satellites (SARSA T). 

The Wind Profiler in Alaska is almost identical to the 

ones being installed in the NOAA Wind Profiler 

Demonstration Network in the midwestern United 

States. It consists of an equipment shelter and an 

antenna array. The shelter houses all the active 

comP?nents: transmitter, receiver, beam steering unit, 

and stgnal and data processors. Adjacent to the shelter 

22 Volcanic Ash and Airline Safety 

is the antenna, which is a coaxial-collinear phased array 

measuring 13 meters on a side. 

The standard NOAA Wind Profiler which was 

installed in Alaska required modifications in order to 

provide accurate data on the speed and direction of the 

upper winds in the presence of spurious reflections from 

glacial mountains and nearby sea clutter. These changes 

were accomplished by additional perimeter clutter 

fences and new computer processing algorithms to 

remove the effects of wave motion returns from the 

clear-air atmospheric echoes. 

VOLCANIC ASH: WHAT IT IS AND HOW IT 

FORMS 

Grant Heiken, Los Alamos National lAboratory, 

Los Alamos, NM 

There are four basic eruption processes that produce 

volcanic ash: (1) decompression of rising magma, gas 

bubble growth, and fragmentation of the foamy magma 

in the volcanic vent (magmatic), (2) ·explosive mixing of 

magma with ground or surface water (hydrovolamic), (3) 

fragmentation of country rock during rapid expansion of 

steam and/or hot water (phreatic), and (4) abrasion 

during collision of ash grains. Variations in eruption 

style and the characteristics of volcanic ashes produced 

during explosive eruptions depend on many factors, 

including magmatic temperature, gas content, viscosity 

and crystal content of the magma before eruption, the 

ratio of magma to ground or surface water, and physical 

properties of the rock enclosing the vent. 

Volcanic ash is composed of rock and mineral 

fragments, and glass shards. Glass shard shapes and 

sizes depend upon size and shape of gas bubbles present 

within the magma immediately before eruption and the 

processes responsible for fragmentation of that magma. 

Shards range from slightly curved, thin glass plates, 

which were broken from large, thin-walled bubble walls, 

to hollow needles broken from pumiceous melts 

containing gas bubbles stretched into thin tubes by 

magma flow within the volcanic vent. Pumice 

fragments make up the coarser-grained portions of the 

glass fraction. Particle sizes range from meters for large 

blocks expelled near the volcanic vent to nanometers for 

fine ash and aerosol droplets within well-dispersed 

eruption plumes. 

Most of the ejecta from volcanic eruptions fall out 

within a few tens of km of the source. Of major concern 

to aviation are widespread eruption plumes, which are 

dispersed downwind at elevations of 8 to 20 km and can 

drift for thousands of km. These plumes, which overlap 
Volcanic ash from the March-April 1986 eruption of Saint Augustine 

Volcano, Alaska. Scanning electron micrographs show ash rollected in 

Anchorage, 180 ml1es northeast of the volcano. The ash is composed mostly of 

dacitic glass shards and rare mineral fragments. The large clast in (a) is 

pumice coated with fine-grained glass shards. Photographs (b) and (c) show 

details of glass shards coating the pumice fragment in (a). Photograph 

courtesy of Grant Heiken. 

operational levels for air traffic, consist of very finegrained ash (mostly glass shards of <0.0001 mrn) and 

even smaller acid droplets. Very few plume densities 

have been determined in situ, but average densities for a 

plume from the 1986 eruption of Augustine Volcano, 

Alaska, observed 90 km downwind, were 63-125 x w-3 g 

m3 (with an average grain size of 1 J.lm, this is equivalent 

to 4.8-9.6 x 1013 particles/m3) 

HOLOCENE VOLCANISM IN THE CANADIAN 

CORDILLERA 

C. J. Hickson, Geological Survey of Canada, 

Vancouver, BC, Canada 

British Columbia (BC), Canada and the Yukon are 

geologically dynamic regions, encompassing subduction 

zones, rifting, and thermal anomalies (hot spots?). Some 

100 volcanic vents are arranged in five broad belts and 

all have had Holocene eruptions. Volcanoes range from 

monogenetic mafic cinder cones, to peralkaline shield 

volcanoes and calc-alkaline strato-volcanoes. The most 

recent documented eruption occurred about 200 years 

ago in northwestern BC. The most recent large 

explosive eruption occurred ca. 1.2 ka ago when a vent 

near the Alaska-Yukon border expelled ca. 30 km3 of 

pyroclastic material, covering 300,000 km2 of Yukon 

under a blanket of ash. In southwestern BC, a plinian 

eruption from Mount Meager strato-volcano, occurred 

ca. 2.4 ka ago. This eruption spread ash across southern 

BC into Alberta. The tectonic forces that produced these 

volcanoes are still active today, thus it must be assumed 

that potential for a volcanic eruption in Canada still 

exists. 

In the short term, perhaps the greatest impact on 

Canadian aviation may be from eruptions elsewhere in 

western North America. During the recent eruption of 

Mount Redoubt, Alaska, tephra drifted into Canada on 

at least two occasions and within 24 hours of the May 18, 

1980, eruption of Mt. St. Helens, enough tephra fell in 

southern BC, Alberta and Saskatchewan to cause 

concern among residents and the aviation community. 

Two previous eruptions of Mount St. Helens left thin ash 

layers in southern BC and the eruption of Mount 

Mazama left a blanket of ash several centimetres in 

thickness over southern BC and much of Alberta. An 

eruption of Mount Baker, close to one of Canada's 

busiest air routes into Vancouver International Airport, 

might have serious repercussions. Response procedures 

Volcanic Ash and Airline Safety 23 
are being coordinated between the United States and 

Canada to ensure safety and minimize disruption 

among residents and aviators. 

AIRBORNE LIDAR DETECTION AND IN SITU 

MEASUREMENTS OF ASH EMISSIONS FROM 

THE 1990 VOLCANIC ERUPTIONS OF MOUNT 

REDOUBT 

Peter V. Hobbs, Lawrence F. Radke and Derek J. 

Coffman, University of Washington, Seattle, WA 

In January and June 1990 we obtained airborne in situ 

and remote sensing lidar measurements of volcanic 

emissions from Mt. Redoubt, Alaska. The lidar 

provided excellent real-time information on the 

distribution of the volcanic effluents. The in situ 

measurements provided information on the size 

distributions, mass concentrations, and nature of the 

particles, as well as the concentrations of various trace 

gases, in the volcanic emissions. 

In post analysis, the lidar observations were 

combined with the in situ measurements to derive the 

fluxes of particles and gases from the volcano. For the 

intraeruptive emissions, the derived fluxes were: water 

vapor, -160-9440 kg s-1; C02, -30-1710 kg s-1; so2, -1-

140 kg s-1; P.articles (<48 m diameter), -1-6 kg s-1; so4, 

<0.1-2 kg s-1; HC1, <0.01-2 kg s-1; and NOx, <0.1-2 kg 

s-1. During a paroxysmal eruption of Mt. Redoubt on 

January 8, 1990, the particle (<48 J..Lm diameter)-emission 

flux averaged -104 kg s-1. 

The particle-size distributions for both paroxysmal 

and intraeruptive emissions showed nucleation (<0.1 J..Lm 

diameter) and accumulation (-0.1-1.0 Jlm diameter) 

modes. On January 8, 1990, the number of 

concentrations of particles were initially mostly in the 

accumulation and coarse particle (> 1.0 J..Lm diameter) 

modes; there were comparatively few nucleation-mode 

particles. After seven hours of aging, the concentrations 

of particles of all sizes had decreased, but nucleationmode particles were relatively more prominent. Most of 

the particle mass in the January 8 eruption was in giantsized particles, predominantly diameters of -10 J..Lm and 

-30 J..Lm. Most of the particle mass in the intraeruptive 

emissions was in the accumulation mode, with 

diameters of -0.8 J..Lm. The particles in the intraeruptive 

emissions consisted primarily of mineral elements 

without any sulfuric acid coating. Very little of the so2 

(-0.1 %) was oxidized to sulfate in the cold, dark 

conditions of the arctic atmosphere. 

24 Volcanic Ash and Airline Safety 

LIGHTNING DETECTION AND LOCATION AS 

A REMOTE ASH-CLOUD MONITOR AT 

REDOUBT VOLCANO, ALASKA 

R. P. Hoblitt, U.S. Geological Survey, Vancouver, WA 

Few of Redoubt volcano's recent eruptions were 

observed directly because of bad weather and brief 

winter days. The unseen ash clouds were a substantial 

hazard to aircraft. In the absence of direct observation, 

the presence of ash clouds was deduced, with some 

uncertainty, from seismicity. Lightning, normally rare 

around Cook Inlet, accon1panied nearly all of Redoubt's 

ash-producing eruptions. Lightning radiates broadband 

radio waves that allow remote detection and location of 

lightning and, therefore, ash clouds. As an experiment, 

the Alaska Volcano Observatory deployed a 

commercially available lightning detection system (LDS) 

around Cook Inlet. This LDS is normally used by the 

Bureau of Land Management's Alaska Fire Service to 

detect and locate cloud-to-ground lightning in Alaska's 

interior during summer months. The Cook Inlet LDS 

became operational on February 14, 1990. Lightning was 

detected in 11 and located in 9 of the 12 subsequent 

eruptions. Most cloud-to-ground lightning strikes 

occurred at or near the volcano. The number of cloudto-ground discharges produced by a given eruption was 

directly related to the quantity of ash produced. 

Discharges that occurred early in an eruption had a 

negative polarity, while late discharges tended to be 

positive; this phenomenon suggests that coarse particles 

carried a negative charge and fine particles carried a 

positive charge. Intracloud lightning, as determined 

from eyewitness accounts but not detected by the LDS, 

was more abundant than cloud-to-ground lightning and 

tended to persist in the ash clouds even at substantial 

distances from the volcano. In the February 15, 1990 

eruption, intracloud discharges persisted to a distance of 

at least 120 km from the volcano. A system capable of 

locating intracloud lightning could potentially track ash 

clouds as long as discharges persist. Lightning data 

dispel the ambiguity inherent in using seismic data 

alone, for the coincidence of seismic lightning signals 

provides compelling evidence of an ash cloud. 

Lightning detection also provides a rapid remote 

measure of eruption magnitude. Alaska Volcano 

Observatory has now acquired and deployed a cloud-toground LDS dedicated to monitoring Cook Inlet 

volcanoes. 
PASSIVE, TWO SPECTRAL CHANNEL 

THERMAL INFRARED IMAGING SYSTEMS 

FOR DISCRIMINATION OF VOLCANIC ASH 

CLOUDS 

Frank R. Honey, SpecTerra Systems Pty. Ltd., Perth, 

Western Australia 

NOAA A VHRR image data recorded and displayed 

in Perth on the 25th June 1982 by a joint CSIRO and 

Curtin University team dramatically demonstrated the 

capability for observation of the position and 

distribution of volcanic ash from the eruption of Mount 

Galunggung, Indonesia. Analysis of the data, based on 

an understanding of the spectral emissivity properties of 

silica-rich materials, and of water clouds, resulted in 

discrimination and display of the ash cloud over a 

period of several days. These analysis procedures using 

the two thermal infrared channels of the A VHRR sensor 

are presented and discussed and the advantages of 

passive two-channel thermal infrared sensors over 

passive visible sensors, and active (Iidar and radar) 

systems are outlined. 

Intense interest in the techniques applied to this 

discrimination procedure led the author in 1982 to 

propose a two spectral channel passive thermal-imaging 

system that could be mounted in the wing of an aircraft. 

Display of the enhanced data from the imaging system 

could be multiplexed into existing aircraft avionics and 

alert the crew to the presence of silica-rich materials in 

the flight path potentially several tens to hundreds of 

kilometres in front of the aircraft, assuming clear line of 

sight. Limitations to the application of such an 

instrument were outlined at the time. The initial 

instrument design is discussed, and several 

improvements on the original concept are outlined. 

Polar orbiting satellites such as the NOAA series do 

not provide adequate or timely coverage of the areas 

prone to volcanic eruption. The twice-daily coverage of 

each of the NOAA satellites leaves extensive periods 

during which an eruption could occur, not be observed, 

and aircraft travelling through the area could be 

jeopardized. More frequent coverage is provided by the 

existing geosynchronous meteorological satellites. 

Unfortunately, these satellites lack the spectral channels 

necessary to discriminate the ash clouds from water/ice 

clouds. The author proposes that serious consideration 

be given to incorporating two thermal infrared channels 

on future generations of the GMS and GOES satellites to 

provide a capability for more frequent observation of 

eruptions. 

NEW TECHNOLOGIES TO SUPPORT 

FORECASTING VOLCANIC PLUME 

MOVEMENT 

Gary L. Hufford, National Weather Service, Anchorage, AK 

The Mt. Redoubt eruptions revealed a number of 

deficiencies in current National Weather Service 

operations that greatly hamper the forecaster's ability to 

accurately forecast and issue timely advisories on the 

movement of the volcanic debris. The forecaster lacks 

knowledge of (a) the current location of the ash both 

vertically and horizontally, (b) real-time winds near and 

downwind of the volcano, and (c) rapid access to 

volcanic-debris tracking models 

To help resolve these deficiencies, an Alaskan 

volcano-monitoring system has been designed and 

acquired. The system consists of (a) a wind profiler 

located at Homer, Alaska that provides hourly vertical 

profiles of winds near the volcano, (b) a satellite 

downlink and processing system capable of ingesting, 

processing, and displaying imagery from a variety of 

polar orbiting satellites to track ash plumes, (c) a C-hand 

radar located across Cook Inlet from Mr. Redoubt to 

provide vertical and horizontal extent of the ash plume, 

(d) and an upgrade to the regional computer and 

communications network to handle the new volume of 

data from the monitoring instrumentation described 

above. A volcanic debris tracking model has been 

developed by the NOAA Air Resources Laboratory. The 

volcano monitoring system provides the forecaster with 

vital information to generate warnings, forecasts, and 

advisories. 

ECONOMIC CONSEQUENCES OF THE 1989-90 

MT. REDOUBT ERUPTIONS: ASSESSMENT 

METHODOLOGY AND ANECDOTAL 

EMPIRICAL EVIDENCE 

Lee Huskey and Bradford Tuck, University of Alaska, 

Anchorage, AK 

The eruptions of Mt. Redoubt in the late fall and 

winter of 1989-90 resulted in major disruptions of air 

transportation, both with respect to people and freight, 

threatened the physical integrity of the Drift River oil 

terminal facility, caused the shut-down of Cook Inlet oil 

production, and in other ways caused the total 

production of goods and services in Alaska to decrease. 

The eruptions may also have caused some firms to 

reconsider south-central Alaska as a site for doing 

business. 

Volcanic Ash and Airline Safety 25 
This paper presents a methodology and design for a 

social accounting framework that structures the 

classification and regional distribution (or 

redistribution) of economic impacts attributable to the 

1989-90 Mt. Redoubt eruptions. The accounts design 

attempts to deal with several issues that arise in the 

assessment of the impacts of natural disasters. These 

include measurement of increases and decreases in 

economic activity attributable to the disaster, the 

distribution of these changes across regions, and the · 

separation of mitigation costs from direct costs of the 

disaster. The paper illustrates the use of the account 

structure with some preliminary applications of the 

methodology to specific episodes associated with the 

eruptions. 

COPING WITH THE AIRCRAFT/ASH-CLOUD 

PROBLEM IN AUSTRALIA 

R. W. Johnson, Bureau of Mineral Resources, Canberra, 

Australia and T.J. Casadevall, U.S. Geological Survey, 

Denver, CO 

Notable encounters between in-flight commercial 

aircraft and high-rising eruption clouds have taken place 

in two main regions of the world: in the Pacific 

Northeast and in the southeast Asia/southwest Pacific 

region. The belt of active volcanoes extending from 

Indonesia and the Philippines, through Papua, New 

Guinea and Vanuatu in New Zealand, represents a zone 

that international aircraft must traverse before reaching, 

or after leaving, Australia. 

Indonesia, particularly, is a formidable volcanic 

barrier consisting of almost 80 historically active 

volcanoes distributed throughout the nearly 6,000-kmlong archipelago. About 40 Indonesian volcanoes 

produced eruptions during the 1980's, the largest of 

which were from Galunggung (west Java) in 1982. Two 

Boeing 747 aircraft flying to Australia at night suffered 

multiple-engine failures as a result of nighttime 

encounters with high-rising Galunggung ash clouds, 

and a DC-9 jet on a daytime domestic flight was 

damaged. These events led to the creation by the 

Australian Department of Aviation (now the Civil 

Aviation Authority) of an Airways Volcano Watch. 

An eruption from Soputan volcano (Sulawesi) 

damaged a Qantas 7 47 aircraft en route to Melbourne in 

May 1985 (the engines surged but did not fail). This 

encounter galvanized Australian mitigation efforts that 

had been underway since 1982, through the 

establishment of the Volcanological/ Airspace Liaison 

Committee Australia-Indonesia (VULCAN). The 

26 Volcanic Ash and Airline Safety 

Australian part of this committee (VULCAN-AUS) has 

been active on four main fronts in addressing the 

aircraft/ ash-cloud problem: (1) establishing better 

communications about volcanic eruptions in the 

Indonesian region; (2) encouraging the use of satellites 

(particularly the operational GMS weather satellite) in 

the identification and tracking of eruption clouds; (3) 

participating in international efforts to provide better 

early warnings to pilots; (4) creating a Volcanic Ash 

Detection and Aviation Study Group (VADAS) whose 

task was to investigate the most appropriate 

technologies that could be used to mitigate aircraft/ashcloud encounters. CSIRO scientists, in association with 

VADAS, have devised the prototype of a small 

radiometer that could be mounted on aircraft and would 

look ahead to discriminate volcanic-eruption clouds 

from normal weather clouds. 

