What type of volcano is augustine

Kienle, J. Johnston , H. Schmincke , J. Kienle , and M. Utting , Univ. Juergen Kienle reports that seismicity at Augustine began to increase last summer for the first time since , when the volcano last erupted. Between 12 July and 7 August, approximately shallow microearthquakes were recorded each day on Augustine's network of four seismic stations. An intense peak occurred on 22 February between and , when 70 microearthquakes were recorded on the seismometer less than 1 km from the dome, 2 hours before USGS scientists flew over the volcano and reported active degassing see below.

These microearthquakes were all shallow and indicate fracturing and degassing of the dome. The following is a report from M. The plume rose to an estimated altitude of more than 3 km.

Seismic recorders at the USGS office in Anchorage, which monitor some of the University of Alaska Geophysical Institute seismometers, had shown an increase in small events near Augustine, beginning 13 February. On 20 and 21 February, the USGS began receiving reports from observers in Homer km NE of Augustine and from pilots flying near the volcano that it was vigorously steaming. The main fumarolic vent was in the moat E of the dome.

During the observations between and , fumarolic activity was continuous and steady. The plume was whitish, with a few grayish wisps. The SE and W sectors of the snow-covered cone were lightly dusted with ash, believed to be comminuted portions of the dome.

No sign of avalanches or falling blocks from the dome were observed. During a 28 February overflight, USGS personnel noted an increase in the amount and area of fumarolic activity compared to 22 February. Augustine may be following its traditional pattern of slowly forcing the summit dome up followed by dome destruction and pyroclastic flow activity. No plume had been visible on 13 March, and clouds obscured the area March.

Yount , T. Strong explosions send clouds to A series of powerful explosions March sent eruption clouds into the stratosphere and generated pyroclastic flows that reached the sea.

Ash was deposited over a wide area and international air traffic was disrupted. Yount reports that "Augustine began to erupt during the early morning of 27 March. Observers in fishing boats 55 km SE of the volcano and ashore in Homer, km ENE, reported 'orange flashes' of light and 'smoke and fire' from the volcano between and The leading edge of the main plume moved up the E side of Cook Inlet, depositing an estimated 1.

Numerous major eruptive events with column heights estimated at 9. Major bursts were recorded at , , , and During 27 March several lahars were generated on the S flank of the volcano, and pyroclastic flow activity was reported.

Pyroclastic flows down the N flank. Most were of insufficient volume or speed to reach the sea. On 29 and 30 March, a continuous eruptive plume with varying ash content rose to elevations of During periods of high plume ash content, pyroclastic flows were spilling from the summit vent area at a rate of one every minutes figure 3. As before, most did not reach the sea. This burst was accompanied by large pyroclastic flows which entered the sea on both sides of the University of Alaska Geophysical Institute's Burr Point Cabin on the N side of the island generating billowing white plumes to 1.

Both seismicity and ash content of the plume tapered off after 31 March. On 29 March, a Sabena Airlines DC suffered significant abrasion of windshield and turbine parts while descending to Anchorage airport in near zero visibility conditions caused by ash in the atmosphere. Businesses and offices in Anchorage closed early on 27 March after requests from the utility company to curtail electrical usage because of potential shutdowns of turbine generators.

Postal service was disrupted. An air quality health alert was in effect on 28 March due to high particulate concentrations. Total SO 2 content was significant, but its magnitude has not yet been determined. Many images from the NOAA 6 and 9 polar orbiting weather satellites showed plumes, extending as much as km from Augustine.

NOAA scientists estimated possible plume heights by comparing radiosonde data on wind directions at various altitudes with directions of plume movement observed on satellite images table 1. Estimates ranged to 24 km, but elevations often could not be determined uniquely because of similar wind patterns at different altitudes. Infrared imagery generally showed a hot spot over the volcano, where heat saturated the temperature sensors. Table 1. Dimensions of plumes from Augustine, 27 March-6 April , derived from polar-orbiting weather satellite images.

Plume heights are estimated by comparing wind data collected at known altitudes by nearby radiosondes with observed directions of plume movement. Multiple altitude estimates are given when plume behavior correlated with similar wind patterns at more than one elevation.

On the 27th, the island's five seismic stations recorded intense high-frequency shallow seismicity. Superimposed pulses that saturated the instruments for several-minute periods were believed to be associated with eruptive bursts.

