Vulcan AlaskaEdition

Akutan Peak Elevation:4275 ft Latitude:54.13308째 N Longitude:165.98555째 W Akutan is one of the most volcanically active islands in the eastern Aleutian arc.

Official Name: Akutan Peak Type: Stratovolcano with caldera Latest Activity: 12.18.1992 Seismically Monitored:Yes

TYPE: From Miller and others (1998): “Akutan volcano is a composite stratovolcano with a circular summit caldera about 2 km across and 60 to 365 m deep(Byers and Barth, 1953; Romick and others, 1990; Motyka and others, 1981) and an active intracaldera cinder cone. The caldera rim reaches a maximum altitude of 1303 m at Akutan Peak, the remnant of a pre-caldera cone now filled with a lava plug. The

caldera is breached to the north. Caldera subsidence accompanied or followed eruptions from a series of rim vents. The vestige of a larger caldera, of probable late Pleistocene age and at least in part older than the cone of Akutan Peak, extends 1.5 km southwest of Akutan Peak and is terminated to the north by the younger caldera. Small glaciers fill the older crater and lie within the southwest and southeast margins of the younger caldera.

“The active intracaldera cinder cone is over 200 m high, about 1 km in diameter, and located in the northeast quarter of the caldera. Three small sulfur-lined craters occupy its summit and several fumarole zones are present along its south and southwest flank (Byers and Barth, 1953). A crescent-shaped lake along the inner southwest rim of the caldera and a hot and slightly acidic lake along the northern caldera wall were noted by Byers and Barth in 1948 but Motyka and others

(1981) speculate that these lakes may have been obliterated by more recent activity.

Both lakes drained to the north through a gap in the caldera wall.

Defintions Caldera A caldera is a large, usually circular depression at the summit of a volcano formed when magma is withdrawn or erupted from a shallow underground magma reservoir. The removal of large volumes of magma may result in loss of structural support for the overlying rock, thereby leading to collapse of the ground and formation of a large depression. Calderas are different from craters, which are smaller, circular depressions created primarily by explosive excavation of rock during eruptions.

Pleistocene Age The most recent episode of glaciation, the Pleistocene epoch, is commonly referred to as the Ice Age and began approximately 1.6 million years ago.

During that time there were a number of advances and retreats of the glaciers, which are termed glacial and interglacial stages, respectively. The glaciers of Greenland and Antarctica are remnants of the last glacial advance.

“The lava flows and pyroclastic deposits of Akutan volcano are no older than Pleistocene as Romick and others (1990) report ages of 1.1 +/- 0.1 to 1.8 +/- 0.8 Ma for the oldest of these rocks.

The caldera-forming eruption occurred about 5,200 yBP (Reeder, 1983) and was the source of small volume andesitic pyroclastic-flow deposits in valleys on the north, south, and east sides of the volcano (Miller and Smith, 1987; Romick and others, 1990). Young basal-

tic lava flows, some of which were erupted in 1929, cover the caldera floor south and north of the cinder cone and extend several hundred m downslope through the crater rim gap. Flows extruded in 1947 blanket the central portion of the northwest end of the island at Lava Point, where about 4 square kilometers of jagged aa basalt occurs adjacent to several cinder cones. The entire island is mantled by an ash layer that thickens toward Akutan Peak; land-

slide and mud flow deposits . have concentrated this ejecta in the valleys north and northeast of the caldera and a maximum fill depth of 7 m occurs at Wooly Cove (Finch, 1935). “Active hot springs occur northeast of the caldera at the head of Hot Springs Bay valley and along the shore of Hot Springs Bay; Byers and Barth (1953) and Motyka and others (1990) recorded temperatures between 67 and 84 degrees

C and a pH range of 6.6 to 7. Surface waters of the hot caldera lake were 50 degrees C with a pH of 5.0 and steam issuing from fumaroles along the cinder cone base averaged 96 degrees C (Finch, 1935).�

Recent eruptions produced only small amounts of fine volcanic ash that fell primarily on the upper flanks of the volcano. Small amounts of ash fell on the Akutan Harbor area during eruptions in 1911, 1948,

1987, and 1989. Plumes of volcanic ash are the primary hazard associated with eruptions of Akutan Volcano and are a major hazard to all aircraft using the airfield at Dutch Harbor or approaching Akutan Island. Eruptions similar to historical Akutan eruptions should be anticipated in the future. Although unlikely, eruptions larger than those of historical time could generate significant amounts of volcanic ash, fallout, pyroclastic flows, and lahars

that would be hazardous to life and property on all sectors of the volcano and other parts of the island, but especially in the major valleys that head on the volcano flanks. During a large eruption, an ash cloud could be produced that may be hazardous to aircraft using the airfield at Cold Bay and the airspace downwind from the volcano. In the event of a large eruption, volcanic ash fallout could be relatively thick over parts of Akutan Island and volcanic

bombs could strike areas more than 10 kilometers from the volcano.

A lava flow in 1978 traveled through a narrow breach in the north caldera rim to within 2 km of the coast.

A small lake occupies part of the caldera floor. Two volcanic centers are located on the NW flank: Lava Peak is of Pleistocene age; and, a cinder cone lower on the flank which produced a lava flow in 1852 that extended the shoreline of the island and forms Lava Point. An

older, mostly buried caldera seems to have formed in Pleistocene or Holocene time, while the current caldera formed in a VEI-5 eruption c. 340 AD. The volcano erupted most recently in 1992, but there is still fumarolic activity at the base of Lava Point and there are hot springs North-East of the caldera.