SEISMIC IDENTIFICATION OF GAS-AND-ASH 

EXPLOSIONS AT MOUNT SAINTT HELENS: 

CAPABILITIES, LIMITATIONS, AND 

REGIONAL APPLICATION 

Chris Jonientz-Trisler, University of Washington, Seattle, 

WA, Bobbie Myers, U.S. Geological Survey, Vancouver, 

WA, and John Power, U.S. Geological Survey, Fairbanks, 

AK 

During the past 10 years, analysis of seismic signals 

recorded by the UW /USGS Mount St. Helens network 

and correlation of these signals with observations made 

by field crews, pilots, radar operators, and the general 

public have led to the development of seismic criteria 

that enable us to identify most kinds of repetitive events 

at Mount St. Helens. Such events include volcanic 

earthquakes, tremors, rockfalls, debris flows, domebuilding eruptions, gas-and-ash explosions, and many 

types of cultural noise. Identification criteria are based 

on comparisons of signal envelopes, dominant 

frequencies, and relative amplitudes and timing among 

stations. 

In general, gas-and-ash explosions at Mount St. 

Helens are characterized by emergent, low-frequency 

signals of extended duration, often with pulsating 

amplitude changes. Relative amplitudes are similar 

among stations on the flanks of the mountain but are 

much higher at stations within the crater. Several factors 

may complicate signal identification. These include 1) 

changes in the volcanic processes generating the 

explosions, 2) overlap of signals from closely spaced 

events, and 3) the temporary loss of key stations. 
Nevertheless, we have had considerable success 

identifying explosions within minutes of their 

occurrence. 

The University of Washington also operates seismic 

stations or mini-networks at or near most other Cascade 

Volcanoes in Washington and Oregon. When future 

seismicity increases significantly at one of these 

volcanoes, the local network will be enhanced to 

improve monitoring capabilities. The criteria used to 

identify gas-and-ash explosion signals at Mount St. 

Helens and the techniques used to develop these criteria 

will provide a strong foundation for signal identification 

at other active volcanoes. 

PREDICTION AND DETECTION OF 

EXPLOSIVE ERUPTIONS AT SAKURAJIMA 

VOLCANO, JAPAN 

Kosuke Komo, Kazuhiro Ishihara, Sakurajima 

Volcanological Obseroatory, Japan and Makoto Tahira, 

Alichi University of Education, Japan 

The volcanic activity of the explosive summit 

eruptions has continued since 1955 at Sakurajima 

volcano, Kyushu, Japan. The frequency of the explosive 

eruptions amounts to more than 6,000 during the last 35 

years. The explosions at the summit crater can be 

predicted by the tilt and strain data at the summit area 

and the swarms of the shallow earthquakes generated 

beneath the active crater. The onset of explosions are 

detected by the explosion-quakes, the air-shocks 

accompanied with them, and the visual erupting images. 

The success rate of the Automated Warning System for 

the actual eruptions is more than 70 percent. The 

detecting system for volcanic eruptions by the infrasonic 

air-waves with microphones array at Kariya, Nagoya, 

710 km away from the volcano, has the capability to 

detect the air-waves generated by volcanic eruption 

which occurred at the volcanoes a thousand and several 

hundred km distant. A world-wide network system for 

detecting the air-waves from volcanic explosions will be 

useful to acquire the information of location where the 

eruption occurs and of estimating the magnitude of the 

eruptions. The system should be very effective to 

aviation safety similar to Tsunami Warning System 

which is operating world-wide. 

FORECASTING VOLCANIC DEBRIS IN 

ALASKA 

Lee Kelley, National Weather Seroice, Kodiilk, AK 

The Center Weather Service Unit (CWSU) of the 

National Weather Service has the responsibility to 

provide forecasts that insure smooth flow of air traffic 

into and out of Alaska. The Mt. Redoubt eruption 

presented a number of problems to the region. 

Numerous explosive episodes caused significant 

damage to aircraft, severely disrupted air traffic, and 

resulted in airports closing operations. 

The major forecast problem centers around a lack of 

information concerning plume characteristics: (1) lack 

of ash particle size and concentration; (2) no current ash 

location; and (3) lack of real-time winds near and 

downwind of the volcano. The forecaster is forced, for 

safety sake, to include a large hazardous zone around 

the estimated trajectory of the ash for aircraft to avoid. 

This can cause unnecessary delays to travel around the 

zone when most of it is ash free. 

To assist the aviation community in their need for 

information on ash distribution, the CWSU generated an 

ash-trajectory plot with 4 hour movement of the ash 

plume. This plot was updated as new information 

became available. The biggest source of information 

was from pilot reports. This plot was distributed to over 

90users. 

VOLCANIC AIR-AIRCRAFT 

INCIDENTS IN ALASKA IN THE 

YEARS PRIOR TO THE DECEMBER 15, 

1989 747 REDOUBT ENCOUNTER 

Juergen Kienle, University of Alaska Fairbanks, Alaska 

Commercial and military aircraft have encountered 

volcanic ash in the Cook Inlet basin on three other 

occasions besides the most recent events near Redoubt 

Volcano in 1989/90. Over the past 36 years, aircraft 

have met volcanic ash plumes on four occasions, three 

times in the past 13 years alone, resulting in a variety of 

technical problems. No crashes or deaths resulted from 

these encounters so far. 

Mt. Spurr 1953: A short one-day eruption of Mt. 

Spurr, 120 km west of Anchorage, caused heavy ash falls 

that lasted for three hours from noon until 3 p.m. 

Maximum plume heights were about 21 km (70,000 ft.) 

and extensive lightning was observed by L. Metzner. 

Twenty-six aircraft of the Air Force's 5039th Air 

Transport Squadron were evacuated to Laird and 

Volcanic Ash and Airline Safety 27 
Eielson Air Force Bases near Fairbanks. Three aircraft 

flew through the ash plume resulting in sandblasted 

leading edges, windshields, side panels and front 

portions of the canopies, reducing pilot visibility. Most 

planes remaining in Elmendorf were hangared in time, 

except for several large C-124 transport aircraft (Globe 

Trotters). These required ten days of clean-up for the 

removal of the fine volcanic ash. The lOth Division had 

completely lost its capability of meeting an air defense 

mission between July 9 and 13. It was only on 17 July 

that the three Elmendorf fighter-interceptor squadrons 

returned to normal operations 

I have found no information whether or not 

commercial aircraft were affected at Anchorage 

International Airport or elsewhere in Cook Inlet. 

Mt. St. Augustine 1976: Mt. St. Augustine erupted in 

January 1976, after 12 years of dormancy. Subplinian 

eruptions occurred from January 22 to 26 and spread ash 

generally northward and eastward over the Kenai 

Peninsula with fine ash falling as far away as Sitka, 1,100 

km downwind. 

On January 22, two F-4E Phantom jets on a flight 

from Galena to King Salmon intercepted an ash plume at 

1430 AST. The pilot reported instant, complete darkness 

in the cloud. No engine failure occurred. Upon landing 

at King Salmon, the canopy of the aircrafts were 

scoured, and the paint at the wind tips was sandblasted 

off. Very fine jewelers rouge-colored material was 

ingested into the cockpit through the engine air intake. 

The material was sticky and was found in every "nook 

and cranny" of the planes. 

On January 25, cargo flight JL672, a DC-8, entered an 

Augustine ash cloud near Whitefish Lake, 25 km 

southeast of Sparrevohn. Upon landing in Tokyo, the 

scoured center windshield had to be replaced; much ash 

had adhered to the plane. Slight abrasion damage was 

found on external radio parts, landing gears and the airconditioning system, but none of these parts needed to 

be replaced. 

Two other passenger planes, a Boeing 747 and a DC8, also bound for Tokyo and departing within one hour 

after flight JL672, reported ash suddenly adhering to the 

planes near Sparrevohn which caused minor damage, 

but not as extensive as that to the DC-8 of flight JL672. 

Mt. St. Augustine 1986: Airborne ash disrupted 

aircraft operation throughout the Cook Inlet basin 

during the 1986 eruption. Early in the morning of March 

27, with the eruption just beginning, the Air Force 

evacuated most of their planes from Anchorage and kept 

them away until March 30. Air carrier service at 

Anchorage was nearly at a standstill March 27-29. 

Alaska Airlines canceled 40 Anchorage arrivals and 

departures out of 68 scheduled operations on March 28. 

Western Airlines canceled its entire schedule of flights to 

28 Volcanic Ash and Airline Safety 

and from Alaska march 27 and 28 and flew only a partial 

schedule on March 29. United canceled 35 Alaska flights 

between March 27 and 29. No serious disabling ash 

encounters occurred during this time. 

GENERATION AND DISTRIBUTION OF 

GRAPHICAL DEPICTIONS OF VOLCANIC 

ASH PLUMES 

Herschel Knowles, National Weather Service, Alaska 

The Mt. Redoubt eruption episodes showed that 

National Weather Service (NWS) products on volcanic 

debris were most effective when distributed in graphical 

form. At the beginning of the eruptions, most of the 

products generated were either in alphanumeric form or 

hand drawn graphics. The graphical presentations were 

then distributed by slow telefax. The aviation 

community found the graphical depictions of ash 

plumes to be very valuable. The list of users rapidly 

grew to over 90. The slow-telefaxing method was found 

insufficient for distribution. 

The Federal Aviation Administration (FAA), the 

primary user of the graphic products, provided a digital 

graphics system that allowed for rapid interactive 

generation and distribution of predicted volcanic plume 

trajectories to many users in the aviation community. 

The NWS reaction to future eruptions and use of the 

graphics-distribution system is described in detail. 

VOLCANIC HAZARDS VIDEO 

M. Krafft, Centre de Volcanologic Volcain, Cernay, France, 

S.R. Brantley, U.S. Geological Suroey, Vancouver, WA, and 

C.G. Newhall, U.S. Geological Suroey, Reston, VA 

Volcanic eruptions vary widely in type, magnitude, 

and effects. The hazards associated with eruptions, 

however, are not well understood by most people. The 

principal types of volcanic activity that can adversely 

affect people and property include ash falls from ash 

clouds, ash flows, mudflows, volcanic landslides, 

volcanic tsunamis, lava flows, and volcanic gases. Of 

these hazards, ash clouds are the primary hazard to 

aviation safety. People living near volcanoes are more 

likely to take steps to avoid the deadly consequences of 

eruptions if they understand the hazards associated with 

these types of volcanic activity. Toward this end, a 

videotape has been produced that ~amatically shows 

the destructive power of volcanic activity. Spurred by 

the eruption of Nevado del Ruiz (Columbia) in 1985 
(more than 22,000 people were killed by mudflows), the 

International Association of Volcanology and Chemistry 

of the Earth's Interior (lA VCEI) sponsored production of 

the video program Understanding Volcanic Hazards in 

cooperation with the United Nations Educational 

Scientific and Cultural Organization, the United States 

Geological Survey, and other national organizations. 

The videotape will be available through lA VCEI in a 

variety of video formats and languages, including 

English, Spanish, Italian, Indonesian, and Japanese. 

VOLCANIC-HAZARD DETECTION WITH 

TOMS 

Arlin J. Krueger, Louis Walter, Charles Schnetzler, Scott 

Doiron, and Gregory Bluth, NASA, Greenbelt, MD 

The Total Ozone Mapping Spectrometer (TOMS) 

instrument is capable of unique identification of volcanic 

eruption clouds from space. This capability can aid in 

location of aviation hazards associated with volcanic ash 

during the early phases of an eruption and with sulfate 

aerosols during later phases of the eruption cloud. The 

instrument is presently flying in a polar orbit on the 

Nimbus 7 spacecraft. Four more instruments are 

scheduled to be launched on new Soviet, American, and 

Japanese polar orbiting spacecraft during the next six 

years. NOAA operational satellites will carry additional 

instruments during the next decade. A conceptual 

design study has been conducted on a geostationary 

TOMS instrument. Such an instrument would provide 

time resolutions of 15 minutes compared with 24-hour 

resolution from polar-orbiting satellites. 

The technique makes use of the absorption of 

sunlight by sulfur dioxide, a gaseous constituent of 

volcanic plumes, at near-ultraviolet wavelengths, which 

are used for ozone mapping. A data-processing 

algorithm separates the ozone and sulfur dioxide 

quantities. The instrument produces full global surveys 

of ozone and sulfur dioxide each day with ground 

resolutions of about 50 km. 

The 35 volcanic eruptions detected with TOMS since 

1978 include Mount St. Helens, El Chichon, Alaid, 

Nyamuragira (Zaire), Galunggung, Una Una, Ruiz, 

Redoubt, Hekla, and several volcanoes in the Galapagos 

Islands. Research is underway to improve the detection 

algorithm and to understand the variations of sulfur 

dioxide in eruption clouds. 

MITIGATION OF THE EFFECTS OF VOLCANIC 

ASH ON AIRCRAFf OPERATING AND 

SUPPORT SYSTEMS 

John R. Labadie, JA YCOR, Alexandria, VA 

On 18 May 1980, Mount St. Helens erupted, covering 

50% of Washington with approximately 1 km3 of ash. 

Government agencies, airports, utilities, and private 

corporations within the affected areas were all forced to 

cope with ash deposits (ranging in depth from 3 mm to 

75 mm) in maintaining essential services and in carrying 

on normal activities. In-depth interviews with 

equipment users, service companies, airport operators, 

utilities, and others affected by the ash elicited detailed 

information on ash-related damage and on mitigation 

methods. 

Volcanic ash is abrasive, mildly corrosive, and 

(especially when wet) conductive. Also, it may carry a 

high static charge for up to two days. The ash is finely 

divided, easily entrained in the air by wind or vehicle 

movement, and may remain suspended in the air for 

many minutes. Due to the combination of these 

qualities, volcanic ash is pervasive. It can penetrate all 

but the most tightly sealed enclosures and can be very 

difficult to remove from electronic components. 

The ash easily absorbs water and can weigh up to 

1,400 kg/m3; water laden ash may collapse or damage 

flat roof. Wet ash is very slippery and can cause traction 

problems. Dry ash blown into the air reduces visibility 

and piles up on roads, runways, and taxiways. Ash 

must be physically removed and controlled after 

removal to prevent re-entrainment. Ash deposited on 

electronic components can cause arcing, short circuits, 

and intermittent failure due to its conductive nature. 

High-voltage circuits and components are especially 

vulnerable. Ash dampened by rain can cause arcing, 

flashovers, and pole fires on electrical-distribution 

systems. Resulting outages may hamper mitigation 

techniques that require electrical power. 

Techniques for reducing the effects of volcanic ash 

are basically "low tech" and can be grouped into three 

broad categories: keeping the ash out, controlling what 

gets in, and disposing of the ash. Mitigation actions will 

be required on a continuous basis as long as ash is 

present. Settled ash is easily re-entrained, and 2 mm 

layer can be as troublesome as a 50 mm layer. 

The most effective technique for reducing ash-related 

damage or upset to equipment is to avoid using it: shut 

down, close up, keep inside, or seal off until the ash can 

be removed. Unfortunately, this tactic is acceptable only 

for short periods of time; operations must be resumed at 

Volcanic Ash and Airline Safety 29 
some point. Effective mitigation depends on prior 

planning and preparation, mobilization of resources, 

and persistence. 

VOLCANIC PRODUCTS AND AVIATION 

SAFETY: MODELING THE GAS-PARTICLE 

CONVERSIONS 

F. LeGuern, CEN-Saclay, Gif sur Yvette, France, and A. 

Bernard, Universite Libre, Brussels, Belgium 

Volcanic plumes are mainly formed of fine grains of 

exploded rock: "volcanic ash". Plumes also include 

solid and liquid aerosols resulting from cooling and 

condensation of the high-temperature eruptive gases, 

which contain acids, halogens and metals. Aerosols can 

be both free or absorbed on the ash surface. Free 

volcanic gases can persist in the cold plume for hours 

before dilution; aerosols can persist for days. 

A high-temperature volcanic-gas cooling model has 

been developed and will be used to predict the 

composition of volcanic aerosols. The model was tested 

using the examples of Mt. Etna and Mount St. Helens. 

Mt. Etna gases contained H20=91.9, H2=0.7, C02=1.4, 

C0=0.0007, 502=2.8, H2S=0.6, HCI=2.5, HF=0.5, NA= 

1.2, K=1.2 plus 19 other trace elements detected (as 

collected at 928°C at the source of a side lava flow). 

Mount St. Helens contained H20=98.6, H2=0.4, 

C02=0.88, C0=0.002, 502=0.067; H2S=0.09, HCI=0.07, 

HF=0.02, Na 0.0004, K=0.0003 plus 40 other elements 

detected (as collected in the crater at 710°C. 

In both cases, plumes are very acid rich, but on Etna 

the plume is very rich in NACI and KCI; H2S is oxidised 

to S gas and converted into metallic sulfurs. On Mt. St. 

Helens, NA and KCI are 1000 times less abundant and 

502 is oxidised to form elemental solid sulfur. These 

reactions occur in a few seconds when the magmatic 

gases enter the atmosphere, then slower reaction of 

oxidation will occur in the cold plume taking a few 

hours or days. This mixture of gas, ash and aerosols can 

be sintered in the engine by heating, compressing and 

dehydration. It can affect the windshields or 

contaminate the kerosene. 

However, the great variability of the actual volcanicgas source composition makes it very difficult to predict 

the actual volcanic-plume composition before having 

samples from the source itself. The modeling makes it 

possible to predict the behaviour of different 

hypothetical gas mixtures starting with 20 elements and 

considering 900 final products. 

30 Volcanic Ash and Airline Safety 

MOUNT REDOUBT: TRACING VOLCANIC 

ASH PLUMES FROM SPACE 

James S. Lynch, National Oceanic and Atmospheric 

Administration, Washington, D.C. 

