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Report on Spurr (United States) — November 1992

Bulletin of the Global Volcanism Network, vol. 17, no. 11 (November 1992)
Managing Editor: Lindsay McClelland.

Spurr (United States) Continued seismicity and gas emission

Please cite this report as:

Global Volcanism Program, 1992. Report on Spurr (United States) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 17:11. Smithsonian Institution.

Volcano Profile |  Complete Bulletin


Spurr

United States

61.299°N, 152.251°W; summit elev. 3374 m

All times are local (unless otherwise noted)


Occasional seismicity has continued at Mt. Spurr since the eruptive episode of 16-17 September. Earthquakes were concentrated in the vicinity of Crater Peak, the S-flank vent that has been the source of the 1992 activity. Focal depths from early November through early December ranged from above sea level to 44 km. In addition to the few locatable events per day, many small earthquakes that could not be precisely located were detected by one or more stations in the area. No strong swarms have occurred since 9-10 November, when a series of shallow events raised alert levels but did not culminate in an eruption. A number of episodes of low-amplitude tremor were recorded at some stations near Crater Peak 26-27 November.

Gas emission continued from Crater Peak, feeding a plume that sometimes rises to 3,300 m. Even though the plume's SO2 content has been below COSPEC detection limits since mid-October, sulfur gases could still be smelled. CO2 content remained above background at near 1,000 metric tons/day (table 1).

Table 1. Emission rates, in metric tons/day, of SO2 and CO2 at Spurr, 8 June 1991-15 November 1992; other events are noted for context. SO2 values, measured by COSPEC, are averages of 2-5 daily aerial observations, taken looking up through the plume. Measured SO2 flux decreased during tremor episodes 3-5 October. CO2 data are from direct plume samples analyzed with a Miran infrared spectrometer. Courtesy of AVO.

Date SO2 CO2
08 Jun 1991 21 --
22 Jul 1991 Very low Very low
21 Aug 1991 0 --
29 Aug 1991 0 --
03 Sep 1991 85 --
22 Nov 1991 0 --
14 May 1992 88 --
27 Jun 1992 Eruption
29 Jun 1992 5 --
18 Aug 1992 Eruption
10 Sep 1992 0 --
16-17 Sep 1992 Eruption
21 Sep 1992 23 --
23 Sep 1992 24 --
24 Sep 1992 79 --
25 Sep 1992 300 11,000
28 Sep 1992 194 12,000
29 Sep 1992 749 8,700
02 Oct 1992 452 --
03 Oct 1992 220 4,800
04 Oct 1992 212 3,500
05 Oct 1992 356 2,900
10 Oct 1992 243 --
14 Oct 1992 47 2,400
15 Oct 1992 64 --
16 Oct 1992 Low Low
19 Oct 1992 Background Background
23 Oct 1992 24 2,100
29 Oct 1992 Background Background
09 Nov 1992 Seismic swarm
10 Nov 1992 Background Background
11 Nov 1992 Background Background
12 Nov 1992 Background 1,100
13 Nov 1992 Background 1,000
15 Nov 1992 Background 1,000

Geologic Background. The summit of Mount Spurr, the highest volcano of the Aleutian arc, is a large lava dome constructed at the center of a roughly 5-km-wide horseshoe-shaped caldera open to the south. The volcano lies 130 km W of Anchorage and NE of Chakachamna Lake. The caldera was formed by a late-Pleistocene or early Holocene debris avalanche and associated pyroclastic flows that destroyed an ancestral edifice. The debris avalanche traveled more than 25 km SE, and the resulting deposit contains blocks as large as 100 m in diameter. Several ice-carved post-caldera cones or lava domes lie in the center of the caldera. The youngest vent, Crater Peak, formed at the breached southern end of the caldera and has been the source of about 40 identified Holocene tephra layers. Eruptions from Crater Peak in 1953 and 1992 deposited ash on the city of Anchorage.

Information Contacts: AVO.