Eruptions and Activity 1996 Earthquakes Intense seismicity was felt by Akutan residents on the evening of 10-11 March 1996. The swarm of 80 earthquakes lasted for 11 hours. The largest earthquake was magnitude 5.1. On 13th March, felt-earthquakes began occurring at a rate of greater than 1/ minute. The largest earthquakes were felt as far away as Dutch Harbor/Unalaska 50 km SW of Akutan.

On 14th March, earthquakes were strong enough to ring the bell in the Russian Orthodox Church, during a second swarm of 120 earthquakes. In total, more than 3000 earthquakes occurred beneath the island. Extensive ground cracking resulted, but no eruption occurred.

1992 Eruptions Small steam and ash eruption occurred at Akutan volcano in April and December 1992.

1991 Eruptions Summit ash emissions began in September, with a plume to 4500 m altitude. Ashfall was reporded at Akutan village.

1990 Eruptions Small ash eruptions were reported in September and October. Maximum height of plumes were 1500 m above the summit.

1989 Eruptions In March 1989 an air shock wave was felt by a pilot flying over the western shore of Akutan volcano. Black ash was emitted to a height of 2,300 m above the volcano.

1988 Eruptions Ash emissions occurred at Akutan volcano between March and June 1988. Most observations were by pilots.

1987 Eruptions On 22nd June 1987 a summit glow was seen by a fisherman in the Bering Sea. Two days later, a pilot reported ash emissions to 1300 m altitude from a large cinder cone in the summit crater.

1986 Eruptions In June, numerous ash emissions to an altitude of 3.5 km were visible from Akutan village.

1980 Eruptions On the 3rd July a recent lava flow that had moved through a breach in the NNW caldera wall was observed.

1978 Eruption In 1978 lava flowed through a gap in the caldera and came within 1 km of the sea in the north.

Strombolian eruptions occurred at the summit.

1977 Eruptions Eruptions began in May, with light brown ash emissions every 15 minutes. Incandescence was noted in some eruptions.

1974 Eruptions In February, ash was emitted hundreds of feet into the air, and lava flowed down the flank.

1973 Eruptions Akutan volcano erupted ash and steam for several months, with the mountain snow-free.

1946-48 Eruptions 1946-48 Eruptions Lava flows occurred at the volcano caldera.

1924 Eruption A lava flow occurred on the floor of the caldera.

Eruptions in the 1850’s A cinder cone and two lava flows were erupted north of Lava Peak. The lava flows formed two lobes which flowed into the sea, forming Lava Point.

Other Eruptions 1912, 1911, 1908, 1907, 1896, 1892, 1887, 1883, 1867, 1865, 1852, 1848, 1845, 1838, 1790

Akutan Summit and Intra Caldera

Culture Akutan Peak Akutan is a wonderful destination for ecotourism.

Hiking on the island is diverse-wildflowers and berries abound on the hills and mountains. There is a thermal hot springs within hiking distance of the village. Hardy souls have climbed all the way to the crater of Akutan volcano, which is about seven miles west of the village. The volcano is active, with steady steam emissions and an occasional dusting of volcanic ash. There are no bears on the island, although you can see an occasional fox, and Akutan and the surrounding islands teem with birds and sea life. The whiskered auklet is found on the nearby Baby Islands, one of only two places it exists in the world. Fishing is excellent in the waters around Akutan, and some of the largest halibut in the world have been caught in Akutan Pass at the west side of the Island.

Akutan is located on Akutan Island in the eastern Aleutians, one of the Krenitzin Islands of the Fox Island group. It is 35 miles east of Unalaska, and 766 air miles southwest of Anchorage. Akutan began in 1878 as a fur storage and trading port for the Western Fur & Trading Company. The company’s agent established a commercial cod fishing and processing business that quickly attracted nearby Aleuts to the community. It was the only whaling station in the Aleutians from 1912 to 1942. The U.S. Government evacuated Akutan residents to the Ketchikan area in June 1942. The village was re-established after the war. Akutan is primarily a non-Native fishing community, although it is home to a traditional Aleut village.

Commercial fishing and fish processing dominate Akutan’s cash-based economy. Trident Seafoods operates a major bottomfish plant west of the City.

Deep Sea Fisheries also has a permanent process-

ing vessel in the bay. Nine residents hold commercial fishing permits. Subsistence hunting and fishing activities are minimal because the majority of residents are employed. The majority of the population lives in group quarters facilities.

Transportation Boats and amphibious aircraft are the only means of transportation into Akutan. Cargo is delivered weekly by freighter from Seattle. Akutan has no airstrip, however, a seaplane base is available. Daily air service is available from nearby Unalaska.

Climate Akutan lies in the maritime climate zone. Temperatures range from 22 to 55. Precipitation averages 27.5 inches per year. Storms are frequent in the winter and fog is common in the summer.