Volcanic ash and debris are extremely hazardous to 

aircraft, with several craft experiencing nearcatastrophic inflight damage as a result of flying through 

the debris. To respond to these potentially catastrophic 

events, the Federal Aviation Administration (FAA) and 

National Oceanic and Atmospheric Administration 

(NOAA) have established a cooperative Volcano 

Hazards Alert Program. The program encompasses all 

volcanic debris reaching at least 5 km altitude within 

U.S. airspace or international airspace designated as a 

U.S. Flight Information Region (FIR). 

Upon detection or notification of an explosive 

volcanic eruption, NOAA's National Environmental 

Satellite, Data, & Information Service (NESDIS) has the 

responsibility to coordinate information (i.e., satelliteimagery analyses, trajectory forecasts, pilot report 

summaries, etc.) directly to primary FAA and NOAA 

facilities responsible for flight safety and warnings, 

including: NWS Meteorological Watch Offices, NWS 

National Aviation Weather Advisory Unit, National 

Meteorological Center, and FAA Central Flow Control 

Facility. These primary facilities have the responsibility 

of issuing "significant meteorological warnings" 

(SIGMET) to all aviation interests. 

Mount Redoubt in Alaska began a series of explosive 

volcanic eruptions on 14 December 1989. Since the 

initial event, geostationary and polar-orbiting 

environmental satellites have been used to track ash and 

volcanic debris from over twenty eruptions of Redoubt. 

During the 15 February 1990 eruption, a pyroclastic 

surge resulting in a serious mudflow along the Drift 

River was detected in "real time" using A VHRR HRPT 

data, and timely warnings were issued to the 

hydrologist in Anchorage, Alaska. Multispectral 

imaging from polar spacecraft offers enhanced potential 

for monitoring ash plumes, even when debris is not 

apparent using single-channel visible or infrared data. 

This paper briefly reviews the history of volcanic ash 

tracking in NESDIS (dating back to Mount St. Helens in 

1980), the recent history of Mount Redoubt, and analysis 

techniques being planned and implemented. 
STATISTICAL APPROACH IN ASSESSMENT 

OF VOLCANIC HAZARD FOR AIR TRAFFIC: 

AN APPLICATION TO VESUVIUS 

G. Macedonio, Centro di Studi per la Geologia Strutturale e 

Dinamica dell 'Appennino, Pisa, Italy, Papale, Instiuto 

Nazionale di Geofisica, Roma, Italy, M. T. Pareschi, Centro 

Ricerca IBM, Pisa, Italy, and M. Rosi and R. Santacroce, 

Dipartimento di Scienze della Terra, Pisa, Italy 

Release and dispersion of ash as a consequence of 

plinian or subplinian eruptions could seriously affect 

flights in the proximity of a volcano. We present a 

method to quantify hazard for flights so that realistic 

measures can be adopted, such as planning and 

designing for engineering systems to prevent the 

absorption of volcanic particles into engines. An 

example is presented for Vesuvius (Italy). The expected 

eruption (Macedonio et al., 1990, J. Volcano. and Geo. 

Res. 40, p. 327-342; Barberi et al., 1990, Nature, 334, p. 

142-144) is taken into consideration for this volcano and 

a numerical model (Armienti et al., 1988, JGR, 96, B6, p. 

6463-6476; Macedonio et al., 1988, JGR, 93, B12, p. 14817-

14827) is used to compute ash concentration in the air. 

Eruption durations (Te = 3h, 12h, 24h) are considered 

and, for each . case, four subcases are analyzed: 

co?centra~on in the a.ir at times t- 0.5Te, Te, 1.5Te, 2Te. 

Wtnd profiles (3125 different ones), recorded in the past 

years in the region, have been used in the simulations. 

More exactly for each time (for example: t = Te), for each 

duration (for example: Te = 12h) and for each wind 

profile, spatial ash distribution is computed. Letting t 

and T e unchanged, the surfaces corresponding to 

isoprobability to have concentration greater or equal to 

given thresholds are computed, as obtained by using all 

the past available wind profiles. The directions and 

heights of ash clouds in a range of a few hundred 

kilometers around the volcano are then outlined. 

USE OF METEOROLOGICAL SATELLITES FOR 

DETECTING AND TRACKING VOLCANIC 

CLOUDS 

Michael Matson, NOAA/NESDIS, Washington, D.C. 

Meteorological satellite data have been used to detect 

volcanic eruptions and monitor the subsequent ash 

clouds since 1976. Imagery and digital data can be used 

in conjunction with conventional radiosondes to 

determine the altitude of a volcanic eruption, the size, 

speed, and position of the ash cloud, and the direction 

the ash is moving. However, it can be difficult to 

distinguish a volcanic ash cloud from meteorological 

clouds due to similar spectral characteristics. Work was 

done to distinguish the two using multispectral 

techniques. Currently there are four geostationary 

meteorological satellites providing global coverage 

between latitudes 60N and 60S using visible and thermal 

infrared sensors. There are also several U.S. and Soviet 

polar-orbiting meteorological satellites with visible and 

thermal infrared sensors that provide daily global 

coverage and multiple overpass times over all volcanic 

areas. Using these satellites and enhanced detection 

techniques, it is possible to operationally monitor 

volcanic eruptions for any part of the Earth. 

THE SMITHSONIAN'S GLOBAL VOLCANISM 

NETWORK: FACILITATING 

COMMUNICATION OF ERUPTION 

INFORMATION 

Lindsay McClelland, Smithsonian Institution, 

Washington, D.C. 

The Smithsonian Institution's Global Volcanism 

Network (formerly SEAN, the Scientific Event Alert 

Network) has gathered and disseminated information 

about the world's volcanic activity since 1975. In the 

succeeding 15.5 years, GVN has reported activity at 

more than 275 volcanoes, including history's smallest 

recorded eruption, which ejected 26m3 of lava from an 

Icelandic geothermal borehole in 1977, the globe-circling 

stratospheric cloud produced by Mexico's El Chichon in 

1982, and Colombia's tragic Ruiz eruption that killed 

more than 20,000 people. Information is provided by a 

worldwide network of about 1500 correspondents -

scientists, government officials, airplane pilots, and 

others with knowledge of volcanic activity - who 

receive a monthly Bulletin. The Bulletin is available by 

subscription through the American Geophysical Union, 

on electronic mail systems OMNET and 

KOSMOS/Pinet, and summaries are published in 

Bulletin of Volcanology, EOS, and Geotimes. Scientists and 

officials are quickly notified of eruptions that provide 

significant opportunities for research and/or threaten 

life and property. 

News of an eruption that may affect aviation is 

immediately forwarded to NOAA's satellite service and 

the Federal Aviation Administration. Local 

volcanologists are consulted for information about the 

eruption, and Smithsonian resources are searched for 

data about the volcano's geography and eruption 

history. Observations from satellites and aircraft are in 

turn forwarded to volcanologists studying the eruption 

Volcanic Ash and Aviation Safety 31 
and to the officials responsible for the safety of people 

living nearby. Only by exchanging information among 

many sources -- volcanologists, abnospheric scientists, 

satellite observers, pilots, and air-traffic control facilities 

-- will the necessary perspective be available to the 

officials who must make informed decisions about the 

response to an eruption. Improved communications are 

needed to facilitate information exchange. For example, 

geologists presently have no direct, rapid access to 

volcano-related Notices to Airmen and pilot reports of 

eruption clouds. Assessment of the threat posed by 

volcanoes to air traffic is also hampered by the lack of 

maps that combine volcano locations with air routes. 

Interagency and interdisciplinary cooperation should be 

able to solve these and other problems, even in a time of 

limited funding. 

VOLCANIC-TREMOR AMPLITUDE 

CORRELATED WITH ERUPTION 

EXPLOSIVITY AND ITS POTENTIAL 

APPLICATION FOR A VOLCANIC-ASH 

WARNING SYSTEM 

Stephen R. McNutt, Sacramento, CA 

New data on volcanic-tremor amplitudes define an 

empirical relation between tremor amplitude and 

eruption explosivity: as the explosivity increases, the 

tremor amplitude increases. Tremor data for over 50 

volcanoes were normalized to their reduced 

displacement amplitudes, thereby permitting 

quantitative comparison. Amplitudes for a well-studied 

subset of data were compared with eruption styles 

yielding the following (in order of increasing 

explosivity): hydrothermal, 0.05-5 cm2; strombolian, 2-

30 cm2; vulcanian/pelean, 20-150 cm2; and plinian, >100 

cm2. The eruption styles overlap with each other, and, 

similarly, the tremor amplitudes overlap. Thus, tremor 

amplitudes alone cannot unambiguously define 

eruption styles, but clearly the amplitudes increase with 

increasing explosi vity. 

A rapid assessment of the explosivity could help 

determine hazards from airborne ash. Thus, tremor 

amplitudes could help form the basis of a warning 

system. The tremor amplitudes are recorded in real time 

as the volcanic materials exit the vent. It then takes 

many seconds to several minutes for the ash to reach 

altitudes where it would pose a hazard to aircraft. 

Therefore, tremor amplitudes could help determine the 

size of an eruption and the amount of ash before the ash 

reached hazardous altitudes. Tremor duration could be 

used to estimate the likely duration of an eruption. This 

32 Volcanic Ash and Aviation Safety 

information, coupled with information on wind speed 

and direction, would significantly improve the 

capabilities of a near-real time semi-automated volcanicash warning system. 

VOLCANIC ASH FROM THE EXPLOSIVE 

ERUPTIONS IN KAMCHATKA AND KURILES 

AS A SOURCE OF POTENTIAL HAZARD FOR 

AVIATION 

I. V. Melekestsev, 0. A. Braitseva and V. Yu. Kirianov, 

Institute of Volcanology, Petropavlovak-Kamchatsky, USSR 

Twelve volcanic eruptions of different types 

(Ksudach, Bezymianny, Shiveluch, Tolbachik and other 

volcanoes) taking place in the 20th century and having a 

volume of erupted pyroclastics of up to 2 km3 and the 

range of tephra dissemination of several hundred or 

thousand kilometers, were studied in detail. More than 

20 analogous and larger eruptions have been established 

to occur during the last 10,000 years. Data on the 

distribution, volume, chemical composition, mineralogy 

and grain size have been obtained for volcanic ash 

generated by historic and prehistoric eruptions. Studies 

on the dynamics of the eruptive clouds have shown that 

a considerable part of the volcanic ash was transported 

towards the Pacific Ocean. 

The data obtained can be used as a model for 

calculating the movement of eruption clouds of future 

eruptions and for providing aviation safety in the region 

of the Northern Pacific. 

VOLC.ANIC ASH AND AIRCRAFT 

OPERATIONS 

Edward Miller, Air Line Pilots Association, Herndon, VA 

The aviation community has been subjected to 

volcanic eruption hazards on several occasions over the 

years, usually in rather dramatic fashion. Volcanic dust, 

a by-product of many volcanoes, though not all of them, 

is often injected into the stratosphere with an explosive 

eruption and is left to spread laterally in the upper level 

flow. The dust is abrasive and capable of causing 

serious damage to aircraft engines, control surfaces, 

windshields and windows, and landing lights. The dust 

can also clog the pitot static systems that help calculate 

airspeed and altitude for the pilots, and it can damage 

sensors that deliver electronic data to automated 

systems used to fly modem aircraft. Mixed with 
weather-associated clouds, the ash becomes difficult and 

sometimes even impossible to identify. 

Recent events have reminded us with alarming 

regularity that aircraft and volcanic ash do not mix. 

Windshields have been rendered opaque, engines have 

failed, and severe damages have left air carriers with 

aircraft useless to them without costly repair. Most 

recently, the Boeing 747-400 of a Dutch airline 

encountered volcanic ush from the \edoubt Volcano in 

Alaska and suffered a simultaneous four-engine 

flameout. The most advanced example of that aircraft 

type was an expansive glider for several minutes, 

despite its state of the art technology. 

This paper will explore the surface detection, 

reporting, and dissemination of information critical to 

crew members operating in the vicinity of known 

volcanoes. It will also discuss other operational needs of 

flight crew members. Pilots need to be educated about 

hazards of volcanic ash. Pilots need two tools in coping 

with volcanic ash: a copy of the ICAO Volcanic Activity 

Reporting Form and a chart portraying air routes and 

locations of known volcanoes. This chart is not yet 

available. 

THE 1989-90 ERUPTION OF REDOUBT 

VOLCANO: CHRONOLOGY, CHARACTER 

AND EFFECTS 

T. P. Miller, U.S. Geological Suroey, Anchorage, AK and 

J. N. Davies, University of Alaska, Fairbanks, AK 

Redoubt volcano, a remote 10,200-foot-high 

stratovolcano 110 miles southwest of Anchorage, began 

its third major eruption this century on December 14, 

1989. An initial eruptive phase (December 14-19) 

consisted of numerous and repeated vent-clearing 

explosive events that generated ash-rich eruption 

columns rising to over 40,000 feet. Airborne ash 

generated by these events was carried by prevailing 

winds east and north toward the populous parts of the 

Cook Inlet region shutting down air traffic for 3 days. 

On December 15, a 747 jet passenger airliner lost all 4 

engines after encountering an ash cloud 80 miles north 

of Anchorage; the engines wee later restarted and the 

aircraft landed safely. The second phase of the eruption, 

consisting of episodic lava dome emplacement (similar 

to Mount St. Helens) and destruction, began on 

December 22: 13 such lava domes were emplaced over 

the next 120 days. Each was destroyed by brief (<20 

minute) explosive events that produced ash clouds 

which also effected air traffic but for a much shorter time 

than in the initial phase. 

Alaska Volcano Observatory, through its seismic 

monitoring network and field observations, recorded all 

of the explosive eruptions and predicted several of them. 

Eruption notification and hazards were communicated 

to the airline industry through an agency call-down list, 

daily updates, and a color-coded hazard alert. 

Six major explosive eruptions have occurred from 

Redoubt and neighboring Spurr and Augustine 

volcanoes in the past 38 years. All three of these Cook 

Inlet volcanoes are now monitored seismically so that 

their future eruptions can be reported immediately and 

in some cases predicted. West of Cook Inlet, the 39 

active volcanoes that occur spaced along a 1500-milelong arc from the Alaska Peninsula through the Aleutian 

Islands (and average one eruption per year) are not 

presently monitored. These otherwise remote volcanoes 

do, however, present a continuing hazard since several 

great circle air routes parallel or cross this arc. 

NOAA'S RESPONSE TO THE MOUNT 

REDOUBT ERUPTIONS OF DECEMBER 1989 

Anthony Mostek, NOAA/National Weather Service, Silver 

Spring, MD 

The National Oceanic and Atmospheric 

Administration (NOAA) is responsible for monitoring 

the ejection of volcanic ash into the atmosphere and the 

subsequent forecast of where the ash is likely to be 

dispersed. NOAA's National Environmental Satellite, 

Data, and Information Service (NESDIS) is responsible 

for the monitoring of an notification of ash eruptive 

events in real-time. NOAA's National Weather Service's 

(NWS) responsibility is to provide forecast information 

on the location and predicted track of volcanic ash. This 

guidance is provided in real-time through the issuance 

of Significant Meteorological Messages (SIGMETs) by 

NWS forecasters. NOAA's responsibility is stated in the 

memorandum of understanding between the Federal 

Aviation Administration and NOAA on Volcanic 

Hazards Alert. 

As shown by the KLM event on December 15, the 

ability to monitor and forecast the volcanic-ash cloud 

dispersion in the atmosphere was inadequate. NOAA 

was asked to review the situation and generate a 

proposal for improving the volcanic-ash monitoring and 

forecast program. NOAA was able to pull together its 

various elements and generate a proposal within a few 

weeks. The Alaska Volcano Project consists of various 

components: new observing capabilities, new computer 

and communications equipment, and studies to enhance 

the numerical modeling systems. The presentation will 

Volcanic Ash and Aviation Safety 33 
provide a review on the progress of the Alaska Volcano 

Project. 

USING A PERSONAL COMPUTER TO OBTAIN 

PREDICTED PLUME TRAJECTORIES DURING 

THE 1989-1990 ERUPTION OF REDOUBT 

VOLCANO, ALASKA 

T.L. Murray, U.S. Geological Survey, Vancouver, WA, 

C.I. Bauer, National Weather Service, Anchorage, AK, and 

J.F. Paskievitch, U.S. Geological Survey, Anchorage, AK 

The Alaska Volcano Observatory (AVO) and the 

Anchorage Weather Service Forecast Office (WSFO) 

daily obtain predicted plume trajectories (PPTs) for 

Redoubt Volcano, Alaska. Data for the PPTs are 

produced on a National Oceanic and Atmospheric 

Administration NAS/9000 computer. It models 

measured and forecasted winds to predict the path of a 

weightless-particle release at various pressure altitudes 

above a specified location. The paths are assumed to 

indicate the general direction and speed that ash from an 

eruption at that location will travel. 

In response to the Redoubt eruption, we 

programmed an IBM AT-style computer to dial the 

NAS/9000 and obtain the PPTs. The program enables 

AVO and WSFO to easily collect the day's PPTs each 

morning. Thus, the PPTs are immediately available in 

the event of an eruption later in the day. The PPTs are 

plott~d on a map of Alaska, showing the predicted 

location of the ash at three-hour intervals for different 

altitudes between 5k and 53k feet. The plots are easily 

telefaxed to interested parties. The program has been 

modified to enable the user to obtain PPTs for other US 

volcanoes. 

AIRBORNE RADAR DETECTION OF 

VOLCANIC ASH 

Mark E. Musolf, Norden Systems, Norwalk, Connecticut 

Detection of volcanic-ash clouds is highly desirable 

bJ:' both ground-based and airborne radar systems. 

