Augustine: An Alaskan Volcano in Action Dolores Neshyba-Bird, 19 April 2006, ES767 Global Tectonics

Augustine: An Alaskan Volcano in Action

Augustine as viewed from the south on January 12, 2006. Image courtesy of the Alaskan Volcano Observatory/United States Geological Survey, Image creator: Game McGimsey

TABLE OF CONTENTS

INTRODUCTION
TECTONIC HISTORY
VOLCANIC HAZARDS
MONITORS OF AUGUSTINE
CONCLUSION
REFERENCES

INTRODUCTION

Augustine is an active, center dome cluster volcano located in Cook Inlet, Alaska. This volcano has come under intense scrutiny by the public and scientific communities due to its close proximity to several populated areas. There is some concern that if it experiences a major eruption, a tsunami may result. A tsunami would endanger many coastal towns located in Cook Inlet. Recent advances in technology have enabled these communities to monitor the volcano's activity. Their goal is to be able to provide an advanced, accurate and timely warning in the event of a major eruption, a tsunami or other hazardous tectonic condition. This goal is beginning to be realized. On February 1, 2006, the Alaskan Volcano Observatory (AVO) issued an orange alert indicating a major eruption may be eminent.

TECTONIC HISTORY

The Augustine volcano formed on a small island composed of Jurassic sedimentary rock. Fossil found in this formation identify the rock as part of the Naknek formation consisting of thin bedded dark-grey siltstone and very fine sandstone. Glacially striated exotic stone has been observed in several place on the south flank. These rocks indicate that the last (Late Wisconsin) glaciation (between 30,000 and 23,000 years before the present (yr B.P.) filled Cook Inlet and surrounded the island to a height of between 120 to 290 m.

Augustine is one of many volcanoes created as the Pacific plate is subducted under the North American plate. This area contains 80% of the active volcanoes in the United States today, 8% worldwide. As the plate is subducted, magma from the partially melted Pacific plate rises forming the volcanoes. The Aleutian trench marks the boundary between these two plates. This also marks the upper boundary of the Pacific "ring of fire"- an area of intense tectonic activity circling the Pacific Ocean.

Augustine first became active in the late Pleistocene. The earliest igneous rock that can be traced to its volcanic nature are eruptions of olivine basalt which interacted with water and dactic and rhyodactic pumiceous pyroclastic flows. The volcano historically became active around the year 2200 yr B.P. Geological evidence of numerous debris avalanches have been documented. In recent historic time, a major eruption in 1883 caused the summit to collapse resulting in a debris avalanche which created a tsunami. The tsunami, measuring 6 m above sea level, flowed into English Bay Harbor located on the Kenia Peninsula

Other eruptions occurred in 1935, 1963-4, and 1967. These eruptions were less spectacular than the 1883 eruption, with smaller pyroclastic flow. Augustine erupted explosively in 1976, and again in 1986.

A vigorous eruption column rising over the summit of 1,282-m (4,206 ft)-high Augustine Volcano. Photograph by M.E. Yount, U.S. Geological Survey, March 31, 1986. Picture Date: March 31, 1986 Image Creator: Yount, M. E. Image courtesy of AVO / USGS

Scientists believe Augustine is due for another eruption. Recent volcanic activity has been observed starting in January, 2006. The intensity of the activity has increased causing the AVO to issuer an orange alert - indicating that a major eruption is eminent.

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VOLCANIC HAZARDS

There is some debate on whether a major eruption would cause a tsunami that would threaten the Alaskan population. Early geologists warned of the possibility of a repeat of the 1883 tsunami. (Wahrhaftig, 1965) This concern was echoed in 1991(Waitt,1991). However, a recent study by R. H. Suleimani, (2005) predicts that an eruption would have to have a very large debris avalanche moving at a very high speed and must occur at high tide to have a significant effect on the town of Homer and Sledovia - 70 km to the southeast of Augustine. In his opinion, a tsunami occurring in the Homer area is unlikely. Other coastal areas may not be that fortunate. The National Oceanic Atmospheric Association (NOAA) assessed the tsunami risk attributed to volcanic activity on Augustine and has establish a warning area for the Lower Cook Inlet, north of Barren Island and south of Kalgin Island. The upper Cook Inlet is to shallow for a tsunami to threaten Anchorage. (NOAA, 2006) There is some threat of a pyroclastic flow into the sea, but Augustine is located far enough away from any populated for this to be a concern. Studies predict that the flow would disturb only the area within 6 km of the island.

The most prevalent hazard associated with the Augustine Volcano is the ash plume. Ash plumes are a great threat to air travel in the area. Ingestion of the ash by a jet engine results in a catastrophic failure of the engine. Ash plumes can also shut down commercial fishing operations, shipping lanes, and oil production in the area of the plume.

Map downloaded from the AVO website, date accessed 4/17/06.

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MONITORS OF AUGUSTINE

National Oceanic and Atmospheric Administration

The NOAA has established a West Coast and Alaska Tsunami Warning Center that monitors seismic and volcanic activity. While the tsunami center usually does not monitor volcanic activity, in the case of Augustine, a tsunami event is most likely to result from the collapse of the flank resulting in a debris avalanche into Cook Inlet. Efforts are underway to establish a run-up recorder on the island to give direct evidence of tsunami generation or flank collapse. Based on data obtained from Mount St. Helen and other eruptions, it has determined that an seismic disturbance equivalent to seismic event equivalent to an earthquake of magnitude 4.5 or greater may trigger a tsunami. Prior volcanic activity associated with the eruptions of 1976 and 1986 has been equated to a seismic disturbance of 3.2. In the event of a detected tsunami-related seismic or volcanic event, procedures have been established with local emergency personnel to issue a tsunami warning with the National Weather Service (NWS). The NOAA also maintains the web site NOAA website to monitor tsunami conditions should they occur.