Akutan has a deep and protective bay and is actually 40 miles closer to the “crab fishing grounds” than Dutch Harbor. Although Akutan has no landing strip, has only 100 or so fulltime residents, and has no paved roads–only wooden boardwalks, is still one of the busiest fishing ports in the country, and has one of the largest processors–Trident Seafoods–about 1/4 mile away from the village of Akutan. For this reason, and it’s remoteness,it was featured on Deadilest Catch.

First formed in 1878 as a fur trading post, Akutan village was also one of the first introduced to the crab fishing industries in the 1940′s and was home to several floating processors at that time.

In 1942, when the Japanese attacked Unalaska, all residents were evacuated and thus had to re-establish themselves as a village in 1944. Finally in 1979, it was incorporated as the “city” of Akutan.

Akutan is not only home to some of the busiest fishing ports, but also superstition. There is a tradition of throwing rocks onto a rock pile, if the rock stays on top, then you are fine and healthy.

However; if the rock falls off, then you will die within the next year.

Wolfgang Brinck

Kurt Schmidt participating in the rock toss.

Akutan Bay separtes the harbor from the Spring.

While the volcano sits in the background.

Volcanologist set up equiptment near Akutan’s hot springs.

Akutan Village

Akutan Canary

Pavlof Volcano

Elevation: 8261 ft Latitude: 55.4173째 N Longitude: 161.8937째 W Official Name:Pavlof Volcano Type:Stratovolcano Latest Activity: August 15, 2007 Seismically Monitored: Yes

The most active volcano of the Aleutian arc

Type: Pavlof is a composite cone volcano located in the southwestern region of Alaska about 600 kilometers southwest of Anchorage. At its summit Pavlof reaches an elevation of 8,262 ft (2518).

The volcano consists of andestic magma, that contains an intermediate content of gases. Emission of lava and ash has occurred during the volcanoes eruptive stage.

Other geologic events are also related to the volcanic

activity at Pavlof. Seismic activity, mudflows, and flooding have also occurred due to Pavlof’s eruptive process.

Pavlof has been in a period of eruptive pause during the previous six weeks. Even during these pauses the threat of violent volcanic activity is always present. Fortunately the volcano is located in a fairly remote region and does not pose a great threat to many people.

Form and structure

Mount Pavlof is a largely snow-covered, cone-shaped mountain with a high ridge extending to the southwest towards Little Pavlof. The volcano is approximately 7 km in diameter and has active vents on the north and east sides close to the summit (McNutt and others, 1991). It is situated high on the northeastern flank of Emmons Lake caldera along a northeast-trending alignment of vents that includes Little Pavlof, Pavlof Sister, and several intracal-

dera cones (Kennedy and Waldron, 1955). The composite volcano is relatively undissected and is probably Holocene in age. Pavlof lies within the Shumagin seismic gap (Davies and others, 1981).

Volcanic activity Mount Pavlof is the most active volcano in the Aleutian volcanic arc with almost 40 relatively well-documented eruptions dating

back to 1790 (Newhall and Dzurisin, 1988; Smithsonian Institution, 1976-1988; McNutt, 1987; Coats, 1950; Jaggar, 1932). It is so consistently active that a question sometimes arises as to what constitutes a separate eruption. Some Pavlof eruptions have been short-lived (1-2 days duration) and similar eruptions in the past may have occurred unnoticed in the sparsely populated region. Pavlof eruptions are typically strombolian to vulcanian in character and

consist of rhythmic ejection of incandescent bombs and ash to heights of 200-300 meters above the summit (McNutt and others, 1991); spatter-fed lava flows emanate from the summit vents on occasion. Short-lived volatile-rich vulcanian ash columns reaching to heights of 10 kilometers or more have been noted, usually at the beginning of an eruption.

Eruptions tend to be either magmatic or phreatomagmatic and McNutt (1987) found a correlation between

seismic activity and type of eruption. Strong volcanic tremor accompanied major Strombolian magmatic eruptions, whereas episodes of explosion quakes, with little to no volcanic tremor, were diagnostic of minor phreatomagmatic events.

The largest historical eruption of Pavlof occurred on December 6-7, 1911 at the end of a five year period of activity. A fissure vent opened along the north flank, large blocks were ejected, and lava flows issued from the

fissure (McNutt, 1987). A recent vigorous eruptive period began mid-April, 1986 and continued through August, 1988 (Smithsonian Institution, 1986-88; McNutt and others, 1991). Frequent steam and ash emission, explosions, and strong tremors accompanied summit lava fountaining that fed several agglutinate lava flows, which in turn produced a number of both hot and cold, extensive mudflows.During the early course

of the eruption, the eruptive vent shifted from the north to the east side of the summit. The most recent eruptive episode at Mount Pavlof began about September 11, 1996 and continued into early 1997 (Neal and McGimsey, 1997). The eruptive activity was strombolian in character and similar to most Pavlof eruptions. Intermittent explosive activity and lava fountaining were recorded from two closely-spaced vents high on the

northwest summit of the volcano. Incandescent spatter, spatter-fed flows, and small lahars moved down the northwest flank of the volcano for the next four months melting a narrow channel through snow and ice. Occasional elongate plumes that rose to a maximum of 10 kilometers above sea level (generally less than 6 kilometers) and extended up to several hundred kilometers downwind

were detected on satellite images and reported by pilots. These clouds consisted chiefly of vapor and gas with minor amounts of ash.

Light ash fall was reported on several occasions from nearby communities.