Auborne radars would provide coverage in regions 

where ground-based radar coverage is not available, 

allowing for real-time pilot reaction to a potentially 

dangerous situation. Present airborne weather radars 

are inadequate for detection of volcanic-ash particles or 

clouds due to the power/aperture and sensitivity 

limitations of these systems. 

34 Volcanic Ash and Aviation Safety 

This paper will analyze three different airborne radar 

configurations, X-Band (9.5 GHz), Ku-Band (16 GHz) 

and millimeter (95 GHz), to determine their effectiveness 

for detection of volcanic ash. Volcanic-ash cloud 

detection and signal-to-noise ratio will be evaluated as a 

function of operating frequency, radar cross section, 

range, and azimuth angle. Along with performance 

evaluation, antenna parameters (gain, beamwidths and 

sidelobes) and waveform parameters (PRFs, 

pulsewidths and coding) will be developed. 

The practicality of modifying existing airborne radars 

to improve their detection capability will be addressed. 

Limitations of an airborne radar based on hardware 

constraints will be discussed. The paper will also 

identify advances in technology that will improve 

volcanic-ash detection in future radar systems. Recent 

advances in radar technology developed for the 

detection of low observable targets will be considered. 

VOLCANIC-EVENT NOTIFICATION AT 

MOUNT ST. HELENS 

Bobbie Myers, U.S. Geological Survey, Vancouver, WA and 

George J. Theisen, USDA Forest Service, Vancouver, WA 

During the 1980-86 eruptions of Mount St. Helens, 

hazard information was quickly disseminated through a 

U.S. Geological Survey /USDA Forest Service 

notification system. Written and verbal statements 

issued jointly by the U.S. Geological Survey and 

University of Washington were released to the Forest 

Service for telephone call-down to governmental 

agencies and private interests. These statements were 

also entered into a computer-information system 

accessible to agencies on the call-down list. Once the 

call-down was in progress, public- and mediainformation tapes were updated and press releases 

issued. Since most of these eruptions had recognizable 

precursors, a series of information statements and 

eruption forecasts was issued during the weeks to hours 

before an eruption, providing advance warning of 

volcanic activity and associated hazards. 

Hundreds of small gas and ash emissions also 

occurred during 1980-86, most without recognizable 

precursors. The lack of precursors made advance 

warning of these events impossible; instead, information 

statements were issued after the larger, more visible 

events. When small emissions were frequent, the 

possibility of more small emissions was stressed. 

However, when these events were infrequent, 

governmental agencies and the public were often 
surprised and frustrated by the lack of instantaneous 

information. 

The occurrence of occasional small, unpredictable 

ash-producing explosions at Mount St. Helens during 

1981-1991, coupled with increased concern about the 

hazards of volcanic ash to aviation, prompted CVO to 

develop a seismic-alarm system that triggers on small 

volcanic events. This alarm system activates CVO's 24-

hour beeper. In addition, the Federal Aviation 

Administration (FAA) can call the beeper to report 

possible volcanic activity. These two modifications 

should decrease CVO's response time for nonpredictable, sudden-onset events and help the FAA 

quickly verify pilot reports of possible volcanic plumes. 

VOLCANOES AND ATMOSPHERIC 

TEMPERATURE 

Reginald E. Newell, MIT, Cambridge, MA 

The eruption of Mount Agung in 1963 produced 

increases in tropical stratospheric temperature measured 

with radiosondes of about 6°C with possible decreases 

in the tropical troposphere of about 0.5°C. The sudden 

temperature increases were the largest in that region 

since radiosonde records began in the early 1950's. The 

pattern of aerosol-induced temperature change in a 

latitude-height plane was similar to that of the pattern of 

radioactive dust from nuclear weapons' tests; both are 

controlled by the large-scale mean and eddy motions in 

the lower stratosphere. The eruption of El Chichon in 

Mexico in 1982 produced an aerosol cloud with similar 

extent and was also accompanied by an increase in 

tropical stratospheric temperature. In addition to 

radiosonde data, satellite data from microwave 

sounding units (MSU) was available for El Chichon and 

verified temperature increases for the lower 

stratosphere. This paper reviews observational studies 

of volcanic clouds and temperature changes carried out 

since the eruption of Agung engendered interest in this 

topic and raises the question: can significant 

information about the extent o1· volcanic clouds in the 

lower stratosphere be obtained from MSU data? 

AVIATION SAFETY FOR ASH CLOUDS IN 

JAPAN AND JAL'S SYSTEM FOR 

SAKURAJIMA'S ERUPTIONS 

Saburo Onodera, Japan Air Lines, Tokyo, Japan and 

Kosuke Kamo, Sakurajima Volcanological Observatory, 

Kagoshima, Japan 

Japan Meteorological Agency (JMA) continuously 

watches 19 of 83 active volcanoes in Japan by means of 

monitoring volcanic clouds, seismic events, tilt changes, 

and other field observations. The information on 

volcanic activities that could affect safe operations of 

aircraft is issued by and based on JMA criteria, while 

satisfying that of ICAO SIGMET. The air-traffic control 

authority and the operators take their own 

countermeasures to prevent the volcanic-ash hazards. 

The following incidents by volcanic ash have been 

reported from the respective volcanoes in Japan s!nce 

1973; nine incidents for Sakurajima, four at Izu-Oostma, 

three for Usu and one for Asama. 

Kagoshima Airport is located 25 km north of 

Sakurajima volcano which has been at unrest in the 

explosive activity for 35 years. Planning has been 

carried out to establish an aviation safety system for the 

ash clouds. This project is divided in two stages. The 

first one is to detect the volcanic explosions using the 

data of explosion-quakes and air-shocks and the second 

one to simulate the diffusion of ash clouds with the data 

of the meteorological condition above the volcano. The 

simulation will be started automatically after detecting 

and determining that an explosion occurred. The first 

stage of the plan is completed and operating. The 

second stage is under planning 

GRAIN IMPACTS ON AN AIRCRAFT 

WINDSCREEN: THE REDOUBT 747 

ENCOUNTER 

David Pieri, Jet Propulsion Laboratory, Pasadena, CA and 

Robert Oeding, PDA Engineering, Costa Mesa, CA 

In December 1989, a Boeing 7 47-400 · aircraft 

intercepted an ash cloud from an eruption of the 

Redoubt Volcano. The encounter caused strong 

abrasion on leading edges and windscreens, and 

severely impaired engine function. To better 

understand the nature of the ash cloud, its remotesensing signature, and the encounter itself, we have 

obtained an abraded 150 kg polycarbonate-laminate 

front windscreen of the 747, to analyze quantitative 

characterizations of the impact pits, in terms of the sizeVolcanic Ash and Aviation Safety 35 
frequency distribution, areal density, and orientation. 

Ultimately, we would like to relate the impact signature 

to in-situ ash-cloud volume densities, and thus to its 

appearance in orbital imaging. In our analyses, we use 

(a) 7 47 slip-stream and boundary-layer characteristics, 

and (b) polycarbonate-laminate blanks, abraded by 

Redoubt ash at selected mass-flux rates in the laboratory 

for count calibrations. 

Inspection of the windscreen shows the following: 

(a) Strong abrasion zonation dependent on azimuth 

from the direction of flight, ranging from complete 

destruction (opaque frosting) of juvenile windscreen 

material near the centerline (15% of windscreen area), to 

the onset of inter-pit juvenile material at about 45 

degrees from the centerline, to only occasional elongated 

pits on the surface parallel to the direction of airflow 

(opaque frosting occurred within the inferred forward 

pilot line-of-sight); (b) Strong shadowing effects due to 

the presence of obstacles in the slipstream path--washer 

pylons and wiper blades appear to have interrupted the 

impact trajectory enough to have shielded small areas, 

even in the zone of head-on impact, suggesting 

mitigation of frosting by appropriate baffling upward of 

the area to be protected. This work was partially carried 

out under the NASA Solid Earth Sciences Program at the 

Jet Propulsion Laboratory, California Institute of 

Technology. 

DETECTION AND DISCRIMINATION OF 

VOLCANIC-ASH CLOUDS BY INFRA-RED 

RADIOMETRY I: THEORY 

A. J. Prata and I. J. Barton, CSIRO, Aspendale, Australia 

Volcanic-ash clouds with a high concentration of 

silicate particles exhibit optical properties in the infrared (8-13 J..Lm) that can be used to discriminate them from 

normal water /ice clouds. In principle, a simple 

radiometer equipped with at least two channels with 

appropriate passbands may be used to identify volcanic 

clouds. In this paper, we lay down the theoretical basis 

for such a radiometer. We solve the radiative-transfer 

problem in a cloudy atmosphere by using a discreteordinates model and present results for a variety of 

viewing conditions. These include vertical viewing 

downwards (from a satellite), horizontal viewing (from 

an aircraft) and vertical viewing upwards (from the 

ground). We also present some LOWTRAN-7 

calculations for representative atmospheres that include 

height variation of temperature, cloudiness, water vapor 

and other trace gases. 

36 Volcanic Ash and Aviation Safety 

Finally, we present results showing the effect of 

particle size and shape on the radiative transfer in an 

idealized volcanic cloud. 

VOLCANIC-ASH CLOUD WARNINGS IN THE 

AUSTRALIAN REGION 

Rodney J. Potts and Frank Whitby, Bureau of Meteorology, 

Melbourne, Australia 

As part of its routine operations the Bureau of 

Meteorology provides warnings to the aviation industry 

for volcanic-ash clouds over the Australian region and 

the region to the near north. This service has been an 

important component of Bureau operations since its 

introduction in 1982 when several aircraft suffered 

engine failure after encounters with volcanic-ash clouds 

over Indonesia. 

The warnings issued by the Bureau are based on 

notification of a volcanic eruption from the relevant 

neighbouring country, aircraft reports and unambiguous 

evidence on hourly Japanese Geostationary 

Meteorological Satellite images. 

There are inherent difficulties with the provision of 

this service as the discrimination of volcanic-ash clouds 

from water/ice clouds on present GMS satellite imagery 

is difficult and the ability to assess the dispersion and 

residence times of a volcanic-ash cloud is limited. 

The feasibility of using A VHRR Channel 4 and 5 data 

from the NOAA polar-orbiting satellites to discriminate 

volcanic-ash clouds from water I ice clouds has been 

previously demonstrated. The Bureau is in the process 

of installing an A VHRR antenna at Darwin and this 

antenna will enable good satellite coverage over the 

region north of Australia. The operational benefits 

provided by A VHRR data for the detection of volcanicash clouds is to be evaluated. 

Numerical models enable a forecast trajectory for the 

volcanic-ash cloud to be determined and this is to be 

developed using models run py the Bureau. 

IMPACT OF VOLCANIC ASH FROM REDOUBT 

VOCANO ERUPTION ON GE CF6-80C2 

TURBOFAN ENGINES 

Z. J. Przedpelski, General Electric Aircraft Engines, 

Evendale, OH, and T. J. Casadevall, U.S. Geological Survey, 

Denver, CO 

The 1989-1990 eruption of Redoubt Volcano, Alaska, 

and the near tragedy of KLM Flight 867 on 15 December 
1989 underscore the threat to aircraft safety from 

volcanic ash clouds. 

Between December 1989 and February 1990, at least 4 

commercial jet liners suffered damage from encounters 

with ash clouds from Redoubt Volcano. The most 

serious incident occurred on 15 December 1989 when a 

new Boeing 747-400 aircraft equipped with GE CF6-80C2 

engines encountered an ash cloud as the aircraft 

descended from the north for a scheduled landing in 

Anchorage. An eruption of Redoubt at 10:15 am (AST) 

produced an ash-rich eruption column which climbed to 

approximately 40,000 feet altitude. Wind speeds at the 

time were 100 knots in a northeasterly direction. At 

approximately 11:46 am (AST), KLM Flight 867 entered 

the volcanic ash cloud at approximately 25,000 feet 

altitude, 150 nautical miles northeast of Redoubt. 

Immediately upon entry into the cloud, the aircrew 

increased power and attempted to climb out of the ash 

cloud, gaining nearly 3,000 feet additional altitude 

before all 4 engines stalled. The aircraft descended 

approximately 13,000 feet during the next 8 minutes 

before the pilots restarted the four engines and resumed 

flight to Anchorage. While there were no injuries to 

passengers, the damage to engines, avionics, and aircraft 

structure from this encounter was significant. Similar 

engine thrust loss and engine and aircraft damage was 

experienced by two Boeing 747 aircraft during 1982 

volcanic eruptions of Galunggung Volcano in Indonesia. 

Other encounters between jet aircraft and ash clouds 

from Mount Redoubt on 15 and 16 December 1989 and 

21 February 1990 did not result in engine thrust loss. 

The primary cause of engine thrust loss in the 

volcanic ash ingestion events in Indonesia in 1982 and at 

Redoubt was the accumulation of melted and 

resolidified ash on the stage 1 turbine nozzle guide 

vanes. These deposits reduced the effective flow area 

causing an increase in the compressor operating line and 

compressor surge. Compressor airfoil erosion 

contributed to the loss of surge margin. Turbofan 

engines tested operating at high combustor discharge 

temperatures, and exposed to high concentrations of 

sand/ dust with low melting point, exhibit symptoms 

and conditions similar to those of engines exposed to 

volcanic ash. Operation at low-thrust level while in an 

ash cloud significantly reduces the rate of engine 

performance degradation. 

RADAR REMOTE SENSING OF 

VOLCANIC-ASH CLOUDS 

William I. Rose and Alexander B. Kostinski, Michigan 

Technological University, Houghton, MI 

Ground-based airport radar systems designed many 

years ago for meteorological purposes have been have 

demonstrated capable of tracking volcanic-ash clouds 

(Harris, et al., 1981, U.S. Geological Survey Professional 

Paper 1250, 323-333; Harris and Rose, 1983, ]. Geophys. 

Res., 88: 10969-10983). Among the useful information 

that results from their use is the duration of eruption, 

particle concentrations in ash clouds, the total mass of 

erupted materials, magma eruption rate, potential 

ashfall mass, ashfalllocations and times, durations and 

amounts of ashfall. 

The reflectivity factors for very dense ash clouds (3-

10 g/m3) on meteorological radar systems are several 

orders of magnitude less than for severe storm clouds 

that those radar systems are designed to detect. We 

estimated the ash concentrations likely to have been 

present in ash clouds encountered by aircraft based on 

our knowledge of eruption rates and plume dispersion 

models. These data suggest that volcanic clouds, much 

less dense than meteorological radar stystems are 

designed to detect (<0.2 g/m--:3), are a severe hazard to 

aircraft. Could a ground-based radar provide data for 

mitigation of ash cloud aircraft hazard? 

One effective approach to using radar as an 

instrument for ash cloud tracking of Alaskan eruptions, 

would be to place a ground-based system on the Kenai 

Peninsula, which is between Anchorage and the several 

historically active nearby volcanoes. A system that 

could map thin ash clouds (0.1 g/m3) with small (<10 

Jlm) particles over a long range (up to 500 km) would be 

most useful. Power generation is more expensive for 

long range radar systems with wavelengths less than 3 

em, but the trade off between better sensitivity and more 

expensive power at shorter wavelengths will be 

discussed. One consideration is that reposes between 

eruptions are long and eruptive events are rather shortlived. Besides its utility as a cloud tracking instrument, 

the radar would provide data that would help solve 

many unknown scientific problems concerning volcanicash clouds and ash transport. The incorporation of 

meteorological Doppler radar in order to measure 

Doppler shifts of ash clouds would be a useful addition 

for cloud track forecasting, because it could detect ash 

fallout and determine the particle size distributions 

within the clouds. A method might be devised for 

distinguishing volcanic and meteorological clouds using 

the doppler spectral width. Also, polarization diversity 

Volcanic Ash and Aviation Safety 37 
can provide additional information about ash particles 

and fallout mechanisms. 

REGIONAL MONITORING OF VOLCANIC 

ASH CLOUDS BY GEOSTATIONARY 

METEOROLOGICAL SATELLITE 

Yosihiro Sawada, Shizuoka Meteorological Obseroatory, 

Japan 

Visible and infrared images from GMS 

(Geostationary Meteorological Satellite) have 

successfully detected widely dispersed ash douds 

caused by big volcanic explosions, 1981 Alaid, 1981 

Pagan, 1982 Galunggung, 1982 Soputan, 1983 Una Una, 

1984 Mayon, 1984 Soputan, 1986 Chikurachki, 1986 IzuOshima, 1988 Kie Best, 1988 Banda Api and 1990 Kelut. 

GMS's detection rate of ash douds was about 14%. 

Limitation of the ground resolution and difficulty of 

discrimination of ash cloud from ambient atmospheric 

douds with GMS's detector prevent the further 

improvement of its detection rate, but it is possible to 

monitor ash clouds caused by big explosions which 

threaten aviation safety. Height of the ash cloud's top 

can be estimated from the coldest temperature on the 

surface of the ash cloud and the profile of air 

temperature around the volcano, and the intensity of the 

explosion can be evaluated with thermal energy release 

estimated from image data analyses. However, there are 

still unsolved differences between estimated and 

observed top heights of ash clouds, and some examples 

that may show active thermal discharge on the 

ascending ash cloud's surface. 

