Augustine Volcano
From Wikipedia, the free encyclopedia
| Augustine Volcano | |
|---|---|
 Augustine Volcano, 1976 |
|
| Elevation | 4,134 feet (1,260 m) |
| Location | Cook Inlet, Alaska, USA |
| Coordinates | |
| Topo map | USGS Iliamna B-2} |
| Type | Stratovolcano |
| Last eruption | 2006 |
Augustine Volcano is a stratovolcano on Augustine Island in southwestern Cook Inlet in the Kenai Peninsula Borough of southcentral coastal Alaska, 280 kilometres (180 miles) southwest of Anchorage. The Alaska Volcano Observatory currently rates Mount Augustine as Level of Concern Color Code Green for aviation and the Volcano Alert Level is at Normal. Augustine Island has a land area of 83.872 km² (32.383 sq mi), while West Island, just off Augustine's western shores, has 5.142 km² (1.985 sq mi, or 1,270.68 acres). The islands have no population.
Contents |
[edit] Description and geologic history
The nearly circular uninhabited island formed by Augustine Volcano is 12 km (7.5 mi) wide east-west, 10 km (6 mi) north-south; a nearly symmetrical central summit peaks at altitude 1,260 metres (4,134 ft).
Augustine's summit consists of several overlapping lava dome complexes placed during many historic and prehistoric eruptions. Most of the fragmental debris exposed along its slopes comprises angular blocks of dome-rock andesite, typically of cobble to boulder size but carrying clasts as large as 4 to 8 meters (10 to 25 feet), rarely as large as 30 meters (100 ft). The surface of such deposits is skeet, a field of steep conical mounds and intervening depressions with many meters of local relief. En route to Katmai in 1913, Robert F. Griggs had briefly inferred landslide (debris avalanche) as the origin of Augustine's hummocky coastal topography about Burr Point, by geomorphic analogy with the hummocky and blocky deposit of a 1912 landslide near Katmai.
The hummocky deposits on Augustine's lower flanks resemble both topographically and lithologically those of the great landslide or debris avalanche that initiated the spectacular May 18, 1980 eruption of Mount St. Helens. The deposit of that landslide revealed the origin of coarse diamicts with hummocky topography at other strato volcanic cones. Since 1980 many hummocky coarsely fragmental deposits on Augustine's lower flanks have come to be interpreted as deposits of numerous great landslides and debris avalanches.
[edit] Recent eruptions
A March 27, 1986 eruption deposited ash over Anchorage and disrupted air traffic in southcentral Alaska.
On January 11, 1994, Augustine erupted at 13:44 & 14:13 UTC.
In mid-December 2005 a sulfur dioxide-laden plume of steam, hundreds of miniature earthquakes and a new coating of ash over its currently snow-clad peak, taken together, suggested that Augustine was building to a new eruption, likely in 2006. [1]
On January 13, 2006, Augustine again burst at 12:55, 17:47, & 20:20 (and even carrying over into the early morning of January 14 at 01:40 & 03:58) UTC, with the first eruption of the day lasting some 44 minutes, and the second only around 4 minutes, 17 seconds. The eruptions produced a light cloud, sending a plume of ash and steam up into the stratosphere to at least 30,000 feet (9,100 m), up to an unofficial level of 52,000 feet (15,849 m). The days' eruptions caused many delays and some cancellations at nearby Ted Stevens Anchorage International Airport.
On January 17, 2006, Alaska Volcano Observatory recorded a strong seismic signal at 16:58 UTC lasting 5 minutes. It sent an ash plume approximately 45,000 feet (13.6 km) into the air. The seismic activity was equivalent to that noted for the events in the previous week. There were at least 2 flight disruptions, and light ashfall occurred at Seldovia, Port Graham, and Nanwalek.
On January 28, 2006 the Alaska Volcano Observatory recorded explosive eruptions at 0524, 0837, 1104, and 1642 UTC. These eruptions had respective durations of 9, 1, 2, and 3 minutes. Ash drifted southeast and northeast from these eruptions, and reached a maximum height of 30,000 feet (9,144 m). At 2330 UTC a continuous ash emission event began, and continued through the night with plume heights of 30,000 feet (9,100 m).
On January 29, 2006 National Weather Service Radar tracked an ash cloud at 14,000 feet (4,300 m) drifting south toward Kodiak Island. Satellite observations revealed pyroclastic flows near the summit
[edit] Current Activity
On September 22, 2007, the Alaska Volcano Observatory reported that shallow earthquake activity had increased over the week of September 22. However, the activity is less than its level during the months leading up to the 2005-2006 eruption.
[edit] Sensor Networks
The Plate Boundary Observatory, operated by UNAVCO, (http://pbo.unavco.org) has a network of 10 high-precision GPS instruments on the flanks of Augustine. Activity last year claimed two of these sites. The Alaska Volcano Observatory (http://www.avo.alaska.edu) also operates a number of seismometers and tiltmeters all around the volcano, including four webcams.
[edit] References
- Augustine Island and West Island: Blocks 1070 thru 1073, Census Tract 1, Kenai Peninsula Borough, Alaska United States Census Bureau