Composition Mount Pavlof is composed of basaltic andesite flows and pyroclastic rocks that overlap similar rocks from nearby Little Pavlof.

The flows are moderately

phyric with about 25% phenocrysts, mostly plagioclase with minor olivine and clinopyroxene. The agglutinate flows of 1987 are of similar andesitic composition.

Volcano Structure: The volcano is 7km in diameter and has two active vents, one located on the northern side and the other on the eastern side (Miller et al, 1998) and the overall outline of the volcano appears cone shaped.

Historic Activity: Pavlof has been erupting since 1790 and has experienced more then forty periods of small to moderate activity since this time (Decker & Decker, 1998) with the latest eruption occurring from September 1996 to January 1997 (Wallace et al, 2000).

The type of eruptions normally seen from Pavlof consist of Strombolian and Vulcanian eruptions where the main components are bombs and ash that normally reach heights of around

200 to 300m (Miller et al, 1998).

The largest eruption in Pavlof’s history occurred in 1911 when a fissure opened expelling large lava flows, together with these flows large blocks were expelled from the volcano. In more recent times a period of high activity was noted from 1986 through to 1988 where large volumes of ash and steam were expelled together with lava flows and also lava fountains.

Eruptions and Activity Start Date: 08.15.2007 Stop Date: 09.13.2007 Dating Technique: Historical Records Volcanic Explosivity Index (VEI): 2 Eruptive Characteristics: Central vent eruption Explosive eruption Lava flow(s) Mudflow(s) (lahars) “During the night, an intense thermal anomaly (TA) was visible in satellite images (Advanced Very High Resolution Radiometer-AVHRR), and seismic activity continued to increase in both number and duration of events per hour, clear signs that the unrest was escalating. On the morning of August 15, based on observations of the TA and increasing

seismicity, AVO elevated the Aviation Color Code/ Volcano Alert Level to ORANGE/WATCH and announced that an eruption was expected. With the upgrade in color code, AVO began 24-hour surveillance of the volcano. Later in the day, AVO received eyewitness accounts from mariners of incandescent blocks rolling down the eastern-southeastern flank of the volcano during the previous night, beginning around midnight. Pilots reported a thin, low-level ash plume extending a few kilometers southwest from the summit. After receiving these reports, AVO established that the volcano was in eruption.

Aerial photographs taken on August 15 show lava fountaining from a vent located about 200 m (650 ft) below the summit [see fig. 26 in original text].

“On August 16, strong seismic signals recorded at a single station (PVV), located 8.5 km (5.3 mi) southeast of the summit, heralded the passage of lahars down the south flank; more than 41 lahar events would be recorded by this station over the next 29 days. Satellite observations of a strong thermal anomaly (TA) [see fig. 27 in original text] and nighttime incandescence at the summit reported by local residents were indications of vigorous lava eruption at the summit vent [see fig. 28 in original text]. The seismic network recorded long periods of volcanic tremor with repetitive explosions that indicated nearly continuous Strombolian eruption.

In addition to the generation of lahars, this activity

produced low-level ash clouds (5-6 km ASL; 3.1-3.7 mi), and a spatter-fed lava flow that descended the southeastern flank. By August 18, AVO personnel in the field reported that vigorous eruption of lava at the summit continued. Using a Forward Looking Infrared (FLIR) camera, they determined that a 20to 50-m-wide, 65- to 165 ft-wide) 600 C (1,112 F) lava flow extended 565 m (1,850 ft) from the vent down the southeast flank [see figs. 29 and 30 in original text]. Thermal data collected the next day indicated that the outer part of this flow was about 140C (284 F) and had cooled considerably. The vent crater for the last eruption of Pavlof, in 1996, was located on the upper northwestern side of the summit. For this eruption, the active vent migrated to the upper

southeastern side, about 200 m (650 ft) below the summit [see figs. 31-33 in original text]. “Seismicity at Pavlof was elevated and steady throughout the remainder of August and then began waxing and waning for the first week of September. A strong TA was present in satellite images, even through clouds, during this time. During the second week of September, the seismicity began showing signs of a steady decrease [see fig. 34 in original text], and by September 13, seismicity decreased to low levels and only a minor steam plume was visible above the volcano. A TA was last seen on September 15, and AVO declared that the activity had reached a lull by September 17. An AVO field

crew with clear views reported that all eruptive activity had ceased during their visit on September 19, and the Aviation Color Code /Volcano Alert Level was downgraded to YELLOW/ADVISORY on September 20. The next 2 weeks of low seismicity and no further signs of activity or unrest prompted AVO to declare the eruption over (ending on September 13), and the Color Code/Volcano Alert Level was downgraded to GREEN/NORMAL on October 5. “Ash, a blocky lava flow, and multiple lahars were generated by this eruption. Mixed ash and steam clouds produced during the most energetic eruptive period, mid-August to mid-September, reached altitudes of 5-6 km (about 20,000 ft) ASL. The plumes

were diffuse, drifted primarily to the southeast over the North Pacific Ocean, and many could not be detected in satellite imagery. No ash reportedly fell on nearby communities and there were no significant impacts to aviation. AVO deployed a DRUM aerosol impactor (particle collector) in Sand Point, 90 km (56 mi) east of Pavlof, and collected fine ash (2.5-0.1 ďż˝m). Although no visible ash fallout was observed during aerosol sampling, these results demonstrate that volcanic ash was present in respirable size fractions downwind of the volcano even during periods of low ash emissions (Peter Rinkleff and Cathy Cahill, AVO/UAFGI, written commun., 2010). “Analyzed samples from the lava flow are basaltic

andesite in composition (53% SiO2), which is similar to the products of previous Pavlof eruptions (McNutt and others, 1991; Neal and McGimsey, 1997). Lahars were produced by interaction of hot blocks and spatter from the lava flow with snow and ice on the southeastern flank. The lahars inundated an area over 2 km2 (0.78 mi2) and formed a debris fan that extended 3.6 km (2.2 mi) from the base of the volcano into Pavlof Bay [see fig. 35 in original text].�

