Volcanic Lake Drainage Events
 The evaluation and assessment of geologic and hydrologic hazards and processes are an important focus of the USGS Alaska Science Center. The Aleutian arc of Alaska contains more than 40 active volcanoes that have erupted historically and volcanic processes associated with eruptive activity pose both proximal and distal hazards. Many active volcanoes in Alaska are located in remote areas, and most of the ground based hazards do not necessarily impact people or communities. The effects of eruptions however, may have significant impacts on local environments and may at times adversely affect fish, wildlife, and flora.
During August 2005 an Alaska Volcano Observatory (AVO) field crew reported that a 1,300 ft (400 m) wide melt-water lake formed in the snow and ice filled summit crater at Chiginagak Volcano sometime since August 2004 . Sometime earlier in summer 2005 a portion of the lake drained over the crater rim. The outflow initiated a volcanic debris flow that caused flooding on nearby Indecision and Volcano Creeks and an unnamed drainage on the Pacific Ocean side of the volcano. The flood added water to an important subsistence use lake (Mother Goose Lake) that caused additional flooding along the headwaters of the King Salmon River. The volcanic mudflow apparently contained acidic water and water vapor that caused extensive vegetation damage along Indecision Creek and the unnamed Pacific drainage. The acidic flood water inundated important salmon spawning habitat and lowered the pH of Mother Goose Lake to values <3.0. 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.
Chiginagak is a symmetric stratovolcano located 175 km (110 mi) south of King Salmon on the Alaska Peninsula. The nearest settlement is Pilot Point, 60 km (37 mi) to the northwest. The upper portion of the volcano is snow- and ice-covered, and a prominent fumarole on the upper north flank at about 5,500 ft (~1,675 m) constantly emits steam and sulfur gases. Historical eruptive activity has been minor and is poorly documented; however, young appearing volcanic deposits are common on the lower slopes of the volcano indicating relatively recent eruptive activity.
 This research project will assess numerical models to explain the evolution of volcanically derived acidic flood waters, release of associated acidic gases and describe its effects on vegetation and fish habitat (chig_veg_damage.JPG). A secondary objective is to evaluate and model the recovery of the system to the influx of acidic water and gas as a means of assessing the long-term hazard posed by recurrent events.
 Principle Investigator: Melissa Pfeffer (mpfeffer@usgs.gov, 907 786 7068)
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