These occurred during periods of increased seismic intensity at island stations and were associated with reports of ash bursts. Seismicity continued with variable intensity over the next few days.

Seismometers on the N side of the island sensed more activity than those on the other flanks, presumably indicating passage of pyroclastic flows down that side of the volcano. On 31 March, a large seismic event, associated with the last major ash explosion, began at and lasted approximately 15 minutes. The signal contained three major pulses and had an average magnitude of 2. Seismicity was quiet for a day, then resumed briefly before ceasing to be recorded at seismometers 28 km away figure 6.

During the first week of April, poor weather conditions precluded systematic observation of the volcano, but continuous seismicity indicated that a continuous plume, carrying variable amounts of ash, was being emitted from the volcano. During an overflight on 2 April, pyroclastic flows were observed advancing down the N side of the volcano.

On 3 April an airplane pilot reported a plume to 3 km. During an overflight on 6 April, "boil-over" type pyroclastic flows were being emitted from the volcano.

During the same day, from separate aircraft, Juergen Kienle and USGS scientists were able to make their first good observation of the summit. They both noted that most of the dome was still intact, with some loss on the S side. There were no signs of a new dome. On 10 April, Kienle noted that: 1 A virtually continuous plume containing variable amounts of ash had been emitted from the summit since the eruption's onset.

Sampling on the island had been impossible, but fine brown ash appeared to cover the entire island. These data suggested to Kienle that only phreatic or phreatomagmatic activity had occurred, produced by dike injection to approximately sea level, where magma came into contact with the water table. Tom Gosink reports that preliminary chemical analysis of ash shows that low-sulfur, high-silica, andesitic material was ejected from the 28 March eruption table 2. The 2 April eruption was distinctly richer in silica, particularly the fine 3, up to 1, ppm, were measured, associated almost exclusively with the fine particles.

Lead was detected to only 10 ppm concentrations in all of the ash except the 2 April fine material, in which more than 80 ppm was measured. Table 2. Analyses of Augustine ash, by energy dispersive X-ray fluorescence at the University of Alaska, showing changes with time and particle size.

Yount and T. Matson , G. Stephens , and O. Krueger , GSFC. New lava dome in summit crater; details on pyroclastic flows and seismicity. Miller report that "A USGS overflight of Augustine on 24 April established the presence of new lava dome material in the moat between the remnants of the dome and the SW rim of the summit crater.

Hot blocks were spalling off the NW side of the new dome, avalanching down a gully on the W side of the dome. Small ash-rich fumaroles were active on the dome's entire N flank. During the flight, a burst of white vapor that lasted for several minutes appeared from the dome's NW base.

Observers on a night flight 24 April, using US Army night vision goggles, were able to see incandescent material all around the dome. Although the summit was obscured on 25 April, observers were able to see a blocky flow in the chute on the dome's E side. On 27 April it was apparent that the lava flow originated from the summit crater, draping the E side of the dome. Small pyroclastic flows were observed that day on the dome's NW side.

Samples collected on 28 April from the toe of the lava flow are silicic andesite, as are breadcrusted pumiceous material from the pyroclastic flows. Seismicity indicated that the dome was actively building between approximately 22 April and the late evening of 28 April, when the almost constant tremor abruptly died out.

Juergen Kienle reports that "After the strong explosive activity that began on 27 March and ended with a major explosion on 31 March at , the volcano was visited by helicopter on 19 and 28 April and 6 May. The following are preliminary results from those field investigations. Pyroclastic flows. March 31 was the only day on which pyroclastic flows entered the sea, 5 km from the vent.

A strong odor of Halogen gas Cl 2 , possibly F 2 , Br 2 was detected when crossing the still-steaming areas where flows had entered the sea. The flows were strongly inflated on 19 April, almost 3 weeks after emplacement. Driftwood on the beach was charred; one log was charcoaled, indicating that it had caught on fire. The NW flow lobe had buried a former fresh-water lake and a brackish-water swamp area. In that area we noted several small phreatic explosion craters, about 10 m in diameter.

There were rare banded pumices and occasional breadcrusted blocks. Individual flow units were about m thick. The bulk chemistry of one of the breadcrusted blocks is given in table 3 sample 4.