Start Date: 01.2001 Eruption is UNCERTAIN Volcanic Explosivity Index (VEI): 1 Eruptive Characteristics: Central vent eruption Hydrothermal activity Steam McGimsey and others (2004) summarize 2001 steaming and other activity at Pavlof as follows: “Principal/Teacher, John Concilius, has a good view of Pavlof from his home in Nelson Lagoon. On January 20, 2001 he observed through binoculars steaming from multiple locations near the summit, but none actually at the top of the volcano. He re-

ported that the steam was white and not discolored, and, that the snow near the summit was clean with no evidence of melting. “He concluded by stating that this was the most steaming he had seen at the volcano during the past several years and that other villagers considered the steaming to be unusual.AVO remote sensing specialist Dave Schneider analyzed Advanced Very High Resolution Radiometer (AVHRR) satellite images taken from January 18 to 22, 2001 and found no evidence of increased thermal activity at the volcano and no unusual seismicity was noted.

No further reports of steaming were forthcoming.

This may have been a meteorological phenomenon.

While working in Cold Bay in early June, Martin

LaFevers, Seismic Data Manager at UAFGI, observed and photographed the summit of Pavlof during a weather break; it appeared to be covered with ash. A local pilot reported seeing ‘something other than steam’ at the summit. Again, there was no indication of anomalous seismicity.

Start Date: 09.11.1996 Stop Date: 01.03.1997 Dating Technique: Historical Records Volcanic Explosivity Index (VEI): 2 Eruptive Characteristics: Central vent eruption Explosive eruption Lava flow(s) Mudflow(s) (lahars) “Pavlof Volcano, historically the most active volcano in the Wrangell-Aleutian volcanic arc, began a

vigorous strombolian eruption in mid-September, 1996 (Neal, 1996). The eruption, which continued into early 1997, occurred only two months after a 6-station seismic network was established near the volcano. “A NWS observer in Cold Bay noted steam and incandescent ejecta above the volcano at about 0830 ADT on September 16. Analysis of seismic data and NOAA-12 and -14 AVHRR satellite images suggest that the eruption likely began at a very low level by September 11. Over the next few weeks, nearby residents observed intermittent strombolian eruptions from near the summit of the volcano. Pilots reported incandescent bombs the size of pick up trucks accompanied by minor ash clouds alternating with steam plumes rising from a few hundred meters to

approximately 2 km above the volcano. “Photographs from overflights on September 23 and AVO video from September 27-30 showed lava fountains emanating from two vents (figs. 4A and 4B). One vent was located on the east edge of an ~150-m diameter crater that indented the northwest summit of the volcano. A second, more active locus of fountaining was perched on the west edge of this crater 100-150 m below the summit. The two loci of fountaining were about 100 m apart and were generally not synchronous in activity. The east vent was less vigorous overall, producing intermittent puffs of gray to dark gray ash and steam tens of meters high. The west vent was the source of intermittent bursts of incandescent spatter up to 300 m high.

“By September 23, a small spatter cone was forming at the west vent and a collar of spatter, spatter-fed flows, and small lahars extended about 500 meters down the ~30 degree northwest flank below the summit crater. A lava flow formed by the coalescence and remobilization of heavy spatterfall and direct spill over from the west vent plunged down the steep flank, melting a narrow channel through seasonal snow and glacial ice. By September 29, the lava flow had reached the base of the cone, about 3.5 km from its source, and was beginning to widen into a lobate fan. Dark lahar deposits extended beyond the toe of this lava flow across the gently sloping ground northwest of the volcano, coming within about 40 m of AVO’s seismic station PV6.

By late October, a second lava flow issued from the east vent and on December 2, when videotaped by

Alaska State Troopers, this flow was the more active of the two and had nearly reached the base of the cone in the saddle between Pavlof and Pavlof Sister. “Eruptive activity became intermittent during the month of December. Seismicity decreased abruptly early on December 4 and ash was not visible above the regional cloud cover that obscured the summit of Pavlof for several days. Brief episodes of heightened seismicity occurred on December 10 (accompanied by at least one pilot report of ash) and December 27. The last reliable observation of ash emission occurred on January 3, although pilots and observers in Cold Bay reported possible minor ash in the steam plume over the volcano on a few occasions through February 6. Collapse of unstable agglutinate and hot fragmental debris on the steep

upper cone may well account for some of these small ash plumes. “During the first two weeks of the eruption, occasional elongate clouds containing minor amounts of ash were detected on NOAA AVHRR satellite images. During the third week, both pilot reports and satellite image analysis documented larger but still diffuse ash clouds trailing as far as 175 km downwind, but they rarely reached more than ~6 km above the sea level. These clouds varied in length from a few tens to several hundred km and were observed intermittently, weather permitting, through late December. On November 4, accompanying some of the strongest seismicity of the eruption, a plume was visible in Bands 4-5 extending 350 km northeast of the volcano.