UTILITY OF A VHRR SENSOR FOR REMOTE 

SENSING OF ALASKAN ERUPTION CLOUDS 

D. J. Schneider and W.l. Rose, Michigan Technological 

University, Houghton, Ml 

The 1989-90 eruption of Redoubt Volcano and the 

1986 eruption of Augustine Volcano have provided an 

opportunity to test and refine the use of the advanced 

very high resolution radiometer (A VHRR), a 

multispectral sensor which is aboard two polar-orbiting 

NOAA weather satellites. Each satellite furnishes twice 

daily coverage of Alaska at a spatial resolution of 1.1 km, 

allowing a synoptic view of volcanic eruption clouds. A 

comprehensive collection of seventy images, 

representing a wide variety of eruptive and 

environmental conditions, have been studied during 

38 Volcanic Ash and Aviation Safety 

these two recent eruptive events. Seismic monitoring, 

direct observations of eruptions, ash-fallout information, 

radiosonde measurements, and ground weather 

observations provide ground truth, which helps us 

evaluate the satellite data. In addition, our work has 

included spectral reflectance studies of ash samples in 

the laboratory. 

At the date of writing, study of the Augustine images 

is completed (Holasek and Rose, Bull. Volcanol., in 

press), while the more extensive Redoubt images are still 

being intensely studied. Highlights of the conclusions so 

far: (1) Volcanic eruption clouds are detectable in a 

variety of weather conditions, both night and day, and 

over land or water. (2) The multiple infrared channels of 

the AVHRR sensor are essential in algorithms used for 

the discrimination of eruption clouds. (3) A single 

algorithm that can detect all eruption clouds has not 

been developed. Potential uses of the satellite data 

include monitoring and tracking eruption douds, as well 

as contouring particle burden within the douds. 

A MESOSCALE DATA ASSIMILATION 

SYSTEM ADAPTED FOR TRAJECTORY 

CALCULATIONS OVER ALASKA 

Thomas W. Schlatter and Stanley G. Benjamin, NOAA 

Forecast Systems Laboratory, Boulder, CO 

Soon after a volcanic eruption, it is relatively easy to 

locate the plume from satellite imagery, at least if the sky 

is clear. Later, however, as the plume disperses and 

thins, remote detection becomes more difficult. A series 

of analyses, feeding wind data to a trajectory model at 

frequent intervals, is one answer to the need for accurate 

tracking of the plume. 

NOAA's Forecast Systems Laboratory has developed 

a Mesoscale Analysis and Prediction System (MAPS) for 

assimilating surface and tropospheric data over the 

contiguous United States every three hours. Designed to 

serve aviation and local nowcasting, MAPS is scheduled 

for implementation at the National Meteorological 

Center (NMC) within one year. It relies heavily on 

automated aircraft reports available by the hundreds 

every hour. It uses isentropic coordinates in the free 

atmosphere and terrain-following coordinates near the 

ground. Isentropic coordinates are well-suited for 

trajectory calculations because air remains on these 

surfaces in adiabatic flow. 

MAPS has been adapted for use over Alaska. The 

previous definition of topography has been modified to 

allow for rougher terrain. A major obstacle must be 

overcome before the full potential of MAPS can be 
realized: automated aircraft reports over all of Alaska 

must be collected in real time so that the tropospheric 

and lower stratospheric wind field can be adequately 

defined every few hours. 

MASS, DISTRIBUTION, GRAIN SIZE, AND 

ORIGIN OF 1989-1990 TEPHRA-FALL 

DEPOSITS OF REDOUBT VOLCANO, ALASKA 

William E. Scott, U.S. Geological Survey, Vancouver, WA, 

and Robert G. McGimsey, U.S. Geological Survey, 

Anchorage, AK 

Twenty-one significant tephra falls occurred at 

Redoubt Volcano between 14 December 1989 and 26 

April 1990. Although modest in size compared to such 

recent eruptions at Mount St. Helens 1980 and 

Galunggung 1982, these events inferfered with and 

imperiled air travel and disrupted life and commerce in 

south-central Alaska. Tephra plumes rose to estimated 

altitudes of 7 to more than 12 km; most drifted to the 

northeast, east, or southeast. Individual tephra-fall 

deposits extend maximum distances of 50 to more than 

600 km from the volcano with mass concentrations 

ranging from 1 g/m2 to 1.5 X to5 g/m2. Mass estimates 

of individual deposits range from 6 X 107 to 4 X tolO kg 

summing to a total dense-rock volume of about 4 X 

107m3. 

The tephra fall of 15 December produced pumiceand crystal-rich deposits that were coarse grained near 

the volcano, whereas all subsequent events produced 

mostly ash-size deposits of lithic fragments and crystals 

(plagioclase, hornblende, pyroxene, and Fe-Ti oxides). 

Of the 19 events that produced lithic-crystal tephras, 17 

involved at least partial dome destruction. This 

association, coupled with visual evidence from 4 events 

and lack of large ballistic fragments near the vent, 

suggests that much of the lithic-crystal tephra originated 

in ash clouds elutriated from pyroclastic flows formed 

by dome collapse. 

Most 1989-1990 Redoubt tephra deposits other than 

proximal deposits of mid-December are composed of 

ash size material with mean grain sizes between 30 and 

125 microns. Beyond 20 km from the volcano, little 

material is coarser than 500 microns; sorting is poor to 

very poor. Mean grain size decreases and sorting 

improves with transport distance. Grain size of many 

samples is polymodal; modes common to numerous 

samples occur at 63-125, 16-32, 8-16, and 500-1000 

microns. These modes may be controlled by initial 

crystal-size distribution in the andesite of the dome. 

December 15, 1989 o Fairbanks 

Tephra deposit .,.-

640 .---- lsomass in gjm2 /71°~ I / ' Sample/observation site _ _ oc Delta fct / 

oHea(v / " /// / ;// # Toke 

// ... '"'/ 0 ~/ • • ,>::1""' I o 

I /} o 

I ~/;} . 

o Glennallen 

\ 

\ 

~\\§ "' ., ?{\~ 

\ 

\ 

150 \ 

.___c___.____, \ KILOMETERS 

~; ~ V Anchorage 

Redoubt ,;. o 

Volcano ~ c Soldatna ];,~ 

5 0/(A .$" ~f5 ~~ Gulf 

"'~ 

,_, 

of Alaska 

Volcanic ash deposits from the December 15, 1989 eruption of Mount 

Redoubt were detectable for more than 300 miles northeast of the volcano. The 

axis of the deposits passed through the town of Talkeetna. Methods used to 

construct this map are described in the paper by W. Scott and W. McGimsey 

(this volume). The star (''') indicates the position of the Boeing 747-400 

airplane of KLM flight 867, enroute from Fairbanks to Anchorage, when it 

encountered the ash cloud. Map courtesy of William E. Scott. 

Volcanic Ash and Aviation Safety 39 
ASH CLOUDS: CONDITIONS IN THE 

ERUPTION COLUMN 

Stephen Self and George P. L. Walker, University of 

Hawaii at Manoa, Honolulu, HI 

An eruption column is defined as the vertical or subvertical part of the emissions issuing from an explosive 

volcanic vent. Eruption columns range from very low, 

small-scale bursts to huge convective systems that 

rapidly transport ash, volcanic gases, and entrained air 

into the stratosphere. They have a lower gas-thrust part 

(the jet of material leaving the vent), that commonly 

represents less than 10% of the total height, and a 

convective thrust zone that constitutes most of the 

column but may be small in the Hawaiian-Strombolian 

types. Above this is the umbrella region, a zone of 

momentum-driven rise with considerable lateral 

spreading. Characteristics of eruption columns vary 

according to the style of explosive eruption, as 

summarized in the table below; rise rates shown are for 

the convective thrust region. 

Characteristics of Volcanic Eruption Columns 

GLOBAL FREQUENCY 

CHARAC- PER YEAR 

ERISTIC IS-10 1-2 >10 p.1- 1 <0.1 

Max. ht/width ~6-33/ 7-13 ~6-39/ 13-20 32-62/ 20-32 ~9-148/ 32- 65-130?/262-

thou.'s offt) ~60 490 

Avg. rise rate 15-35 15-35 50-260 ~5-33 260-650 ftls) 

Duration (h); 10-1000's; 10-1000's; 5-100's; < 1-200; semi- rl a few to 

f:ontinuity ntermittent to ntermittent to extremely continuous to rl100; semisemi- ~mi- spasmodic to continuous pontinuous to 

continuous ontinuous semi- f:ontinuous 

!continuous 

~sh content :.Ow- moderate High Moderate-high Moderate-high aigh 

Plher features "Dry" volatile- Wet, steam- IVery common; Coarse and ~ ery high rise 

bearing aden columns; ~idely variable fine particles in rates; large 

column; few much ~tyle of lligh column; magnitude; 

me particles; aggregation of ~ctivity; !often short- nfrequent 

!maY be diffi- ash IISsociated w/ ived but 

f:ult to detect small ash-flow! ~intained 

!visually 

Recent ~lauea,1983- ~ite Island, Redoubt, aekla, 1991; mall: Mount examples ~6; Pacaya, 1976-82; 1989-90; ~ountSt. St. Helens, 

1990; Oshima, IUkinrek, 1977; Sakura-jima ~elens, 1980 May 1980; 

1986 ~urtsey, 1965 continuous) big: Katmai, 

1912 

Type aawaiian/ ~urtseyan Vulcanian ~ub-ptinian- Ash flow (co-

~trombotian ~hreato- !Plinian gnimbrite) 

~gmatic) 

40 Volcanic Ash and Aviation Safety 

VOLCANOES: THEIR OCCURRENCE AND 

GEOGRAPHY 

Tom Simkin, Smithsonian Institution, Washington, DC 

The explosive volcanoes that threaten air safety tend 

to be in long, linear belts near continental margins. They 

cover less than 0.6% of the earth's surface. At least 1,200 

volcanoes have erupted in the last 10,000 years and thus, 

since the lifetimes of most volcanoes are very long, are 

likely to erupt again in the future. Of these, however, 

only about 60 are active in a typical year, and that 

activity may range from the mild pyrotechnics of Italy's 

Stromboli to prehistoric catastrophes that dwarf recent 

eruptions such as Mount St. Helens 1980 or Krakatau 

1883. As with earthquakes, the bigger eruptions happen 

less often than the smaller, with St. Helens-sized events 

perhaps once a decade and events like Redoubt 1989 and 

Ruiz 1985 two or three times a year. During the years 

1975-1985 we found that over 100 eruptions penetrated 

the altitude range of air traffic, and at least 9 passed into 

the stratosphere where volcanic products are easily 

dispersed around the world. 

Eruption durations were often not recorded 

historically, but they are known to range from minutes 

to thousands of years. The median duration is 2 months 

and few eruptions last longer than 3 years. Pulses of 

activity mark all but the shortest eruptions, and the 

paroxysmal event may come at any time from the first 

day (ca 45%) to months or even years after the start. Of 

particular importance for volcano hazards is the fact that 

unusually violent eruptions commonly occur after 

unusually long periods of repose. The historic record in 

many parts of the world is far shorter than the hundreds 

or thousands of quiet years that precede violent 

eruptions, meaning that some of our most dangerous 

volcanoes may be those not currently recognized as 

active. Of the 14 largest explosive eruptions in the 19th 

and 20th centuries, all but 3 were the first historic 

eruption known from the volcano. These factors 

emphasize the importance of communicating reports of 

new eruptions. We at the Smithsonian hope for more 

news from "eyes in the sky," and will do our best to 

disseminate volcano reports as we've been doing for 

nearly a quarter century (see McClelland abstract, this 

volume) 
USE OF SATELLITE IMAGERY TO TRACK 

VOLCANIC ASH CLOUDS IN INDONESIA: A 

NEW POSSIBILITY FOR AVIATION SAFETY 

Tumpal Situmorang, and Subroto Modjo, Volcanological 

Suroey of Indonesia, Bandung, Indonesia 

The Indonesian archipelago, which has 129 active 

volcanoes and is inhabited by 180 million people, has a 

high volume of air traffic. Most airline service between 

Asia and Australia must pass either through its principal 

air-traffic centers located near major volcanoes (Jakarta, 

Medan, Denpasar, Manado) or along air routes in 

Indonesian airspace. There were more than 100 

explosive volcanic eruptions from 22 volcanoes during 

the last ten years (1980-1990). On the average, one major 

explosive eruption sends volcanic ash into the 

stratosphere and about ten less powerful eruptions 

occur every two years. The eruption products could 

threaten people directly in the hazardous zone, as well 

as having worldwide impact (e.g.: aviation disturbance, 

air pollution, unusual weather). 

The remote sensing tools available include air 

photographs, radar images, earth-observing satellites 

images, thermal infrared images, and environmental 

satellite images. These offer new possibilities in surveys 

at various scales. In Indonesia, some of the satellite 

images (Landsat, GOES/NOAA, GMS) are received and 

distributed by LAP AN (the Indonesian Institute of 

Aeronautics and Space) Ground Station in Pekayon near 

Jakarta. 

The volcanological science has benefited from use of 

remote sensing techniques. For tracking ash clouds, the 

very high temporal resolution images of environment 

satellites (GOES/NOAA, GMS) is most effective. Rapid 

acquisition and analysis of images allows us to issue an 

early warning for aviation safety and to the population 

living in the area that might be affected by ash fall. 

Images acquired by the GMS from a few hours to several 

days after the violent eruption of Kelut Volcano (East 

Java) on February 10, 1990, and Landsat images of East 

Java (covers Kelut, Semeru, Arjuno-Welirang, 

Lamongan volcanoes) taken on September 12,1989, have 

been analyzed. Results are presented in this paper. 

PREPARATION AND DISSEMINATION OF 

VOLCANIC ASH PLUME INFORMATION BY 

THE MONITORING AND AVIATION BRANCH 

OF THE NATIONAL METEOROLOGICAL 

CENTER 

Arthur H: Smith, National Meteorological Center, 

Camp Springs, MD 

Ash clouds produced by volcanic eruptions have a 

significant impact on aviation operations. This has 

resulted in the formulation of a multi-agency system to 

provide current and forecast information regarding the 

location, extent, and projected movement of the ash 

cloud to the aviation community. The Monitoring and 

Aviation Branch (MAB) of the National Meteorological 

Center (NMC) plays an important role in this support to 

the aviation community. 

The functions of MAB include initiating the volcano 

response plan. This would be done by notifying the 

NESDIS Synoptic Analysis Branch when MAB receives 

information of a volcanic eruption from a Pilot Report or 

possibly a call from the Central Flow Weather Service 

Unit (CFWSU). 

A second eruption-related function of the MAB is the 

preparation of high-level significant weather prognostic 

charts that depict the predicted volcanic ash plume or 

contain the disclaimer "Potential Volcanic Ash, See Local 

SIGMETS." The depiction of the plume on the 

prognostic chart is limited to those volcanic eruptions 

that are long-term and continuous. 

The role of MAB's CFWSU in collecting volcanic ash 

plume observations and disseminating volcanic ash 

plume forecasts from and to the aviation community 

will be presented. The preparation, content, and 

dissemination of volcanic SIGMETS by MAB will be 

discussed. 

MAB also has the capability to generate computerprepared volcanic ash trajectory forecasts. These 

forecasts are used by MAB meteorologists in the 

preparation and issuance of volcanic SIGMETS and 

high-level volcanic ash plume forecasts. The method 

used to prepare the trajectories will be briefly discussed 

and examples of the trajectory forecasts shown. 

Volcanic Ash and Aviation Safety 41 
VOLCANIC ASH DETECTION AND 

TRACKING SYSTEM APPLIED TO 

INDONESIA: A PROPOSED ALTERNATIVE 

Indroyono Soesilo, Agency for the Assessment and 

Application of Technology (BPPT), Jakarta, Indonesia 

A 10-month continuous series of volcanic eruptions 

of ~t. Galunggung, i.n West Java, Indonesia, during the 

penod of ~982-83 disrupted the Singapore-Sidney air 

r~u~e corndor .~d forced jumbo jets of Singapore 

Auhnes and Bntish Airways to make safe emergency 

landings in Jakarta. No accident occurred; however, a 

real time information system network needs to be 

improved to cover this volcanically active 1700-island 

nation stretching 5100 km across the equator. 

A computerized Indonesian Volcanic Hazard 

Information System (IVHIS) database should initially be 

developed, with the inclusion of geographic locations of 

129 Indonesian active volcanoes and coastlines, islands, 

lakes, rivers, and administrative boundaries. 

Infrastructure digitized data (roads, cities, railroads, 

airports, etc.) would complement the database . 

. Volc~nic ash detection and tracking activities are 

being Simulated by the inclusion of real-time satellite 

and telemetric data into the IVHIS database within a 

designated period of time. Through a domestic 

tel~ommunication satellite network system, data are 

being shared by targeted agencies. 

DISPERSAL OF ASH BY VOLCANIC 

ERUPTION COLUMNS 

R. S. J. Sparks, J. S. Gilbert, Bristol University, United 

Kingdom, M. I. Bursik, Jet Propulsion Laboratory, Pasadena, 

CA, and S. N. Carey, University of Rhode Island, 

Kingston, RI 

Vol~anic eruption columns consist of a rapidly 

ascending buoyant plume and a laterally expanding 

upper umbrella region. Concentration of volcanic ash is 

postulated to decrease exponentially with time in the 

turbulent column. For the umbrella region, the 

concentration of ash, C, decreases with distance from the 

vent, r, in a Gaussian fashion 

C/C0 = exp [-r2-r12) v/Q] 

where C0 is the initial concentration, v is the terminal 

~ttling velocity of the particle, r1 is the horizontal 

distance from the vent to the umbrella margin and Q is 

th~ flow rate. Q is determined by eruption column 

hetght and consequentially by discharge rate of magma. 

This simple theory shows good agreement with 

42 Volcanic Ash and Aviation Safety 

laboratory experiments on sedimentation from plumes 

and with field data from the Fogo A plinian deposit (Sao 

Miguel, Azores). The theory is valid for powerful 

eruptions with relatively weak wind. For the Fogo A 

eruption the theory has been tested down to 1/2 mm 

diameter. In a strong wind the same principles imply an 

exponential decrease of concentration with distance 

C/C0 = exp [-dv /wh] 

where w is the wind speed, d is the downwind distance, 

and his the depth of the wind-transported plume layer. 