Table 3. Using 11 km 2 we obtain 0. Individual locatable earthquakes are now rarely recorded. Figure 8 shows a count of individual pyroclastic flows or rock avalanches 31 March May. The plot thus essentially shows periods of intense dome deformation.

Figure 9 shows one of the avalanches that would have been counted, descending the N flank of the volcano to about the m level. It was photographed from our N flank seismic station 2 km from the vent on 19 April at That station was damaged and a solar panel was incinerated by a hot blast associated with pyroclastic flow activity on 31 March. Parts of the installation protruding above ground antennas, masts, and solar panel were pockmarked with dents from flying rock.

Fortunately the buried electronics box and batteries were not damaged and the station has continued to operate uninterruptedly up to 10 May. Significant avalanche activity was observed 20 April May, a period of strong dome transformation. Figure 10 is a hypocentral cross section for events occurring 27 March April.

The plot shows that most earthquakes occurred in the upper 2 km of the volcano. Figure 11 is a digital playback for 3 individual events showing their great similarity.

We speculate that they are produced by meltwater contacting the central glowing conduit and flashing the water rhythmically to steam. On 6 May, Tom Miller thought that he could see puffing of the eruption column in spite of the strong winds that drove the plume down to the shore. He also noted that new snow had fallen and was melting. Dome growth. As of 6 May its height was m with a base diameter of m and a volume of about 0.

Its surface was blocky and spiny. An active vent was located in the SSW corner of the crater, a source of numerous boil-over pyroclastic flows. Slabs of glowing rock frequently spilled off the N face of the dome as seen by Kienle on 28 April. Five XRF chemical analyses of ejecta are listed in table 3. The bulk chemistry shows an interesting trend toward less silicic magma as the eruption proceeded.

Ballistic bombs collected on 19 April on the S flank near Bench Mark Kamishaki sample 3 and a breadcrust block sample 4 collected from the NE lobe of the pyroclastic flows are believed to have been ejected on 31 March. The high SiO 2 content The eruption of Augustine has thus far followed a quite different course from the eruption, which began with a violent vent-clearing phase, followed by a day repose, in turn followed by intrusion of a new dome. During the present eruption, a vent-clearing phase never occurred.

The pre-existing dome was slowly transformed into a new dome. March 31 was the only day of substantial production of highly vesiculated magma, ejected as large blocks on all flanks of the volcano but predominantly as pyroclastic flows down the N flank.

There are no sub-plinian pumice fall deposits on the island. A pathway for the vesiculating material was probably eroded out of the pre-existing conduit the dome on 31 March. This open conduit continues to produce occasional small-volume pyroclastic flows and was the source of the peculiar "percolator-like" seismicity described above, as meltwater interacted with new hot conduit rock.

The most remarkable feature of the eruption thus far is how well lithostatic pressure has confined the eruption, which was never particularly violent in spite of the fact that the beginning phase shows clear evidence of phreato-magmatic processes due to the interaction of ground water near sea level with the rising magma. If any of the pre-existing structures dome, dome, or dome had collapsed catastrophically, the unloading would have very likely produced much more violent activity.

Kienle , C. Rowe , J. Power , and L. Nye and J. Following the extrusion of its new dome between [23] and 28 April, activity at Augustine decreased rapidly. As of 7 June, a variable steam plume carrying small amounts of ash was still being emitted from the summit, occasionally to 3 km altitude. Scientists on the island 6 and 7 June noted an intense sulfur odor in the plume and a strong halogen smell on the pyroclastic flows.

As of 11 June, tens of individual earthquakes were being recorded daily by the seismometer on the N flank of the volcano, indicating brittle fracturing of the cooling dome.

Active degassing of Augustine continued following the major dome extrusion phase of April. During field studies from late June through mid-July, no major changes were noted in the morphology of the new dome, although slow dome growth appeared to be continuing as seen by occasional dome-collapse pyroclastic flows and incandescent rockfalls. Merapi-type pyroclastic flows extending km down the N flank were observed in late evening on 26 June, around noon 1 July, and at on 17 July.