“In addition to elongate plumes, thermal anomalies associated with high temperature material were also recorded near the volcano’s active vents and along the two main lava flow paths. The number of saturated pixels on AVHRR images varied from 1 15 indicating areas of up to about 18 km2 above 37 degrees C (A.L. Roach, oral communication, 1997).

The last significant thermal anomaly was recorded in late December, however “warm” pixels were noted during daily analysis of AVHRR data into mid-February. Pilot reports and observations from Cold Bay confirm continued warm ground around the summit of the volcano as inferred from areas of snow-melt.

“As in the 1986 eruption, the 1996 activity produced rubbly, fragmental lava flows that extend in two main lobes down the northwest flank of the volcano. Early in the eruption, these flows occupied, at least in part, channels cut into the seasonal snow and glacial ice on the volcano’s flank. Melting of this snow and ice produced water and rock mixtures of unknown consistency that flowed out onto the more gently sloping terrain northwest (and possibly northeast) of the volcano. As of this writing, we do not know how far these lahars traveled or what impact they had on the Cathedral River and other drainages around Pavlof.

“Very light ashfall was reported in King Cove on the night of October 5-6, Sand Point on October 19, and Nelson Lagoon on October 28.”

More from Neal and McGimsey (1997): “On October 3, based on observed plume heights, the FAA issued a Notice to Airmen (NOTAM) restricting flight below ~7 km and within 10 nautical miles of Pavlof.

Higher levels of seismicity and more energetic ash plumes began on October 15 and in response, the FAA increased the altitude of restricted air space to approximately 8 km and the size of the restricted zone to a 25 mile radius around Pavlof. The FAA continued to enforce this restriction until January 27, 1997. Although Pavlof ash plumes reached altitudes of 30,000 feet or more on a few occasions, there were no serious disruptions in the North Pacific airways. “There were, however, impacts on local air traffic. On November 4, a United States Coast Guard

(USCG) C-130 operating at low level over the Bering Sea was struck by lightning. The flight crew also reported a “smoky” smell in the cockpit and a fine dust throughout the plane. Subsequent discussion with the USCG failed to positively identify the source of this material. However, based on NWS forecast winds during the time of this report, it appears unlikely that primary ejecta from Pavlof could have been the culprit; rather, it is possible that low level winds remobilized fine ash from the ground.

No sample of the material was recovered for analysis.

“On November 27, 1996, a Reeve Aleutian Airways flight aborted landing into Sand Point when the pilot detected a brown haze that he interpreted to be ash from Pavlof.”

Start Date: 01.05.1990 Stop Date: 03.05.1990 Dating Technique: Historical Records Volcanic Explosivity Index (VEI): 2 Eruptive Characteristics: Central vent eruption Explosive eruption “Pavlof Volcano has been quiet since August 1988.

On January 5 and 6, 1990, Marsha Brown of the FAA flight service at Cold Bay observed traces of steam rising up to 100 m above the NE summit vent that was trailing to the NE. The top of the volcano was dark due to the melting of snow around the summit vent. The volcano has been pure white with snow for the winter up to this time. On March 5, several eruption plumes were observed.�

Start Date: 04.16.1986 Stop Date: 08.13.1988 Dating Technique: Historical Records Volcanic Explosivity Index (VEI): 3 Lava Volume: 7.8 x 106 m3 Area of Activity: NE & SE summit vents & flanks Eruptive Characteristics: Central vent eruption Flank (excentric) vent Explosive eruption Pyroclastic flow(s) Lava flow(s) Mudflow(s) (lahars) “The visual observations of the 1986 eruptions, both aerial and on the ground, provide information generally lacking from previous historic eruptions.

The physical characteristics of of the 1986 eruption are probably similar to other historic summit erup-

tions, although the 1986 activity was more explosive and of longer duration. “The 1986 activity was chiefly Strombolian, characterized by sporadic emissions of dark ash to heights of up to 5 km; one exceptionally strong (probably Vulcanian) eruptive event sent an ash column to over 15 km on 18-19 April. The initial phase of the eruption appears to have involved the summit vent on the north side of the volcano which has been the site of all Pavlof eruptions since the mid-1960s.

This eruptive phase lasted from 16 to 26 April and included a hot rootless agglutinate flow that extended down the northwest flank of the volcano. The deposit was actively degassing steam along its entire length in late June. It had an estimated volume

of about 4x10^6 cubic meters and, at an elevation of 760 meters, was 20-30 meters thick and 40-50 meters wide. The deposit was clast-supported and fines-depleted, consisting entirely of glassy, slightly vesicular andesitic basalt (SiO2 = 53.5%) bombs and irregular masses of spatter with a maximum diameter of about 1.2 meters. It was probably emplaced during the initial and relatively violent vent-clearing phases of the eruption on 16-28 April. Associated hot lahars caused melting of snow and ice and extensive flooding in the Cathedral River drainage north of the volcano. Heavy ash fall occurred north and west of the volcano during the April activity; 2-3 mm of ash fell on the nearby communities of Cold Bay, 35 km to the west, and King Cove, 48 km to the southwest, but caused no damage.

