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Transcript of Vulcan AlaskaEdition
Akutan Peak
Elevation:4275 ft Latitude:54.13308° NLongitude:165.98555° W
Official Name: Akutan PeakType: Stratovolcano with calderaLatest Activity: 12.18.1992 Seismically Monitored:Yes
Akutan is one of the most volcanically active islands in the eastern Aleutian arc.
TYPE:
From Miller and others
(1998): “Akutan volcano is
a composite stratovolcano
with a circular summit cal-
dera 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 max-
imum 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, ex-
tends 1.5 km southwest of
Akutan Peak and is termi-
nated to the north by the
younger caldera. Small gla-
ciers fill the older crater and
lie within the southwest and
southeast margins of the
younger caldera.
“The active intracaldera cin-
der cone is over 200 m high,
about 1 km in diameter, and
located in the northeast quar-
ter 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 obliter-
ated by more recent activity.
Both lakes drained to the
north through a gap in the
caldera wall.
DefintionsCaldera
Pleistocene Age
A caldera is a large, usually circular depression at the summit of a volcano formed when magma is with-drawn 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.
The most recent episode of glaciation, the Pleisto-cene 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 advanc-es 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 pyro-
clastic 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 erup-
tion 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 ex-
truded in 1947 blanket the
central portion of the north-
west 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 depos-
its . 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 de-
grees 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 Har-
bor 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 gen-
erate 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 us-
ing 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 re-
cently 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 earth-
quake was magnitude 5.1. On 13th March, felt-earth-
quakes 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 EruptionsSmall steam and ash eruption occurred at Akutan
volcano in April and December 1992.
1991 EruptionsSummit ash emissions began in September, with a
plume to 4500 m altitude. Ashfall was reporded at
Akutan village.
1990 EruptionsSmall ash eruptions were reported in September
and October. Maximum height of plumes were
1500 m above the summit.
1989 EruptionsIn March 1989 an air shock wave was felt by a
pilot flying over the western shore of Akutan vol-
cano. Black ash was emitted to a height of 2,300 m
above the volcano.
1988 EruptionsAsh emissions occurred at Akutan volcano be-
tween March and June 1988. Most observations
were by pilots.
1987 EruptionsOn 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 EruptionsIn June, numerous ash emissions to an altitude of
3.5 km were visible from Akutan village.
1980 EruptionsOn the 3rd July a recent lava flow that had moved
through a breach in the NNW caldera wall was
observed.
1978 EruptionIn 1978 lava flowed through a gap in the calde-
ra and came within 1 km of the sea in the north.
Strombolian eruptions occurred at the summit.
1977 EruptionsEruptions began in May, with light brown ash
emissions every 15 minutes. Incandescence was
noted in some eruptions.
1974 EruptionsIn February, ash was emitted hundreds of feet into
the air, and lava flowed down the flank.
1973 EruptionsAkutan volcano erupted ash and steam for several
months, with the mountain snow-free.
1946-48 Eruptions 1946-48 EruptionsLava flows occurred at the volcano caldera.
1924 EruptionA lava flow occurred on the floor of the caldera.
Eruptions in the 1850’sA 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 Eruptions1912, 1911, 1908, 1907, 1896, 1892, 1887, 1883, 1867, 1865, 1852, 1848, 1845, 1838, 1790
Akutan Summit and Intra Caldera
July 2003. Jeff Wynn
CultureAkutan 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 Aku-tan 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 ex-ists 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 be-gan 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 commer-cial fishing permits. Subsistence hunting and fish-ing activities are minimal because the majority of residents are employed. The majority of the popula-tion lives in group quarters facilities.TransportationBoats and amphibious aircraft are the only means of transportation into Akutan. Cargo is delivered weekly by freighter from Seattle. Akutan has no air-strip, however, a seaplane base is available. Daily air service is available from nearby Unalaska.ClimateAkutan lies in the maritime climate zone. Tem-peratures range from 22 to 55. Precipitation averag-es 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 actu-ally 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 coun-try, 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, Aku-tan 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-es-tablish 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.
Kurt Schmidt participating in the rock toss.Wolfgang Brinck
Akutan Bay separtes the harbor from the Spring. While the volcano sits in the background.
Jeff WynnVolcanologist set up equiptment near Akutan’s hot springs.
Akutan Village
Jeff Wynn
Akutan Canary
Elevation: 8261 ft Latitude: 55.4173° NLongitude: 161.8937° W
Official Name:Pavlof VolcanoType:StratovolcanoLatest Activity: August 15, 2007Seismically Monitored: Yes
The most active volcano of the Aleutian arc
Pavlof Volcano
Type:
Pavlof is a composite cone
volcano located in the south-
western region of Alaska
about 600 kilometers south-
west of Anchorage. At its
summit Pavlof reaches an
elevation of 8,262 ft (2518).