Inspection of seismic records suggested that they occurred on other occasions as well. A coarse debris flow, m thick at its terminus, was observed on 2 July and was probably emplaced during a rainstorm the previous night. It stopped 2 km from the summit within the axial levees of the NW pyroclastic flow. Active fumaroles covered much of its surface, and incandescent cracks were observed. Intense fuming prevented ground observations of the dome while geologists were at the summit, but an overflight confirmed that the dome was emplaced within a crater in a remnant of the dome.

The top of the new dome was lower than the crescent-shaped remnant of the dome on the S side of the crater, and was roughly comparable to the elevation of the dome remnant on the NW side. The most vigorous fuming originated from vents in the moat between the new dome and a ramp below the dome. Fumarole condensates had a pH of between 0 and 0. Helens in December An adjacent hole showed isothermal convection at the boiling point for the upper 1. At press time continuous noise on seismic records from to on 20 August indicated that an explosive eruption had taken place.

The following is from Juergen Kienle. Renewed dome growth resulted in intense pyroclastic flow activity and plumes rose to 2,, m. Incandescent samples of a newly extruded spine were collected by Tom Miller and Kienle on 11 September.

The following is a summary of preliminary field observations. Observations from overflights and fishing boats. The onset of activity coincided with the full moon, the peak range of the fortnightly earth and ocean tides. Light brown dust was trailing SE to Cape Douglas, 50 km away. Other pilots reported plumes to m. That evening , the crew of a fishing boat NW of the volcano observed incandescent pyroclastic flows descending the northern flanks of the volcano.

At noon the next day, Tom Miller overflew the mountain and reported very modest ash emissions to a few hundred meters above the vent. Glow was seen from a fishing boat on 25 August.

Miller overflew the volcano again August, observing pyroclastic flows and small eruption clouds that rose to 1,, m above the volcano. The summit was partially obscured by orographic clouds. Earthquake activity had declined dramatically since the end of the major 27 March-early May eruptive phase. No buildup of seismicity preceded the present dome growth episode.

However, it should be noted that during periods of intense avalanching or pyroclastic flow activity, the seismic background noise is so high that we cannot recognize individual microearthquakes. Starting on August, we noticed a decided increase in surface events, with more than 50 events counted daily between 21 and 31 August. As of 13 September, the surface event activity had declined to the low summer background level.

On 28 August, the ash plume reached about 2, m and prevailing winds carried it to uninhabited areas NW of the volcano. The entire W, N, and E slopes were heavily covered with wet ash all the way to the beach. Leaves and wildflowers were wilted brown from heavy ash accumulation and passage of SO 2 clouds. During the day, we managed to observe many pyroclastic flows at close range; figure 16 shows one descending the N flank around noon.

Usually, pyroclastic flow activity followed intense rock avalanches high on the dome. Unfortunately, the dome was obscured by clouds and we could not see the rockfalls but they were distinctly audible. On one occasion, we clearly felt a strong pressure pulse preceding the emergence of a pyroclastic flow from under the clouds. The pulse followed intense rockfall activity. We interpret the pressure pulse as a vesiculation event on the dome when fresh magma became exposed at the surface after a rock avalanche.

The pyroclastic flows essentially free-fall off the very steep dome. Farther downslope, the flows decelerated rapidly and stopped at about m altitude, 2. There were 2 principal avalanche tracks down the northern flanks. Pelee in The pyroclastic flows moved in silence, unheard even from very close range m. This is in striking contrast to the loud rattle of rock avalanches high on the dome that preceded the pyroclastic flows.

Sounds of the colliding blocks within the pyroclastic flow avalanche are apparently muffled by the elutriating fine ash. The compactness of the cauliflower cloud and observed lightning flashes lend credence to Perret's hypothesis that the dense clouds may be held together electrostatically opposite charges of steam and ash.

The basal avalanche below the rolling cauliflower clouds moved in spurts. Its thickness was probably less than a few meters. Forward-springing jets composed of relatively fine sand-sized material were clearly observed by Kienle at the snout of the avalanche.

Jets or narrow sheets of this material emerged from the top surface of the moving basal avalanche and were thrown diagonally downwards ahead of the moving flow, immediately to be overrun by the following avalanche, suggesting that a retrograde rotor turbulence was operating at the flow front. Occasionally, the basal avalanche would override and entrap a pocket of cold air behind an obstacle such as large rocks. Heating and expansion of the entrapped air caused sudden boils in the moving avalanche seconds later.