“Eruptive activity began again in late May and was highlighted by sporadic, but vigorous Strombolian eruptive activity and by the formation of a new vent high on the east flank of the volcano. Comparison of aerial photography indicated that this is the first major change in the vent geometry of Pavlof since the early 1960s. The period of activity was characterized by repeated small bursts of ash and cinder to a few hundred meters above the vent and spatter tossed a few tens of meters all accompanied by explosive, thunderlike reports. The explosions characterizing the Strombolian eruption occurred at intervals of 5-15 seconds during the half dozen times the new vent was observed between 14 June and 30 June, suggesting a moderately rapid rate of magma

rise in the conduit. Only minor ash emission was observed associated with the explosive ejection of incandescent bombs from the new vent. Activity from the old north vent during this time consisted of steam emission with little or no ash. “Close airborne examination of the new vent on 15 June revealed that a steep-sided, asymmetrical spatter rampart, 50-75 m across, had been constructed on the east, or downslope, side of the vent. A steep chute, directly below the spatter rampart, contained a steaming, rootless rubble flow. Further down the volcano at an elevation of about 750 m, this flow was about 100 m wide and consisted of bread-crustlike bombs and irregular masses of lava and spatter, up to 4 m in diameter, in an ash-rich, moderately

inflated matrix (in contrast to the flow on the northwest flank). It was actively degassing, exhibiting abundant steam fumaroles and occasional phreatic eruptions. The flow, with an estimated volume of 3.8 x 10^6 cubic meters, also generated a number of mudflows that continued downslope to about 600 m where the rubble flow-mudflow complex widened into three broad lobes. Below this elevation, debris-laden water from the flows was contained in a steep-sided small canyon. “The nature of the material in the flow at this elevation and the physical characteristics of the spatter rampart at the vent strongly suggest that much of the lower part of the flow may have resulted from similar pyroclastic flow activity following par-

tial collapse of the oversteepened spatter rampart.

Throughout the course of the eruption, the steep spatter rampart may have periodically become unstable and collapsed, either in whole or part, forming hot, disaggregated pyroclastic flows cascading down the chute. Where ice and snow were overrun by the hot debris, mudflows were generated that continued to travel down and fan out on the volcano’s lower slopes. In support of this hypothesis, a pyroclastic flow was observed on 19 June moving down the same chute from about 1400 m elevation to about 900 m; the upper 1100 m of the volcano was cloud-covered at this time.

An alternative scenario is that the pyroclastic flow observed on 19 June resulted from a ‘boil-over’ of the magma column at the vent following a larg-

er-than-usual explosion. Although no seismic evidence for such an explosion was observed, the obscuring cloud cover prevents an exact explanation for the origin o fthe observed pyroclastic flow.

The April-August eruption is similar to, but somewhat stronger than most of the other Pavlof eruptions of this century (Simkin et al., 1981; McNutt 1987a) in terms of its Strombolian character. The duration of the eruption, as indicated by lava fountain activity and spatter ejection, however, appeared to be much longer than for most modern eruptions.

This eruption also altered the physiography of the summit area by forming a new vent. In contrast to most recent eruptions (i.e., 1973-1983) that occurred in the fall of the year, the 1986 eruption was concentrated in the spring and summer.�

McNutt and others (1991) also give detailed information about the seismological data collected during this eruption.

Information on the continuing volcanic activity in 1987 and 1988 is in other sources. From Reeder (1990, pg. 53): “Numerous observations of tephra and steam emissions were made during most of 1987 from NE and SE near summit vents and less from a NE flank vent. Lava flows occurred on both the NE flank and the SE flank of the volcano from the summit vents down to at least a 1,000 m a.s.l. elevation in January and February, form the NE summit vent in May and June, and again from both summit vents in August.” Please see the rest of this text for detailed eruption observations in 1987.

From Reeder (1991): “Pavlof volcano has been fairly

active during 1986 and 1987 with tephra and lava emissions occurring form several summit and flank vents. During 1988, eruptive activity was restricted to only small tephra and steam emissions from NE near summit vent up through August 13, except for one minor steam emission from a NE flank vent on March 2. Since August 13, 1988, no eruptive activity was observed for the rest of the year.�

Start Date: 11.11.1983 Stop Date: 12.181983 Dating Technique: Historical Records Volcanic Explosivity Index (VEI): 3 Tephra Volume: > 1.3 Âą 0.4 x 107 m3 Area of Activity: Upper NE flank Eruptive Characteristics: “Eruptive activity was first observed from Sand Point (about 90 km E of the volcano) late on 14 November and pilots observed tephra columns the next afternoon. On 19 November a small vapor cloud rose approximately a hundred meters above the vent. Bad weather prevented observations until 26 November when Pavlof was visible until mid-afternoon from Cold Bay (about 60 km SW of the volcano). During the morning, a vapor plume containing a little ash rose to 4.5 km altitude. At intervals of approximately 30 minutes, puffs of dark ash were emitted. The intervals became short-

er, and by 1500 ash emission was nearly continuous. “Through October and early November, a Lamont-Doherty seismic monitoring station near the volcano recorded background levels of 0-40 (usually 0-30) small low-frequency events per day. A 30-minute burst of volcanic tremor began at 2000 on 4 November, and a 6-minute burst at 1757 on 9 November. Between 1430 on 11 November and 1100 on 13 November, 15 explosions were recorded.