The volcano consists of an-
destic 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 ac-
tivity, mudflows, and flood-
ing 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 ac-
tivity is always present. For-
tunately the volcano is locat-
ed 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 oth-
ers, 1991). It is situated high
on the northeastern flank
of Emmons Lake caldera
along a northeast-trending
alignment of vents that in-
cludes Little Pavlof, Pavlof
Sister, and several intracal-
dera cones (Kennedy and
Waldron, 1955). The com-
posite volcano is relatively
undissected and is probably
Holocene in age. Pavlof lies
within the Shumagin seis-
mic gap (Davies and others,
1981).
Volcanic activity
Mount Pavlof is the most
active volcano in the Aleu-
tian volcanic arc with al-
most 40 relatively well-doc-
umented eruptions dating
back to 1790 (Newhall and
Dzurisin, 1988; Smithso-
nian Institution, 1976-1988;
McNutt, 1987; Coats, 1950;
Jaggar, 1932). It is so consis-
tently active that a question
sometimes arises as to what
constitutes a separate erup-
tion. 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 ema-
nate from the summit vents
on occasion. Short-lived vol-
atile-rich vulcanian ash col-
umns 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 phreatomag-
matic and McNutt (1987)
found a correlation between
seismic activity and type of
eruption. Strong volcanic
tremor accompanied ma-
jor Strombolian magmatic
eruptions, whereas episodes
of explosion quakes, with
little to no volcanic tremor,
were diagnostic of minor
phreatomagmatic events.
The largest historical erup-
tion of Pavlof occurred on
December 6-7, 1911 at the
end of a five year period of ac-
tivity. 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 pe-
riod began mid-April, 1986
and continued through Au-
gust, 1988 (Smithsonian In-
stitution, 1986-88; McNutt
and others, 1991). Frequent
steam and ash emission, ex-
plosions, and strong tremors
accompanied summit lava
fountaining that fed sev-
eral agglutinate lava flows,
which in turn produced a
number of both hot
and cold, extensive mud-
flows.During the early course
of the eruption, the eruptive
vent shifted from the north
to the east side of the sum-
mit. The most recent erup-
tive episode at Mount Pavlof
began about September 11,
1996 and continued into
early 1997 (Neal and Mc-
Gimsey, 1997). The erup-
tive activity was strombolian
in character and similar to
most Pavlof eruptions. In-
termittent explosive activity
and lava fountaining were
recorded from two close-
ly-spaced vents high on the
northwest summit of the
volcano. Incandescent spat-
ter, 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 max-
imum of 10 kilometers
above sea level (generally
less than 6 kilometers) and
extended up to several hun-
dred kilometers downwind
were detected on satellite
images and reported by pi-
lots. These clouds consist-
ed 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 com-
posed of basaltic andesite
flows and pyroclastic rocks
that overlap similar rocks
from nearby Little Pavlof.
The flows are moderately
phyric with about 25% phe-
nocrysts, mostly plagioclase
with minor olivine and clin-
opyroxene. The agglutinate
flows of 1987 are of similar
andesitic composition.
Volcano Structure: The vol-
cano is 7km in diameter and
has two active vents, one lo-
cated on the northern side
and the other on the eastern
side (Miller et al, 1998) and
the overall outline of the vol-
cano 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 & Deck-
er, 1998) with the latest
eruption occurring from
September 1996 to January
1997 (Wallace et al, 2000).
The type of eruptions nor-
mally seen from Pavlof
consist of Strombolian and
Vulcanian eruptions where
the main components are
bombs and ash that normal-
ly reach heights of around
200 to 300m (Miller et al,
1998).
The largest eruption in Pav-
lof’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 to-
gether with lava flows and
also lava fountains.
Eruptions and Activity
Start Date: 08.15.2007 Stop Date: 09.13.2007 Dating Technique: Historical RecordsVolcanic Explosivity Index (VEI): 2Eruptive 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 seis-mic 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 an-
nounced that an eruption was expected. With the
upgrade in color code, AVO began 24-hour surveil-
lance 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 ther-
mal 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 in-
dicated 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 20-
to 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 be-
gan waxing and waning for the first week of Sep-
tember. A strong TA was present in satellite imag-
es, 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 de-
creased 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 ac-
tivity had ceased during their visit on September 19,
and the Aviation Color Code /Volcano Alert Level
was downgraded to YELLOW/ADVISORY on Sep-
tember 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 alti-
tudes 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 de-
tected 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
′m). Although no visible ash fallout was observed
during aerosol sampling, these results demonstrate
that volcanic ash was present in respirable size frac-
tions downwind of the volcano even during periods
of low ash emissions (Peter Rinkleff and Cathy Ca-
hill, AVO/UAFGI, written commun., 2010).