The Alaska Volcano Observatory

Much of the research and observation of Augustine is performed through the AVO. The AVO is a joint program of the United States Geological Survey (USGS), the Geophysical Institute of the University of Alaska Fairbanks (UAFGI), and the State of Alaska Division of Geological and Geophysical Surveys (ADGGS). The AVO maintains a AVO website which provide current and historical information on many active Alaskan volcanoes. The AVO has established two webcam sites: one on the island and one on the beach in Homer - 70 km from Augustine. These webcams provide real time pictures of Augustine activity - when not obscured by darkness or fog or inclement weather. Additionally, satellites have been utilized to provide remote images of Augustine in action - resulting in some spectacular images of the 1986 eruption. The satellites employ the Advanced Very High Resolution Radiometer (AVHRR). The AVO monitors satellite imagery twice a day for thermal anomalies which indicate an upcoming eruption. The AVO also looks for ash plumes from more than 80 West Pacific volcanoes. It coordinates with the Federal Aviation Administration (FAA)and the NWS to track the plumes.

Image False color composite satellite image courtesy of the AVO/USGS. Image creator:Steve Smith

The AVO's primary monitoring tool is a series of seismometers. A seismometer records seismic activity which can indicate magma movement months prior to an eruption. The AVO also employs tools that measure the amount of certain gases in the atmosphere. As magma moves closer to the Earths's surface, various gases are vented. Sulfur dioxide is one gas that is rather easily monitored using a correlation spectrometer (COSPEC). A COSPEC measures the amount of sunlight absorbed by the sulfur dioxide. It can be used on the ground or in flight.

An evolving technology is the use of GPS receiver to monitor surface deformations. Currently, AVO has a series of GPS receiver on Augustine that provide realtime data. The GPS data is compared with in field survey and well as data obtain from Satellite Radar Inferometry (inSar) to determine if the ground surface is swelling, an indication that an eruption is eminent. The AVO also uses electronic distance meters (EDM) to monitor surface changes. The EDM reflect laser beams off targets in the test area to measure distance changes between the target and the EDM.

There are several other remote sensing applications/tools that are being utilized in the process of predicting volcanic activity. Unfortunately, they are beyond the scope of this presentation.

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CONCLUSION

Augustine's location within the Cook Inlet provides scientists with a laboratory environment in which to monitor indications that may help predict the size and timing of its volcanic events. Its close proximity to several populated areas provides the impetus for this type of investigation The costs associated with volcanic activity to local commercial and industrial operations also justifies this continuing research. Remote sensing technology as well as in situ survey are providing data which scientist can interpret to assess the risk and type of volcanic event.

This presentation has been prepared by Dolores Neshyba-Bird to satisfy the requirements for Global Tectonics ES767, Emporia State University, Emporia, KS, J.S. Aber, professor.

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REFERENCES

Alaskan Volcano Observatory. World Wide Web Homepage. http://www.avo.alaska.edu [date accessed: 20 April 2006

Archaeology Vocabulary Glossary. World Wide Web Homepage. http://www.neisd.net/redland/roarch/archvoc.htm[date accessed: 17 April 2006]

Cascade Volcano Observatory. World Wide Web Homepage. http://vulcan.wr.usgs.gov [date accessed: 18 April 2006]

Division of Geological and Geophysical Surveys, Department of Natural Resources, Alaska. World Wide Web Homepage. http://www.dggs.dnr.state.ak.us/ [date accessed: 16 April 2006]

Geology of Lake Clark, National Park Service. World Wide Web Homepage http://www.nps.gov/lacl/geology.htm [date accessed: 16 April 2006]

Journal of Sedimentary Research World Wide Web Homepage. http://jsedres.geoscienceworld.org [date accessed: 19 April 2006]

Lander, J.F. (1996). Tsunamis Affecting Alaska 1737-1996, NGDC Key to Geophysical Record Documentation No. 31, NOAA, NESDIS, NGDC, 195 pp.

Suleimani, E.N., Combellick, R.A., Marriott, D., Hansen, R.A., Venturato, A.J., and Newman, J.C., 2005, Tsunami hazard maps of the Homer and Seldovia areas, Alaska: Alaska Division of Geological & Geophysical Surveys Report of Investigation 2005-2, 28 p., 2 sheets, scale 1:12,500.

United States Geological Survey. World Wide Web Homepage. http://geology.usgs.gov/ [date accessed: 18 April 2006]

Wahrhaftig, Clyde, 1965, Physiographic Divisions of Alaska, Department of the Interior, Geological Survey Professional Paper 482, pp 132

Waitt, R.B., Beget, J.E., 1991, Debris Avalanches from summit domes of Augustine Volcano sometimes cause tsunamis in Cook Inlet, Alaska: Eos, Transactions American Geophysical Union, v. 72, p. 227-228

Waitt, R.B., Beget, J.E., with contributions from Kienle, J., 1996, Provisional Geologic Map of Augustine Volcano, Alaska, USGS Open-File Report 96-516, 42p

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