This result has not been validated in experiments, but is 

consistent with the overall exponential thickness 

decrease observed in most pyroclastic fall deposits. The 

model can be used to calculate particle concentration 

(mg/m3) in plumes as a function of distance from 

source if assumptions are made about the initial particle 

grain size distribution and column height. Processes of 

atmospheric diffusion and particle aggregation will, 

however, modify concentration in downwind plumes in 

a manner that is not yet completely understood. 

APPLICATION OF RADAR FOR THE 

OBSERVATION OF VOLCANIC ASH 

Melvin L. Stone, Lincoln Laboratory, Lexington, MA 

Radar detection and tracking of volcanic ash from 

Mount St. Helens demonstrated the usefulness of real 

time surveillance o the clouds (Harris, and Rose, 1983, 

JGR, 88, C15, p. 10969-10983). The radars used were 

operational NWS magneton systems. The low radar 

reflectively reported for volcanic ash clouds make the 

detection and characterization of the potential threat to 

aviation a formidable task. Both the NWS and the FAA 

are procuring pulsed Doppler radars with enhanced 

sensitivity. Contemporary airborne weather radars also 

have an improved detection capability. An overview 

will be presented of radar principles and technical issues 

related to various options for observing volcanic ash. 

Among the parameters to be considered are the 

operating frequency, power-aperture product, azimuth 

and elevation resolution, Doppler measurement, and 

update rate. The performance capability of currently 

operational and planned radar systems will be 

described. Candidate dedicated systems for proximate 

and stand -off surveillance will be suggested. 

This work was supported by the Federal Aviation 

Administration. The Federal Government assumes no 

liability for its contents or use thereof. 
MODELING VOLCANIC ASH TRANSPORT , DISPERSION AND DEPOSITION 

Barbara J.B. Stunder, Air Resources Laboratory, Silver 

Springs, MD 

As required by a NOAA/FAA Memorandum of 

Understanding on Volcano Hazards Alerts, NOAA/ Air 

Resources Laboratory (ARL) makes volcano ash 

trajectory forecasts. The three components of the 

present ARL product are (1) trajectory maps, (2) tables of 

3-hour tr~jecto~ endpoints, and (3) written descriptions 

of the trajectones. It would be desirable for airline pilots 

to know more about the actual ash location with as 

much_ detail as possible. To expand the present product, 

ARL Is developing a model to simulate ash transport. 

Meteorological data from the NOAA/Forecast Systems 

Laboratory Mesoscale Analysis and Predication System 

(MAPS) provide initial conditions and short-term 

forecast data; larger scale and longer term 

meteorological data is from the NOAA/National 

Meteorological Center (NMC). Dispersion and wet and 

dry ~eposition are also included in the model. Output 

descnbes the ash cloud in both space and time. Details 

of the model are described and example output shown. 

CURRENTSTATEOFVOLCANO 

MONITORING: STRENGTHS AND 

WEAKNESSES 

D.A. Swanson, U.S. Geological Survey, University of 

Washington, Seattle, WA 

Perhaps 150 of Earth's 550 historically active 

volcan~es are monitored to some degree. The capability 

to ~omtor volcanoes and warn of impending eruptions 

has Improved over the years but has reached neither an 

acceptabl~ level of reliability nor an adequate 

geographic breadth to warrant satisfaction on the part of 

volcanologists. The most widely used and successful 

mo.ni_toring technique is the recording of earthquake 

activity from a volcano. Such seismic monitoring 

potentially provides real-time information on the state of 

a volcano, because data can be acquired and telemetered 

in~t~ntly from re~ote field sites to an observatory or 

cnsis center. An Increase in earthquake activity usually 

but not always precedes an eruption. Sophisticated 

procedu~es have been devised to analyze seismic 

Inf.ormation, but the single most crucial piece of 

evidence for warnings is simply the number of 

earth~uakes ~r u~it time. The newly developed ability 

to estimate seisrmc-energy release in real time is also 

very useful. The occurrence of false alarms (earthquake 

flurries with no eruption) is a significant weakness of 

seismic monitoring, so it is wise to augment that 

monitoring with other real-time methods to provide a 

more complete picture of the volcano. The two such 

methods most commonly used are geodetic monitoring 

and gas monitoring. Continuous geodetic monitoring is 

now effectively restricted to measurements of changing 

ground tilt with electronic tiltmeters, but in a few years 

Global Positioning System (GPS) instruments will 

become widely used for monitoring. Standard 

electronic-surveying techniques are often employed to 

detect swelling of the volcano, but they lack real-time 

capability. Geodetic monitoring, whether continuous or 

by repeated surveys, has proven useful at some 

volcanoes but is not a general panacea. Changes in 

Earth's gravity field can be monitored continuously but 

do not yet provide the basis for a dependable warning 

system. Real-time monitoring of volcanic gas 

composition and emission rate is conducted at a few 

volcanoes with mixed results, but this technique is 

evolving quickly and will become more useful. Thermal 

IR imaging is another technique whose promise has yet 

to be fulfilled. 

Volcanoes are such remarkably complex natural 

systems that warning of impending eruptions is difficult 

under the best of circumstances. Under the worst, as in 

areas for which monitoring is limited or absent (such as 

in the Aleutians), warning is generally impossible. 

Volcanology has far to go before either the timing and or 

the style of each significant eruption can be foretold; 

meanwhile, the public should be aware that both large 

and small eruptions can and will take place 

unannounced at volcanoes around the world. 

THERMAL PROPERTIES OF VOLCANIC ASH 

Samuel E. Swanson and James E. Beget, University of 

Alaska, Fairbanks, AK 

Melt quenched to a glass is a common phase in 

volcanic ash. The melt represents the most chemically 

evolved part of the magma with compositions typically 

10-20 wt. % higher in Si02 than the condensed lavas. 

For example, bulk compositions of lavas from the 1989-

90 eruption of Redoubt Volcano are high-silica andesites 

(Si02 =58 to 63 wt. %), while groundmass and tephra 

glasses are rhyolitic (Si02 = 69-78 wt. %). Other 

volcanoes near Redoubt show similar relations 

(Augustine: lavas 51 to 63 wt. % Si02, glass 75 to 78 wt. 

% Si02; Iliamna: lavas 51 to 61 wt. % Si~, glass 79 wt. 

Volcanic Ash and Aviation Safety 43 
% Si02; Spurr: lavas 54 to 63 wt. % Si~, glass 59 to 73 

wt.% Si~). 

The rhyolitic melts plot close to the pressure 

minimum in the system NaA1Si308-KA1Si308-Si02. 

Liquidus temperatures (1 bar, dry) of these glasses are 

about 96QOC. Operating temperatures of commercial jet 

engines (600-700°C) are below the melting temperatures 

of these rhyolitic glasses, but above the glass 

transformation temperature (Tg, about 630°C) of the 

rhyolitic glasses. Above the Tg, "glass" behaves as a 

supercooled liquid and has considerable translational 

mobility. When ingested into an operating jet engine, 

glass particles will be heated, soften, and adhere to the 

engine parts. Annealing of the particles and flow of the 

glass will produce a glassy coating, thus creating 

operational problems for the jet engine. 

PERFORMANCE DETERIORATION ON 

AIRCRAFT JET ENGINES WITH PRESENCE OF 

SOLID PARTICLES 

W. Tabakoff, University of Cincinnati, Cincinnati, OH 

Commercial and military airplanes are often exposed 

to foreign objects such as birds, hailstones, ice slabs, 

runway gravel, and others which are ingested into 

engine inlets. The ingestion of particulate matter such as 

sand and dust leads to the deterioration of these engines 

both structurally and aerodynamically. Some of the 

mechanisms that cause foreign-object ingestion are: (a) 

the vortex from engine inlet to ground during high 

power setting, with the aircraft standing or moving on 

the runway, (b) sand storms transporting sand to several 

thousand feet altitude, (c) thrust reverser efflux at low 

airplane speed may blow sand, ice and other particles 

into the engine inlets, (d) the most dangerous 

environment for jet engines is particulated clouds from 

the eruption of volcanoes. This paper will present the 

methods and results of several theoretical and 

experimental investigations concerning the effect of the 

presence of solid particles on the performance of 

turbo machines. 

DEVELOPMENT OF A PREDICTION SCHEME 

FOR THE VOLCANIC ASH FALL FROM 

REDOUBT VOLCANO 

H. L. Tanaka, University of Alaska, Fairbanks, AK 

A volcanic plume prediction model has been 

developed for Alaska volcanoes including Redoubt 

44 Volcanic Ash and Aviation Safety 

Volcano. This is a 3-dimensional Lagrangian-diffusion 

model with gravity fallout of volcanic plume particles. 

The near real-time and forecasted upper-air data are 

provided by the NMC global model product through the 

Unidata program. 

The model has been tested with Redoubt Volcano 

eruption records and compared with the NOAA 

A VHRR satellite data analyses. The 3-dimensional 

distributions of the plume dispersal are displayed on the 

computer screen as functions of time after the eruption. 

The simulation results agree reasonably well with the 

A VHRR satellite data analyses. 

The model predictions have been demonstrated 

routinely at the Alaska Volcano Observatory (AVO) for 

daily hypothetical eruptions. These demonstrations 

show that the model is capable, within 6 minutes after 

any eruption report, to display traveling plume locations 

and dispersal for the following several hours. The 

prediction will be especially useful during dense-cloud 

situations when the visual monitoring is difficult, a 

common condition in winter at the Gulf of Alaska. 

The model products are immediately available for 

aviation purposes through computer networking and 

FAX transmission supervised by the AVO. Because the 

model is operational at the AVO, it can offer the timely 

predictions important to aviation and public safety. 

VOLCANO OBSERVATORIES AND 

VOLCANIC ASH WARNING 

R.I. Tilling, U.S. Geological Survey, World Organization of 

Volcano Observatories [WOVOJ, Menlo Park, CA, T. J. 

Casadevall, U.S. Geological Survey, Denver, CO, 

G. Heiken, Los Alamos National Laboratory, Los Alamos, 

NM, and G. E. Sigvaldason, University of Iceland 

[WOVO], Reykjavik, Iceland 

Incidents of aircraft encountering volcanic ash clouds 

have become more common in recent decades as air 

traffic has greatly increased worldwide. Airborne 

volcanic ash poses an infrequent but growing threat to 

aviation safety, particularly in the circum-Pacific region. 

Since 1986, the Volcanic Ash Warnings Study Group, 

under the aegis of the International Civil Aviation 

Organization (ICAO), has addressed the problem of ashaircraft encounters, resulting in some improvements in 

pilot education, information flow, and 

reporting/warning procedures (ICAO regulatory 

documents). Beginning in 1988, in cooperation with 

ICAO, the World Organization of Volcano Observatories 

(WOVO), a commission of the International Association 

of Volcanology and Chemistry of the Earth's Interior 
(lA VCEI), attempted to launch an International Airways 

Volcano Watch, a voluntary network established to 

improve communications between volcano 

observatories and other institutes that monitor 

volcanoes, meteorological offices, flight-control agencies, 

and pilots. Members of WOVO--about 40 institutions in 

19 countries--were requested to initiate meetings with 

the civil aviation and meteorological offices in their 

regions to develop contacts and procedures so that 

information, including warnings about volcanic 

eruptions, could be exchanged on a timely basis. In 

return, volcanologists would have greater opportunity 

for access to pilots' real-time observations of eruption 

phenomena otherwise reported. To date, only a few 

observatories have participated in Volcano Watch, and 

WOVO is working to encourage wider participation in 

this voluntary international endeavor. Nonetheless, 

promising progress has been made in Indonesia, Japan, 

New Zealand, Papua New Guinea, and the U.S.A. 

Successes achieved during the past decade indicate that 

volcanologists and volcano observatories can, and 

should, take a more active role to further mitigate the 

risks posed by volcanic ash-aircraft encounters in the 

1990s--designated the International Decade for Natural 

Disaster Reduction by the United Nations. 

CURRENT PROCEDURES FOR IN-FLIGHT 

ADVISORIES REGARDING VOLCANIC 

ERUPTIONS AND ASH IN DOMESTIC 

AIRSPACE 

Michael A. Tomlinson, NOAA-National Weather Service, 

Silver Spring, MD 

The National Weather Service has established 

policies and procedures for issuing In-flight Aviation 

Weather Advisories regarding conditions associated 

with volcanic eruptions. This was in response to user 

concerns regarding the potentially disastrous 

consequences of jet aircraft encounters with material 

from volcanic eruptions, and in coordination with 

international efforts to address the same issue. This 

paper discusses the procedures, the underlying policies, 

and the problems associated with using the Significant 

Meteorological (SIGMET) Advisory program for a 

nonmeteorological event. Current procedures recognize 

a user requirement for two basic types of information, 

notification that an eruption has occurred, and 

information regarding the location, extent, and 

movement of hazardous volcanic material. Current 

policy is to provide a one-time-only eruption advisory as 

·rapidly as possible, followed by a volcanic ash "hazard" 

advisory as soon as sufficient information is available. 

There are several problems associated with the latter 

product. The most urgent type of advisory message, a 

SIGMET, is the chosen vehicle for this information. 

Unfortunately, all of the other criteria for issuing a 

SIGMET are always hazardous while volcanic material is 

not. This creates a potential for "over warning" which 

negatively impacts aircraft operations and damages the 

credibility of the advisory program. There is also no 

known correlation between current airborne material 

detection capabilities and the extent of the actual hazard. 

Events such as the Mount St. Helens and Mount 

Redoubt eruptions have demonstrated the tremendous 

variability in volcanic events and in the hazards they 

create. Procedures to provide useful advisories in any 

eventuality are extremely difficult to develop. The 

existing procedures are detailed and their rationale 

explained. The prerequisites for improvements are also 

briefly discussed. 

THE AERONAUTICAL VOLCANIC ASH 

PROBLEM 

Jerald Uecker, NOAA-National Weather Service, Silver 

Spring, MD 

The International Civil Aviation Organization 

requires warnings and flight planning information about 

one of the most potentially hazardous but nonmeteorological aeronautical phenomena that exists, 

volcanic ash. This paper discusses the provision of 

required information based upon the experiences Mount 

St. Helens and Mount Redoubt in the United States. The 

frequency and duration of the eruptions as well as the 

lack of guidelines about ash concentrations affecting 

aircraft has made it difficult to meet the requirements for 

supporting both safe and efficient aeronautical 

operations with available information messages. The 

paper also reviews the requirements and current 

support in the U.S. and suggests improvements in 

meeting them. Meeting the aeronautical information 

requirements for this nonmeteorological phenomenon 

requires cooperative research and development among 

various disciplines to attain not only safe but also 

efficient operations. 

Volcanic Ash and Aviation Safety 45 
AIRCRAFT A VOIDANCE REGIONS FOR 

VOLCANIC ASH 

Peter L. Versteegen, Douglas D. D' Autrechy, Science 

Application International Corporation, Mclean, VA, and 

Charles Gallaway, Department of Defense, Alexandria, VA 

This paper describes a methodology for the 

prediction of a region that aircraft should avoid when 

the air contains dust from recent eruptions of volcanoes. 

The methodology consists of two parts, the dust model 

and the avoidance-area model. The dust model predicts 

the locations of ash particles from volcanic clouds. The 

avoidance-area model uses the predicted particle 

locations to determine an avoidance region of minimal 

areal extent. The methodology is PC based and can 

predict such avoidance regions in near real time. A 

model such as this could link a volcano observatory, a 

weather station, and an aircraft operation center 

The avoidance area model uses predicted particle 

locations to define a volume in space of minimal cross 

sectional area. This region contains all possible cloud 

particles at the time of interest. The avoidance region 

can be defined for a single altitude or a range of 

altitudes. 

The dust model includes key elements that affect the 

prediction of particle locations. Key elements include: 

the specification of cloud initial conditions and a three 

dimensional wind field; the transport and dispersion 

characteristics of the atmosphere; and the particle 

terminal fall velocities. The initial conditions of the 

cloud consist of a description of the cloud geometry, 

mass distribution, and particle size distribution. This 

initial cloud is represented by a number of horizontal 

wafers. Each wafer contains the mass and effective 

radius of each of the particle sizes. The location of 

representative particles are computed with a modified 

Euler method using a time dependent wind field. 

Dispersion is modelled by an empirical correlation. The 

fall rate of a particle is determined from its local terminal 

velocity, which is a function of size and altitude. 

Mount St. Helens ash deposition data have been used 

in a study to assess the adequacy of the model. 

Reasonable agreement was found between predictions 

and measurements. 

46 Volcanic Ash and Aviation Safety 

VOLCANIC ASH AS AN INGESTION HAZARD 

Alan T. Weaver, Pratt & Whitney, Hartford, CT 

This topic will illustrate the relative engine ingestion 

hazard of volcanic ash compared to other more common 

hazards such as birds, sand, tires, ice, and severe 

weather. The causes of other ingestions will be shown to 

relate to their occurrence rates. The relationship of the 

ingestion event itself to economic damage as well as the 

more important aspect of flight safety will be stressed. 

The relative effects of the ingestion on risk to safety of 

flight will be explained and put into perspective relative 

to occurrence rates of the ingestion event itself. Finally 

areas of minimization and/ or mitigation of operational 

impact will be discussed. 

NEW ROLES FOR AIRPORTS IN RESPONSE 

TO VOLCANIC DISTRIBUTION 

Anders Westman, Alaska International Airport, 

Anchorage, AK 

On December 15, 1989, Mount Redoubt, a volcano 

located on the Alaska Peninsula, experienced a major 

eruption. This event, and numerous subsequent events, 

had a dramatic disruptive impact on the civil air 

transportation system in Alaska, exacerbated by the fact 

that it occurred during one of the busiest travel periods 

of the year. Almost immediately, air carriers began 

cancelling flights, leaving passengers stranded and 

airport revenues greatly reduced. The Alaska 

International Airport System (AlAS), which owns and 

operates both Anchorage and Fairbanks International 

Airports, was faced with a crisis. 

