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Alaska Water Science Center

Preliminary Volcano Hazard Assessment for the Emmons Lake Volcanic Center, Alaska

By Christopher F. Waythomas, Thomas P. Miller, and Margaret T. Mangan

U.S. Geological Survey
Scientific Investigations Report 20065248


Summary of Hazards at the Emmons Lake Volcanic Center

The Emmons Lake volcanic center is a large stratovolcano complex on the Alaska Peninsula near Cold Bay, Alaska. The volcanic center includes several ice- and snow-clad volcanoes within a nested caldera structure that hosts Emmons Lake and truncates a shield-like ancestral Mount Emmons edifice. From northeast to southwest, the main stratovolcanoes of the center are: Pavlof Sister, Pavlof, Little Pavlof, Double Crater, Mount Hague, and Mount Emmons. Several small cinder cones and vents are located on the floor of the caldera and on the south flank of Pavlof Volcano. Pavlof Volcano, in the northeastern part of the center, is the most historically active volcano in Alaska (Miller and others, 1998) and eruptions of Pavlof pose the greatest hazards to the region.

Historical eruptions of Pavlof Volcano have been small to moderate Strombolian eruptions that produced moderate amounts of near vent lapilli tephra fallout, and diffuse ash plumes that drifted several hundreds of kilometers from the vent. Cold Bay, King Cove, Nelson Lagoon, and Sand Point have reported ash fallout from Pavlof eruptions. Drifting clouds of volcanic ash produced by eruptions of Pavlof would be a major hazard to local aircraft and could interfere with trans-Pacific air travel if the ash plume achieved flight levels. During most historical eruptions of Pavlof, pyroclastic material erupted from the volcano has interacted with the snow and ice on the volcano producing volcanic mudflows or lahars. Lahars have inundated most of the drainages heading on the volcano and filled stream valleys with variable amounts of coarse sand, gravel, and boulders. The lahars are often hot and would alter or destroy stream habitat for many years following the eruption.

Other stratocones and vents within the Emmons Lake volcanic center are not known to have erupted in the past 300 years. However, young appearing deposits and lava flows suggest there may have been small explosions and minor effusive eruptive activity within the caldera during this time interval. Mount Hague may have experienced minor steam eruptions. The greatest hazards in order of importance are described below and summarized on plate 1.

Table of Contents

Summary of Hazards at the Emmons Lake Volcanic Center

Volcanic-ash Clouds

Volcanic-ash Fallout

Lahars, Lahar-runout Flows, and Floods

Pyroclastic Flow and Surge

Debris Avalanche

Directed Blasts

Volcanic gases

Lava flow

Introduction

Purpose and Scope

Physical Setting of the Emmons Lake Volcanic Center

Prehistoric Eruptive Activity

Historical Eruptive Activity

Hazardous Phenomena Associated with Eruptions

Volcanic Hazards

Volcanic-ash Clouds

Volcanic-ash Fallout

Lahars, Lahar-Runout Flows, and Floods

Debris Avalanche

Pyroclastic Flows and Surges

Directed Blasts

Lava Flows

Volcanic Gases

Event Frequency and Risk

Hazard Warning and Mitigation

References Cited

Glossary


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