Several bursts of tremor of 1-2 minute duration occurred between 1700 and 1900, when continuous tremor started. Its amplitude gradually increased, and tremor began to saturate the seismograph at 1100 on 14 November. Tremor was strongest between midnight and 1200 on 15 November, and continued to saturate the seismograph until 2100 on 15 November when its amplitude began to decrease. Tremor remained continuous but at

low amplitude between 1300 on 16 November and 1200 on 18 November. Intermittent low-amplitude tremor and numerous low-frequency (B-type) events recorded after 1200 on 18 November were continuing on 21 November. “Airline pilots last reported eruption clouds from Pavlof at 1400 on 15 December and there have been no eyewitness reports of eruptive activity since then. Six explosions were recorded between 1600 and 2000 on 15 December by Lamont-Doherty’s 5-station seismic net 4.5 - 10 km from the volcano. One of these stations, about 7.5 km from Pavlof, detected bursts of harmonic tremor 17 December, 1100 - 18 December, 0330; 18 December, 0530 - 0615 and 1040-1110; 20 December, 2200 - 2245; and 21 December, 2035 - 2048.

Seismicity then decreased to the background level of several tens of events per day and remained at that level as of 26 January.

Eruption plumes were observed on 3 images returned 15-17 December from the NOAA 8 polar orbiting satellite. The images returned at 2101 on the 15th and 1031 on the 17th showed well-defined, relatively dense plumes extending 225 km E and 400 km NE from Pavlof above the weather cloud layer. A diffuse plume was observed on the image returned at 2108 on 18 December. “No volcanic plumes were observed on other images returned 15-21 December, but heavy weather clouds obscured the area.�

Other Eruptions & Activity 1982 Jul 15, 1981 Sep 25, 1980 Nov 8, 1980 Jul 6 ,1975 Sep 13, 1974 Sep 1, 1974 Mar 12, 1973 Nov 12, 1966 Mar 15 1958 May 17, 1953 Nov 25, 1951 Oct 3, 1950 Jul 31, 1936 - 1948, 1929 Mar 1, 1924 Jan 17, 1922 Dec 24, 1914 Jul 6, 1906 - 1911, 1901, 1894, 1892, 1880, 1866 Mar 14 ,1852, 1846 Aug 15 “The mountain burst with a loud ‘cannonade’ at this site [eastern slope of the mountain, where a pre-existing lava flow was] in August, 1846. Smoke poured out in clouds from a fissure, ash fell, and flames appeared. Flames also shot up from the summit. A northwest wind dispersed both the smoke and the ash that obscured from the inhabitants of Pavlof the islands at the mouth of the bay.

The ash was carried to the village of Pavlof, where it was necessary to place a covering over the fish that were hung up. Smoke and ash were carried to Unga Island (about 85 kilometers to the east), where people also protected drying fish from ash by covering it with matting.”

Culture Pavlof Volcano The main challenge of climbing this peak is its remoteness and the consequent difficulty of access.

The peak is a 30 mi journey from the north side of Cold Bay. The climb itself is a straightforward snow climb, and the ski descent is recommended The volcano is below the path of hundreds of daily international flight paths, and an explosive eruption could interrupt those operations, said Steve McNutt, a volcano seismologist with the observatory. Volcanic ash can enter an engine and make it seize up, he said.

Pavlof Bay is an inlet in Alaska located on the southwestern edge of the Alaska Peninsula. It is on the peninsula’s south coast, is about 50 miles (80 kilometers) long, and lies directly north of the Pavlof Is-

lands. The 8,261-foot (2,518-meter) volcano Mount Pavlof is on its western shore Pavlof is about nine miles from Pavlof Bay, a popular fishing ground. Pavlof Bay, on the southern side of the Alaska Peninsula, supported one of the world’s largest pandalid shrimp fisheries until 1979, and about 70% of the catches consisted of the northern shrimp The English name for the island comes from Pitka Pavalof, a Creole of Russian-Native. In 1893, Pitka Pavalof and Sergei Gologoff Cherosky, Creoles of Russian-Native descent, found gold on Birch Creek in Interior Alaska. Learning of the discovery, prospectors jumped their claims and argued that the claims were invalid because the men were Natives. The discovery attracted more non-Natives to the Yukon River and the town of Circle was founded are a group of culturally similar indigenous peoples inhabiting the Arctic regions of Greenland, Canada, the United States, and Russia. Inuit is a plural noun; the singular

is Inuk. The Inuit languages are classified in the Eskimo-Aleut family.

In the United States, the term Eskimo is commonly used in reference to these groups, because it includes both of Alaska’s Yupik and Inupiat peoples while “Inuit” is not proper or accepted as a term for the Inupiat. No collective term exists for both peoples other than “Eskimo”. However, natives in Canada and Greenland view the name as pejorative and “Inuit” has become more common. In the United States, Inupiat live on the North Slope in Alaska and on Little Diomede Island. In Russia, they live on Big Diomede Island. The Greenlandic Inuit are the descendants of migrations from Canada and are citizens of Denmark, although not of the European Union.