The response of AlAS management to this crisis 

illustrates of the challenges facing airport management, 

and the possible pro-active steps that may be taken to 

mitigate the impact on the travelling public, the airlines, 

and ultimately to the revenue stream. The actions that 

may be selected by the airport can be divided into two 

groups: direct and indirect. It is important to point out 

that the airport, with respect to events of this nature, is 

not one of the central participants, those roles being held 

by the federal government and the air carriers. The 

direct actions primarily involve airfield and terminal 

management, and will not be discussed in depth. The 

indirect actions place the airport in a unique role; that of 

facilitator. This role will be discussed in depth. 
ASH-FALL DEPOSITS FROM LARGE-SCALE 

PHREATOMAGMATIC VOLCANISM: 

LIMITATIONS OF AVAILABLE ERUPTION 

COLUMN MODELS 

C. J. N. Wilson, University of Cambridge, Cambridge, UK 

Several models consider the structure and dynamics 

of eruption columns, and can be used to estimate the 

column height and discharge rate of prehistoric 

eruptions from the dispersal characteristics of their ashfall deposits. These models are very successful in 

characterising deposits from "dry" eruptions (i,e. where 

the explosive activity is driven solely by release of 

volatiles dissolved in the magma, typically <6 wt% 

H20). They also provide accurate and useful 

predictions of the size and growth rates of "dry" 

eruption ash clouds. 

However, some historical eruptions are known, and 

an increasing number of prehistoric deposits recognized 

to be from "wet," or phreatomagmatic, activity where 

external water (e.g. sea, lake, or groundwater) in various 

proportions (>10 wt%) interacted with the magma. The 

22,500 year old Oruanui eruption (New Zealand) is of 

this type, and several features of its greater than 500 km3 

ash-fall deposit suggest that available eruption-column 

models cannot be applied to large "wet" eruptions, 

where column dynamics are dominated by latent heat 

associated with evaporation or condensation of water. 

Existing eruption-column models imply that 

involvement of water will decrease column height and 

vigor, yet some fall units in the Oruanui deposit have 

such extremely wide dispersal that they plot beyond all 

known examples of "dry" fall deposits. This 

contradiction between implications of low column 

height (and vigor?) from existing models and 

improbably high columns implied from dispersal 

characteristics of the Oruanui ash-fall beds suggests that 

other factors such as unusually rapid expansion of, or 

significant internal turbulence within, the eruption ash 

clouds must be invoked. These factors have to be 

considered before accurate modelling can be made of 

"wet" eruption columns and assessment made of the 

resulting threats to aviation. 

EFFECTS OF VOLCANIC ASH ON AIRCRAFT 

POWERPLANTS AND AIRFRAMES 

Lester M. Zinser, NCAR Retired, Grand ]unction, Colorado 

This article is about the use of and the effects on 

aircraft used as a research platform to penetrate and 

sample volcanic eruptions. The article will discuss 

fouled plugs, oil sample analyses, and damage to the 

windscreen, airframe, and rotating equipment. The 

plane used for research was a Beechcraft Queen Air 

Model B-80 powered by two Lycoming IGS0-540 

reciprocating engines. Two trips were made to Central 

America to sample three active Guatemalan volcanos, 

one in February 1978, and again in February 1980. On 

March 26, 1980 Mount St. Helens became active, the 

aircraft was re-instrumented, and on April 2, 1980, 

ferried to Portland for research flights through Mount St. 

Helens' plumes. There was considerable information 

available about the contents of volcanic eruptions, but 

little was known how direct sampling would effect 

aircraft performance and materials. On February 10, 

1978, the volcano Fuego erupted, and the first direct 

flight through a dense volcanic cloud was accomplished. 

Thirty hours of flight time was logged during the 1978 

program with an estimated 3-5 hours of flight in various 

types of ejected volcanic material. In 1980, between the 

Central America and Mount St. Helens projects another 

forty to fifty hours was flown with an estimate of 4-5 

hours in volcanic-ash clouds of varying density. 

Volcanic Ash and Aviation Safety 47 
AUTHORS' ADDRESS LIST 

Mr. David M. Bailey 

Executive Manager 

Grant County Airport 

Terminal Building 

Moses Lake, W A 98837 

(509) 762-5363 

FAX: (509) 762-2713 

Mr. Jorge Barquero H. 

Observatorio Vulcanologico Y 

Sismologico De Costa Rica 

Universidad Nacional 

Apartado 86-3000, Heredia 

COSTA RICA 

374570- 377023- 376363, ext 2304, 2405 

FAX(506)380086 

Dr. Ian Barton 

CSIRO Division of Atmospheric Research 

Private Bag No. 1, Mordialloc 

Victoria 3195 

AUSTRALIA 

03-586-7668 

FAX: 03-586-7600 

Mr. Craig I. Bauer 

National Weather Service 

701 C Street, Box 23 

Anchorage, Alaska, 99513 

(907) 271-5107 

FAX: (907) 271-3711 

Mr. Gregory Hayhurst 

INC-7 MS J-514 

Los Alamos National Laboratory 

Los Alamos, NM 87545 

(505) 667-4534 

FAX: (505) 665-5688 

Dr. James E. Beget 

Department of Geology and Geophysics 

University of Alaska 

Fairbanks, AK 99775 

(907) 474-7565 

FAX: (907) 474-5163 

Mr. Stanley G. Benjamin 

NOAA Forecast Systems Laboratory 

NOAA/ERL/FSL R/E/FS1 

325 Broadway 

Boulder, CO 80303 

(303) 497-6938 

FAX: (303) 497-6750 

48 Authors' Address list 

Dr. Alain Bernard 

Geochimie/160, ULB 

50 Av. Roosevelt 

1050 Brussels 

BELGIUM 

FAX: 32-2-650-2872 

Dr. 0. A. Braitseva 

Institute of Volcanology 

Petropavlovsk-Kamchatsky, 

683006, USSR 

Dr. Gregory Bluth 

Earth Sciences Directorate 

NASA, Goddard Space Flight Center 

Greenbelt, MD 20771 

(301) 286-2754 

FAX: (301) 286-9200 

Mr. Steven R. Brantley 

U. S. Geological Survey 

5400 MacArthur Blvd. 

Vancouver, WA 98661 

(206) 696-7994 

FAX: (206) 696-7866 

Dr. Sutikno Bronto 

Volcanological Survey of Indonesia 

57 Jalan Diponegoro 

Ban dung 

INDONESIA 

62-22-72606 

FAX:62-22-75588 

Dr. Marcus I. Bursik 

MS 183-501 

Jet Propulsion Laboratory 

California Institute of Technology 

Pasadena, CA 91109 

(818) 354 7557 

FAX: (818) 354 0966 

Mr. Ernest E. Campbell 

Boeing Commercial Airplane Group 

P.O. Box 3707, M/S 2T -61 

Seattle, W A 98124-2207 

(206) 544-5203 

FAX: (206) 237-0352 
Dr. Guy Camus 

Universite Blaise Pascal & C.N.R.S. 

Unite de Recherche Associee n°10 

5 rue Kessler63038 Clermont-Ferrand Cedex 

FRANCE 

73.40.63.63 

FAX: 73.34.67.44 

Dr. Thomas J. Casadevall 

U.S. Geological Survey 

Box 25046, MS 903 

Denver Federal Center 

Denver, CO 80225 

(303) 236-1080 

FAX: (303) 236-1414 

Dr. Steven N. Carey 

University of Rhode Island 

School of Oceanography 

Kingston, RI 02881 

(401) 792-6222 

FAX: (401) 792-6160 

Dr. Derek J. Coffman 

Atmospheric Sciences Dept., AK-40 

University of Washington 

Seattle, W A 98195 

(206) 543-6027 

FAX: (206) 543-0308 

Mr. Charles F. Criswell 

Federal Aviation Administration 

Alaskan Region 

222 W. Seventh Ave., #14 

Anchorage, AK 99513-7587 

(907) 271-5470 

FAX: (907) 276-3998 

Dr. Real D'Amours 

Canadian Meteorological Centre 

2121 North Service Road, Suite 200 

Trans Canada Highway 

Dorval, Quebec H9P 1 J3 

CANADA 

(514) 421-4684 

FAX: (514) 421-4639 

Mr. Douglas D. D'Autrechy 

Science Applications International Corporation 

1710 Goodridge Dr. 

Mclean, VA 22102-1302 

(703) 556-7142 

FAX: (703) 356-8408 

Dr. John N. Davies 

Geophysical Institute 

University of Alaska Fairbanks 

Fairbanks, AK 99775-0800 

Anchorage, AK 99508 

(907) 474-4764 

FAX: (907)474-7290 

Mr. Kenneson G. Dean 

Geophysical Institute 

University of Alaska Fairbanks 

Fairbanks, AK 99775-0800 

(907) 47 4-4764 

FAX: (907) 474-7290 

Dr. Rand Decker 

Department of Civil Engineering 

3220MEB 

University of Utah 

Salt Lake City, Utah 84112 

(801) 581-3403 

FAX: (801) 581-8692 

Mr. Scott D. Doiron 

ST Systems Corporation 

4400 Forbes Boulevard 

Lanham, MD 20706 

(301) 286-8036 

FAX: (301) 286-3460 

Dr. Michael Dunn 

Calspan Advanced Technology Center 

4455 Genesee St. 

Buffalo, NY 14225 

(716) 631-6747 

FAX: (716) 631-6815 

Dr. James S. Ellis 

Lawrence Livermore National Laboratory 

Box 808 (L-262) 

Livermore, CA 94551 

(415) 422-1808 

FAX: (415) 423-4527 

Dr. James E. Evans 

Weather Sensing Group 

Room HW29-119B 

M.I.T. Lincoln Lab- P.O. Box 73 

Lexington, MA 02139 

(617) 981-7433 

FAX: (617) 981-0632 

Authors' Address list 49 
Captain Peter M. Foreman 

Air Traffic Services Committee 

5351 Parker A venue 

Victoria, B.C., V8Y2Nl 

CANADA 

(604) 658-8045 

FAX: (604) 276-8923 

Mr. Tom Fox 

International Civil Aviation Organization (ICAO) 

100 Sherbrooke St. West 

Montreal, Quebec H3A 2R2 

CANADA 

(514) 285-8194 

FAX: (514) 288-4772 

Dr. Peter Francis 

Planetary Geosciences 

University of Hawaii 

2525 Correa Road 

Honolulu, HI 96822 

(808) 956-3163 

FAX: (808) 956-6322 

Dr. Charles Gallaway 

Department of Defense 

6801 Telegraph Road 

Alexandria, VA 22310-3398 

(703) 325-1282 

FAX: (703) 325-2957 

Dr. M. C. Gerbe 

Universite Blaise Pascal & C.N.R.S. 

Unite de Recherche Associee n°10 

5 rue Kessler 

63038 Clermont-Ferrand Cedex 

FRANCE 

73.40.63.63 

FAX: 73.34.67.44 

Dr. J. S. Gilbert 

Department of Geology 

University of Bristol 

Wills Memorial Building 

Queens Road, Bristol BS8 lRJ 

UNITED KINGDOM 

(0272) 303030, ext. 4795 or 0272 

FAX: (0272) 253385 

50 Authors' Address list 

Dr. Laurie S. Glaze 

University of Hawaii 

2525 Correa Road 

Honolulu, HI 96822 

(808) 956-3163 

FAX: (808) 956-6322 

Dr. Alain Gourgaud 

Universite Blaise Pascal & C.N.R.S. 

Unite de Recherche Associee n°10 

5 rue Kessler 

63038 Clermont-Ferrand Cedex 

FRANCE 

73.40.63.63 

FAX: 73.34.67.44 

Mr. Edward Haeseker 

Alaska Airlines 

P.O. Box 68900 

Seattle, WA 98168 

(206) 433-3200 

FAX: (206) 433-6838 

Mr. Robert F. Hamley 

National Weather Service 

FAAARTCC 

3101 Auburn Way South 

Auburn, WA 98002 

(206) 390-5401 

FAX: (206) 931-5208 

Dr. David M. Harris 

Geographic Systems 

270 Boice St. S. 

Salem, Oregon 97302 

(503) 585-6230 

Dr. Ulli G. Hartman 

Perkin-Elmer Corporation 

2771 N. Garey Ave. 

Pomona, CA 91767 

(714) 593-3581 

FAX: (714) 596-2301 

Dr. Norman Hassel 

Unisys Defense Systems 

Marcus A venue 

Great Neck, NY 11020 

(516) 574-1917 

FAX: (516) 574-1967 
Dr. Grant Heiken 

ESS-1, Geology I Geochemistry 

MIS D-462 

Los Alamos National Laboratory 

Los Alamos, NM 87545 

(505) 667-8477 

FAX: (505) 667-3494 

Dr. Robert H. Hertel 

Perkin-Elmer Corporation 

2771 N. Garey Ave. 

Pomona, CA 91767 

(714) 593-3581 

FAX: (714) 596-2301 

Dr. Catherine J. Hickson 

Geological Survey of Canada 

100 West Pender Street 

Vancouver, B.C. V6B 1R8 

CANADA 

(604) 666-395510539 

FAX: (604) 666-1124 

Dr. Peter W. Hobbs 

Atmospheric Sciences Department 

AK 40, University of Washington 

Seattle, WA 98195 

(206) 543-6027 

FAX: (206) 543-0308 

Dr. Richard P. Hoblitt 

U.S. Geological Survey 

5400 MacArthur Blvd. 

Vancouver, WA 98661 

(206) 696-7899 

FAX: (206) 696-7866 

Dr. Frank R. Honey 

SpecTerra Systems Pty Ltd 

43 Hobbs Avenue 

Dalkeith, Western Australia 6009 

AUSTRALIA 

61 (9) 389-8050 

FAX: 61 (9) 386-7935 

Mr. Edward F. Hudson 

Unisys Defense Systems, Inc. 

