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The Chiginagak Volcanic Lake Drainage Event: Melissa Anne Pfeffer

Project Title: The Chiginagak Volcanic Lake Drainage Event
Mendenhall Fellow: Melissa Anne Pfeffer,
Duty Station: Anchorage, AK
Start Date: October 1, 2007
Education: Ph.D. (Geosciences), Max Planck Institute for Meteorology, 2007
Research Advisors: Carl Markon,; Chris Waythomas,

Project Description: The crater lake of Chiginagak Volcano, located on the Alaska Peninsula, breached its crater walls in the summer of 2005.  The sudden release of the crater lake’s water produced a flood and minor lahar. The crater lake waters were acidic from dissolved fumarolic gases, and the flood damaged and killed vegetation contained within the channels through which it flowed. The flood terminated in the Mother Goose Lake, an important salmon spawning habitat, where two summers later, the salmon have still not returned.  According to local residents, this type of event has occurred before, resulting in complete destruction of the salmon spawning habitat and no fish returning to the affected drainages and Mother Goose Lake for several years. 

The crater lake drainage event at Chiginagak Volcano is unique among observed crater lake breakouts in that the flood was accompanied by a gas-and-aerosol-phase (hereafter referred to as simply gas-phase) flow  that killed vegetation in a large swath above the heights where the flood traveled.  This gas-phase flow appears to have traveled as a dense gravity current, and may have been generated by the sudden release of pressure when the crater lake waters escaped.  This research project will address the question: Why did the crater lake breakout at Chiginagak Volcano produce a gas-phase flow?  To this end, a hydrodynamic model will be used to simulate the water flood and a heavy gas dispersion model will be used to simulate the transport of the gas. The U.S. Geological Survey (USGS) National Elevation Dataset (NED) with a resolution of 60 m×60 m for Alaska will be used to represent the topography of Chiginagak in initial simulations. 

The agent responsible for the gaseous vegetation damage is likely sulfate aerosol and/or HF carried along by CO2.  It is the transport of CO2 that will be simulated by the heavy gas dispersion model, and the ratio of sulfate aerosol and HF to CO2 in the fumarolic gases dissolved in the crater lake will be estimated based on fumarolic gas samples collected at other nearby volcanoes, as the crater lake of Chiginagak is inaccessible.  The gas will be modeled traveling both independently of and on top of the traveling flood waters.  These results will be compared with observations of where the flood and gas-damage occurred, in order to see which transportation mechanism is more consistent with the observed patterns.  Using the more likely transportation scenario, simulations will be repeated with different gas emission rate values to produce gas concentrations at levels sufficiently phytotoxic (for sulfate, HF, and a mixture of the two) to produce the observed region of dead vegetation.  The emission rate needed to reproduce the damaged region most reasonably will be used to calculate how much gas was dissolved in the crater lake at the time of the drainage event. These iterative simulations will be used to see how important the concentration of gas dissolved in the crater lake is for producing a deadly gas-phase flow.  Remote sensing observations of the emission fluxes of SO2 and CO2 from the current crater lake and from a fumarole on the flank of the volcano will be performed to check if the calculated gas dissolved in the lake prior to the breakout is reasonable, while the time over which the gases were dissolving will be based on the volcano's past activity.  The simulation of the transport of the quantity of gas calculated to have been released at Chiginagak will be repeated at another active volcano with crater lake breakouts in order to see if it is Chiginagak’s  distinct  topography or vegetation cover that led to this unique phenomena. It is hoped that communities who live downstream from volcanic lakes can be better protected from this potential risk by understanding what conditions led to this gas-phase occurring at Chiginagak.

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Last modified: 16:08:31 Thu 13 Dec 2012