“Analyzed samples from the lava flow are basaltic
andesite in composition (53% SiO2), which is sim-
ilar 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 consid-
ered the steaming to be unusual.AVO remote sens-
ing specialist Dave Schneider analyzed Advanced
Very High Resolution Radiometer (AVHRR) satel-
lite 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, ob-
served 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: 09.11.1996Stop Date: 01.03.1997Dating Technique: Historical RecordsVolcanic Explosivity Index (VEI): 2Eruptive Characteristics: Central vent eruption Explosive eruption Lava flow(s) Mudflow(s) (lahars)
“Pavlof Volcano, historically the most active volca-
no 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 in-
candescent 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 res-
idents observed intermittent strombolian eruptions
from near the summit of the volcano. Pilots report-
ed 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 gen-
erally 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 form-
ing at the west vent and a collar of spatter, spat-
ter-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 coales-
cence 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 wid-
en 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 abrupt-
ly 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, occa-
sional elongate clouds containing minor amounts
of ash were detected on NOAA AVHRR satellite im-
ages. During the third week, both pilot reports and
satellite image analysis documented larger but still
diffuse ash clouds trailing as far as 175 km down-
wind, 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 ob-
served 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 anoma-
lies 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 record-
ed 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 pro-
duced rubbly, fragmental lava flows that extend in
two main lobes down the northwest flank of the
volcano. Early in the eruption, these flows occu-
pied, 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 mix-
tures of unknown consistency that flowed out onto
the more gently sloping terrain northwest (and pos-
sibly 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 Octo-
ber 3, based on observed plume heights, the FAA is-
sued 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 al-
titudes of 30,000 feet or more on a few occasions,
there were no serious disruptions in the North Pa-
cific airways.
“There were, however, impacts on local air traf-
fic. On November 4, a United States Coast Guard
(USCG) C-130 operating at low level over the Ber-
ing Sea was struck by lightning. The flight crew
also reported a “smoky” smell in the cockpit and a
fine dust throughout the plane. Subsequent discus-
sion 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 ap-
pears 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 analy-
sis.
“On November 27, 1996, a Reeve Aleutian Airways
flight aborted landing into Sand Point when the pi-
lot detected a brown haze that he interpreted to be
ash from Pavlof.”
Start Date: 01.05.1990 Stop Date: 03.05.1990Dating Technique: Historical RecordsVolcanic Explosivity Index (VEI): 2Eruptive 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 vol-
cano 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 RecordsVolcanic Explosivity Index (VEI): 3Lava Volume: 7.8 x 106 m3Area of Activity: NE & SE summit vents & flanksEruptive 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 explo-
sive and of longer duration.
“The 1986 activity was chiefly Strombolian, charac-
terized 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 extend-
ed down the northwest flank of the volcano. The
deposit was actively degassing steam along its en-
tire 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 diam-
eter of about 1.2 meters. It was probably emplaced
during the initial and relatively violent vent-clear-
ing phases of the eruption on 16-28 April. Associ-
ated 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 charac-
terized 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 ex-
plosive, thunderlike reports. The explosions char-
acterizing the Strombolian eruption occurred at in-
tervals 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 spat-
ter 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-crust-
like 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 north-
west 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 wid-
ened 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 ele-
vation and the physical characteristics of the spat-
ter 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 un-
stable and collapsed, either in whole or part, form-
ing 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 volca-
no’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 evi-
dence for such an explosion was observed, the ob-
scuring cloud cover prevents an exact explanation
for the origin o fthe observed pyroclastic flow.
The April-August eruption is similar to, but some-
what stronger than most of the other Pavlof erup-
tions of this century (Simkin et al., 1981; McNutt
1987a) in terms of its Strombolian character. The
duration of the eruption, as indicated by lava foun-
tain 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 oc-
curred in the fall of the year, the 1986 eruption was
concentrated in the spring and summer.”
McNutt and others (1991) also give detailed in-
formation 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 RecordsVolcanic Explosivity Index (VEI): 3Tephra Volume: > 1.3 ± 0.4 x 107 m3Area of Activity: Upper NE flankEruptive 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 continu-ous.
“Through October and early November, a Lam-ont-Doherty seismic monitoring station near the volcano recorded background levels of 0-40 (usu-ally 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 oc-curred 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-ampli-tude 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 be-tween 1600 and 2000 on 15 December by Lam-ont-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 Decem-ber, 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 im-ages returned 15-21 December, but heavy weather clouds obscured the area.”
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 in-habitants 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.”
Other Eruptions & Activity
CulturePavlof Volcano
The main challenge of climbing this peak is its re-moteness 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 erup-tion could interrupt those operations, said Steve McNutt, a volcano seismologist with the observato-ry. Volcanic ash can enter an engine and make it seize up, he said.
Pavlof Bay is an inlet in Alaska located on the south-western edge of the Alaska Peninsula. It is on the peninsula’s south coast, is about 50 miles (80 kilo-meters) long, and lies directly north of the Pavlof Is-
lands. The 8,261-foot (2,518-meter) volcano Mount Pavlof is on its western shorePavlof is about nine miles from Pavlof Bay, a popular fish-ing ground. Pavlof Bay, on the southern side of the Alaska Peninsula, supported one of the world’slargest 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 Ser-gei Gologoff Cherosky, Creoles of Russian-Native descent, found gold on Birch Creek in Interior Alaska. Learning of the discovery, prospectors jumped their claims and ar-gued 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 inhabit-ing 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 Eski-mo-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”. How-ever, 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 descen-dants of migrations from Canada and are citizens of Den-mark, although not of the European Union.