Marcus A venue 

Great Neck, NY 11020 

(516) 574-1917 

FAX: (516) 574-1967 

Mr. Gary L. Hufford 

National Weather Service 

222 W. 7th Ave., #23 

Anchorage, AK 99513 

(907) 271-3886 

FAX: (907) 271-3711 

Dr. Lee Huskey 

School of Public Affairs 

University of Alaska Anchorage 

3211 Providence Drive 

Anchorage, AK 99508 

(907) 786-1916 

FAX: (907) 786-7739 

Mr. K. Ishihara 

Koto University 

Yokoyama, Sakurajima 

Kagoshima 891-14 

JAPAN 

81-992-93-2058 

FAX: 81-992-93-4024 

Dr. R. Wally Johnson 

Bureau of Mineral Resources 

Geology and Geophysics 

GPOBox378 

Canberra ACT 2601 

AUSTRALIA 

61-62-49-9745 

FAX: 61-62-48-8178 

Ms. Chris J onientz-Trisler 

Graduate Program in Geophysics, AK-50 

University of Washington 

Seattle, W A 98195 

(206) 543-8020 

FAX: (206) 543-0489 

Dr. Kosuke Kamo 

Sakurajima Volcanological Observatory 

Koyto University 

Yokoyama, Sakurajima 

Kagoshima 891-14 

JAPAN 

81-992-93-2058 

FAX: 81-992-93-4024 

Mr. Lee Kelley 

National Weather Service 

Coast Guard Base Box 37 

Kodiak, AK 99619 

(907) 487-2101 

Authors' Address Ust 51 
Dr. Juergen Kienle 

Geophysical Institute 

University of Alaska 

Fairbanks, AI< 99775-0800 

(907) 474-5681 

FAX: (907) 474-5618 

Dr. V. Yu. Kirianov 

Institute of Volcanology 

Petropavlosk-Kamchatsky, 

683006, USSR 

Mr. Herschel Knowles 

National Weather Service 

222 W. 7th Ave., #23 

Anchorage, AK 99513 

(907) 271-5132 

FAX: (907) 271-3711 

Dr. Alexander B. Kostinski 

Department of Geological Engineering 

Michigan Technological Univesity 

Houghton, MI 49931 

(906) 487-2531 

FAX: (906) 487-2943 

Mr. Maurice Krafft 

Centre de Volcanologie 

BPS 

68700 Cernay 

FRANCE 

(89) 75.51.56 

FAX: 89.39.97.96 

Dr. Arlin J. Krueger 

Earth Sciences Directorate 

NASA, Goddard Space Flight Center 

Greenbelt, MD 20771 

(301) 286-6358 

FAX: (301) 286-3460 

Dr. John R. Labadie 

JAYCOR 

1901 N. Beauregard Street 

Suite 503 

Alexandria, VA 22311 

(703) 671-7900 

FAX: (703) 820-1017 

52 Authors' Address List 

Dr. S. J. Lane 

Department of Geology 

University of Bristol 

Wills Memorial Building 

Queens Road, Bristol BS8 1RJ 

UNITED KINGDOM 

(0272) 303030, ext. 4795 or 0272 

FAX: (0272) 253385 

Dr. Francois LeGuern 

Institut de Recherche Fondamentale 

U.G. CFR, Bat. 444CEN-Saclay 

91191 Gif Sur Yvette 

FRANCE 

33 1 69082640 

FAX: 331 69088546 

Mr. James S. Lynch 

NOAA/NESDIS 

World Weather Building, Room 410 

Washington, D.C. 20230 

(301) 763-8444 

FAX: (301) 763-8142 

Dr. G. Macedonia 

Centro di Studi per la Geologia 

e Dinamica dell'Appennino- CNR 

via Santa Maria 53 

I -56100 Pisa 

ITALY 

050-47383-6 

FAX: 050-43163 

Mr. J. Owen Maloy 

Perkin-Elmer Corporation 

2771 N. Garey Ave. 

Pomona, CA 91767 

(714) 593-3581 

FAX: (714) 596-2301 

Dr. Allen Mason 

INC-7 MS J-514 

Los Alamos National Laboratory 

Los Alamos, NM 87545 

(505) 667-4534 

FAX: (505) 665-5688 

Mr. Mike Matson 

NOAA/NESDIS 

World Weather Building 

Washington, D.C. 20230 

(301) 763-8142 

FAX: (301) 763-8131 
Mr. Lindsay McClelland 

NHBMRC129 

Smithsonian Institution 

Washington, D.C. 20560 

(202) 357-1511 

FAX: (202) 357-2476 

Mr. Robert G. McGimsey 

U.S. Geological Survey 

4200 University Drive 

Anchorage, AK 99508 

(907) 786-7 454 

FAX: (907) 786-7450 

Dr. Stephen R. McNutt 

1521 Brewerton Drive 

Sacramento, CA 95833 

(916) 322-9317 

FAX: (916) 323-7778 

Mr. Gregory P. Meeker 

U.S. Geological Survey 

Box 25046, MS 903 

Denver Federal Center 

Denver, CO 80225 

(303) 236-1081 

FAX: (303) 236-1414 

Dr. I. V. Melekestsev 

Institute of Volcanology 

Petropavlovsk-Kamchatsky 683006 

USSR 

Captain Edward Miller 

Aviation Weather Committee 

Airline Pilots Association 

4416 Random Ct. 

Annandale, VA 22003 

(703) 978-9298 

FAX: (703) 689-4370 

Dr. Thomas P. Miller 

U.S. Geological Survey 

4200 University Drive 

Anchorage, AK 99508 

(907) 786-7 454 

FAX: (907) 786-7450 

Ing. Subroto Modjo 

Volcanological Survey of Indonesia 

57 Jalan Diponegoro 

Bandung 

INDONESIA 

62-22-72606 

FAX: 62-22-75588 

Mr. Anthony J. Mostek 

NOAA, National Weather Service 

1325 East-West Highway 

SSMC2- 14110 

Silver Spring, MD 20910 

(301) 427-7677 

FAX: (301) 427-7598 

Mr. Tom L. Murray 

U.S. Geological Survey 

5400 MacArthur Blvd. 

Vancouver, WA 98661 

(206) 696-7549 

FAX: (206) 696-7866 

Mr. Thomas M. Murray 

Boeing Commercial Airlines 

P.O. Box 3707, MS 69-33 

Seattle, WA 98124-2207 

(206) 234-4919 

FAX: (206) 237-0352 

Mr. Mark E. Musolf 

United Technologies- Norden Systems 

P.O. Box 5300 

Norwalk, Connecticut 06856 

(203) 852-7533 

FAX: (203) 852-7423 

Ms. Bobbie Myers 

U.S. Geological Survey 

5400 MacArthur Blvd. 

Vancouver, WA 98661 

(206) 696-7908 or 7906 

FAX: (206) 696-7866 

Dr. Reginald E. Newell 

Department of Earth, Atmospheric and 

Planetary Sciences, 54-1824, 

Massachusetts Institute ofT echnology 

Cambridge, MA 02139 

(617) 253-2940 

FAX: 253-6208 

Authors' Address Ust 53 
Dr. Christopher G. Newhall 

U. S. Geological Survey, MS 905 

12201 Sunrise Valley Dr. 

Reston, VA 22092 

(703) 648-6709 

FAX: (703) 648-6717 

Mr. Robert Oeding 

PDA Engineering 

Program Man~ger 

2975 Red Hill A venue 

Costa Mesa, CA 92626 

(714) 540-8900 

FAX: (714) 545-9434 

Mr. Saburo Onodera 

Meteorology Section, Flight Operations Dept. 

Japan Air Lines Co., Ltd. 

JAL Operation Center Bldg. 

1-1 Hanedakuko 2 Chome 

Ota-Ku, Tokyo 144 

JAPAN 

81-3-3747-3357 

FAX: 81-3-3747-4619 

Mr. D. H. Parkinson 

National Weather Service 

FAAARTCC 

3101 Auburn Way South 

Auburn, W A 98002 

(206) 390-5401 

FAX: (206) 931-5208 

Dr. Papale 

Istituto Nazionale di Geofisics 

via di Villa Ricotti 42, 

I-00100 Roma 

ITALY 

Dr. M. T. Pareschi 

Centro Ricerca mM, 

via Santa Maria 67, 

I56100 Pisa 

ITALY 

Mr. John F. Paskievitch 

U. S. Geological Survey 

4200 University Dr. 

Anchorage, Alaska 99508 

(907) 786-7 454 

FAX: (907) 786-7450 

54 Authors' Address List 

Dr. David Pieri 

MS 183-501 

Jet Propulsion Laboratory 

CAL TECH 

Pasadena, CA 91109 

(818) 354-6299 

FAX: (818) 354-0966 

Mr. John Power 

Geophysical Institute 

University of Alaska Fairbanks 

Fairbanks, AK 99775-0800 

(907) 474-5333 

FAX: (907) 474-5618 

Mr. Rodney Potts 

Bureau of Meteorology 

GPO Box 1289K 

Melbourne 

Victoria 3001 

AUSTRALIA 

61-3-6694584 

FAX: 61-3-6694695 

Dr. A.J. Prata 

CSIRO, Division of Atmospheric Research 

Private Bag No. 1 

Mordialloc 

Victoria 3195 

AUSTRALIA 

(613) 586-7681 

FAX: (613) 586-7600 

Mr. Zygmund J. Przedpelski 

General Electric Corp. Maildrop J -60 

P.O. Box 15630 

Evendale, OH 45215 

(513) 243-4908 

FAX: (513) 243-0164 

Dr. Lawrence F. Radke 

National Center for Atmospheric Studies 

P. 0. Box 3000 

Boulder, CO 80307-3000 

(303) 497-1032 

FAX: (303) 497-1092 

Dr. Herbert A. Roeder 

Perkin-Elmer Corporation 

2771 N. Garey Ave. 

Pomona, CA 91767 

(714) 593-3581 

FAX: (714) 596-2301 
Dr. William I. Rose 

Department of Geological Engineering 

Michigan Technological Univesity 

Houghton, MI 49931 

(906) 487-2531 

FAX: (906) 487-2943 

Dr. Mauro Rosi 

Dipartimento di Scienze della Terra 

via Santa Maria 53, 

I-56100 Pisa ITALY 

Dr. Yosihiro Sawada 

Shizuoka Meteorological Observatory 

2-1-5 Magarikane 

Shizuoka 422 

JAPAN 

054-286-6919 

FAX: 81 054-283-6922 

Dr. R. Santacroce 

Dipartimento di Scienze dalla Terra 

via Santa Maria 53, 

I -56100 Pisa, ITALY 

Dr. Thomas W. Schlatter 

NOAA Forecast Systems Laboratory 

NOAA/ERL/FSL R/E/FS1 

325 Broadway 

Boulder, CO 80303 

(303) 497-6938 

FAX: (303) 497-6750 

Mr. David J. Schneider 

Department of Geological Engineering 

Michigan Technological Univesity 

Houghton, MI 49931 

(906) 487-2531 

FAX: (906) 487-2943 

Dr. Charles C. Schnetzler 

Earth Sciences Directorate 

NASA, Goddard Space Flight Center 

Greenbelt, MD 20771 

(301) 286-3532 

FAX: (301) 286-4098 

Dr. William E. Scott 

U.S. Geological Survey 

5400 MacArthur Blvd. 

Vancouver, WA 98661 

(206) 696-7909 

FAX: (206) 696-7866 

Dr. Stephen Self 

Department Geology and Geophysics 

University of Hawaii 

2525 Correa Road 

Honolulu, HI 96822 

(808) 956-5996 

FAX: (808) 956-2538 

Dr. Tom Simkin 

NHBMS119 

Smithsonian Institution 

Washington, OC 20560 

(202) 357-2786 

FAX: (202) 357-2476 

Dr. G. E. Sigvaldason 

WOVO and the Nordic 

Volcanological Institute, 

University of Iceland 

101 Reykjavik, Iceland 

(354) 1-694300 

FAS: (354) 1-29767 

Mr. Tumpal Situmorang 

Volcanological Survey of Indonesia 

57 Jalan Diponegoro 

Ban dung 

INDONESIA 

62-22-72606 

FAX: 62-22-75588 

Mr. Arthur H. Smith 

NOAA/NWS 

National Meteorological Center 

World Weather Building, Rm 402 

Washington, D.C. 20230 

(301) 763-8441 

FAX: (301) 763-8131 

Dr. Indroyono Soesilo 

BPPT -18th Floor 

Jl. M. Thamrin 8 

Jakarta 10340 

INDONESIA 

FAX: (21) 324-255/(21) 324-9908 

Dr. R. S. J. Sparks 

Department of Geology 

University of Bristol 

Wills Memorial Building 

Queens Road, Bristol BS8 1 RJ 

UNITED KINGDOM 

(0272) 303030, ext. 4795 or 0272 

FAX: (0272) 253385 

Authors' Address Ust 55 
Dr. David Stone 

Department of Geology and Geophysics 

University of Alaska 

Fairbanks, AK 99775 

(907) 47 4-7565 

FAX: (907) 474-5163 

Dr. Melvin Stone 

ATC Surveillance Group 

M.I. T. Lincoln Laboratory 

Lexington, MA 02173-9108 

(617) 981-7426 

FAX: (617) 981-3495 

Dr. Barbara J. B. Stunder 

NOAA/ Air Resources Laboratory 

1325 East-West Highway, Room 9358 

Silver Spring, MD 20910 

(301) 427-7684 

FAX: (301) 427-8119 

Dr. Thomas J. Sullivan 

Lawrence Livermore National Laboratory 

Box 808 (L-262) 

Livermore, CA 94551 

(415) 422-1808 

FAX: (415) 423-4527 

Dr. Donald A. Swanson 

U.S. Geological Survey 

Department of Geological Sciences 

AJ-20, 

University of Washington 

Seattle, W A 98195 

(206) 543-1094 

FAX: (206) 543-5587 

Dr. Samuel E. Swanson 

Department of Geology and Geophysics 

University of Alaska 

Fairbanks, AK 99775 

(907) 47 4-7565 

FAX: (907) 474-5163 

Dr. Widen Tabakoff 

Department of Aerospace Engineering 

University of Cincinnati, MD 70 

Cincinnati, OH 45221 

(513) 556-3226 

FAX: (513) 556-5038 

56 Authors' Address Ust 

Dr. Makoto Tahira 

Koyto University 

Yokoyama, Sakurajima 

Kagoshima 891-14 

JAPAN 

81-992-93-2058 

FAX: 81-992-93-4024 

Dr. Hiroshi L. Tanaka 

Geophysical Institute 

University of Alaska Fairbanks 

Fairbanks, AK 99775-0800 

(907) 474-5516 

FAX: (907) 474-7290 

Mr. George J. Theisen 

USDA, Forest Service 

Gifford Pinchot National Forest 

Vancouver, WA 98668 

(206) 696 7856 

FAX: (206) 696 7863 

Dr. Robert I. Tilling 

U.S. Geological Survey 

MS910 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5235 

FAX: (415) 329-5110 

Mr. Michael A. Tomlinson 

Aviation Services Branch 

NOAA-National Weather Service 

1325 East-West Highway 

Silver Spring, MD 20910 

(301) 427-7726 

FAX: (301) 427-7598 

Dr. Bradford H. Tuck 

School of Public Affairs 

University of Alaska Anchorage 

3211 Providence Drive 

Anchorage, Alaska 99508 

(907) 786-1915 

FAX: (907) 786-7739 

Mr. Jerald Uecker 

NOAA-National Weather Service 

Aviation Services Branch 

1325 East-West Highway 

Silver Spring, MD 20910 

(301) 427-7726 

FAX: (301) 427-7598 
Mr. Peter L. Versteegen 

Science Applications International Corporation 

1710 Goodridge Dr. 

McLean, VA 22102-1303 

(703) 821-4517 

FAX: (703) 356-8408 

Dr. Pierre M. Vincent 

Universite Blaise Pascal & C.N.R.S. 

Unite de Recherche Associee n°10 

5 rue Kessler 

63038 Clermont-Ferrand Cedex 

FRANCE 

73.40.63.63 

FAX: 73.34.67.44 

Major Doug Wade 

Headquarters, Defense Nuclear Agency 

6801 Telegraph Road 

Alexandria, VA 22310-3398 

(703) 325-1054 

FAX: (703) 325 2957 

Dr. G. P. L. Walker 

University of Hawaii at Manoa 

Dept. of Geology and Geophysics 

2525 Correa Road 

Honolulu, HI 96822 

(808) 956-5996 

FAX: (808) 956-2538 

Dr. Louis S. Walter 

Laboratory for Terrestrial Physics 

NASA, Goddard Space Flight Center 

Greenbelt, MD 20771 

(301) 286-2538 

FAX: (301) 286-9200 

Mr. Alan T. Weaver 

Pratt & Whitney 

Commerical Engine Business 

400 Main Street M/S 162-30 

East Hartford, CT 06108 

(203) 565-3513 

FAX: (203) 565-1568 

Mr. Anders Westman 

Alaska International Airport System 

P.O. Box 190649 

Anchorage, AK 99519-0649 

(907) 266-2546 

FAX: (907) 243-0663 

Mr. Frank Whitby 

Bureau of Meteorology 

GPO Box 1289K 

Melbourne 

Victoria 3001 

AUSTRALIA 

61-3-6694584 

FAX: 61-3-6694695 

Mr. Larry Whiting 

Geophysical Institute 

University of Alaska Fairbanks 

Fairbanks, AK 99775-0800 

(907) 474-4764 

FAX: (907) 474-7290 

Dr. C. J. N. Wilson 

Department of Earth Sciences 

University of Cambridge 

Downing Street 

Cambridge CB2 3EQ 

UNITED KINGDOM 

Dr. Kenneth Wohletz 

INC-7 MS J-514 

Los Alamos National Laboratory 

Los Alamos, NM 87545 

(505) 667-4534 

FAX: (505) 665-5688 

Mr. Lester "Bill" Zinser 

1155 Lakeside Dr. #803 

Grand Junction, CO 81506 

(303) 245-2936 

Authors' Address Ust 57 
ORGANIZING COMMITIEE ADDRESSES 

Mr. John Amatetti 

Aerospace Industries 

1250 I Street N. W., Suite 1100 

Washington, D. C. 20005 

(202) 371-8417 

FAX: (202) 371-8470 

Dr. Thomas J. Casadevall 

U. S. Geological Survey 

Box 25046, MS 903 

Denver Federal Center 

Denver, CO 80225 

(303) 236-1080 

FAX: (303) 236-1414 

Mr. Donald D. Engen 

President, AOP A Air Safety 

Foundation 

421 Aviation Way 

Frederick, Maryland 21701 

(301) 695-2000 

FAX: (301) 695-2375 

Dr. Grant Heiken 

ESS-1, MIS D-462 

Los Alamos National Laboratory 

Los Alamos, NM 87545 

(505) 667-8477 

FAX: , (505) 667-3494 

Mr. Nicholas Krull 

Federal Aviation Administration 

800 Independence Ave. S. W. 

Washington, D. C. 20591 

(202) 267-8933 

FAX: (202) 267-3507 

Dr. Robert E. Machol 

Federal Aviation Administration 

800 Independence Ave. S. W. 

Washington, D. C. 20591 

(202) 267-9451 

FAX: (202) 267-5117 

Mr. Michael Matson 

NOAA/NESDIS 

World Weather Building 

Washington, D.C. 20230 

(301) 763-8142 

FAX: (301) 763-8131 

58 Organizing Committee Addresses 

Captain Edward Miller 

Airline Pilots Association 

4416 Random Ct. 

Annandale, VA 22003 

(703) 978-9298 

FAX: (703) 689-4370 

Genice Morgan 

Air Transport Association 

1709NewYorkAvenueN. W. 

Washington, D. C. 20006 

(202) 626-4008 

FAX: (202) 626-4149 

Mr. Anthony Mostek 

NOAA, National Weather Service 

1325 East-West Highway 

SSMC2 -14110 

Silver Spring, MD 20910 

(301) 427-7677 

FAX: (301) 427-7598 

Dr. Christopher G. Newhall 

U. S. Geological Survey, MS 903 

12201 Sunrise Valley Dr. 

Reston, VA 22092 

(703) 648-6709 

FAX: (703) 648-6717 

Mr. William Phaneuf 

Airline Pilots Association 

4416 Random Ct. 

Annandale, VA 22003 

(703) 978-9298 

FAX: (703) 689-4370 

Mr. Zygmund J. Przedpelski 

General Electric Corp. Maildrop J-60 

P. 0. Box 15630 

Evendale, OH 45215 

(513) 243-4908 

FAX: (513) 243-0164 

Mr. Donald Trombley 

Air Transport Association 

1709 New York Ave. N. W. 

Washington, D.C. 20006 

(202) 626-4026 

FAX: 626-4149 

Mr. Robert Vandel 

Flight Safety Foundation 

2200 Wilson Blvd., Suite 500 

Arlington, VA 22201-3306 

(703) 522-8300 

FAX: (703) 525-6047 

Helen Weston 

Air Transport Association 

17098 New York Ave., N. W. 

Washington, D. C. 20006 

(202) 626-4060 

FAX: (202) 626-4149 

*U.S. GOVERNMENT PRINTING OFFICE: 1991-573-049/26040