Meter-sized pumice blocks were seen emerging continuously from the flanks of the flows, leaving beautiful levees on the sides of the pyroclastic flow channels. Where we observed the flows, they were eroding, leaving U-shaped channels m wide with 2-m-high pumice levees on both sides.

Some flows also left one or more central furrows. This suggests that longitudinal turbulent rolling motions occur within the pyroclastic flows. However, we could not observe this from our viewpoint to one side of the flows. We did not notice any indraft adjacent to the pyroclastic flows, nor any incandescence, even at night, probably because they were relatively small.

Individual flows left a hot inflated gray fine ash deposit about 50 cm thick where we studied it at the m level. Larger pyroclastic flows on 28 August resulted in sand-sized ashfalls to the shoreline on the N and NW flanks. A large cloud produced by two merging pyroclastic flows passed overhead at the Burr Point camp 6 km N of the summit at , showering sand-sized particles on us for about 5 minutes. The sand was not hot. Miller and Kienle visited the crater on 11 September.

A new spine, about 10 m high, occupied the small crater that had existed on top of the dome during the summer. Concentric ring fractures and alternating circles of moats and arches attest to endogenous dome growth and final extrusion of a spine above the central magma stem.

New material was also added to the N face of the dome since we had last seen it on 17 July. Temperatures of March-April pyroclastic flows. Cooling is now taking place from the bottom and top of the deposits, with a temperature reversal below 4. Further References. Rose, W. B5, p. Swanson, S. Augustine: field test of a hazard evaluation: JGR, v. Yount, M. Kienle and J. When first observed, the plume was described as dirty steam with dark streaks at to m altitude, but it rose to about 2,, m altitude within several minutes.

At , on their return from Kodiak to Anchorage, the pilots observed the plume spreading E and topping out slightly higher than m altitude. The volcano has emitted steam continuously since its eruption. Less than 4 minutes before the plume was first observed, an earthquake with an epicenter of The event occurred at and was located by the Alaska Tsunami Warning Center at a depth of km with a local magnitude of 4. The University of Alaska Geophysical Institute seismic network detected two Augustine earthquakes at about and with above-normal magnitudes about 1.

Geologists returned to Augustine in July for additional monitoring of magnetic changes, deformation, and fumarolic activity. The following is from the Alaska Volcano Observatory. Magnetic data Dan Dzurisin.

Little change had occurred since the previous measurement in June , although similar measurements on the Mt. Geologists suggested that the proximity of a relatively active magmatic system at Augustine may retard cooling of the dome, or that differing rock magnetic properties may account for apparent differences in cooling rates. Deformation Gene Iwatsubo and John Power.

The deformation network established in June was reoccupied in early July , and several additional EDM lines were added. Preliminary data showed no significant changes in the lengths of pre-existing lines, indicating that no deformation was occurring to the cone and summit dome complex. Gas measurements Robert Symonds and Robert Andres. July fieldwork indicated that fumarolic activity had decreased significantly since the previous gas measurements in August Eruptions begin 11 January and eight outbursts occur by late January.

This report covers events from May through 26 January By late January there had been eight eruptions. A National Oceanic and Atmospheric Administration NOAA message pointed out that life-threatening costly damages can occur to aircraft that fly through an eruption cloud. It added that the Federal Aviation Administration put NOAA's information to work, giving air traffic managers and controllers a heads-up to ensure airspace safety around the volcano as well as along the forecast trajectory of the ash plumes.

The geography of the Cook Inlet, where Augustine is located, is shown on figure The last major eruption of Augustine was in March Between mid-July and early August , seismicity at Augustine began to increase.

On 17 February an explosion plume was observed over the volcano. Seismicity intensified after the end of February. On 27 March explosions sent eruption clouds into the stratosphere and generated pyroclastic flows that reached the sea.

Explosive activity, ash plumes, and pyroclastic flows continued through August and September , and Augustine steamed continuously through at least July BGVN , , Current eruption. The AVO website presents observations and remarkable photos documenting eruptive stages seen thus far.

These earthquakes slowly increased from per day to per day. Data from a Global Positioning System GPS network on Augustine indicated that a slow, steady inflation of the volcano started in mid-summer , continuing until the present. This was the first such deformation detected at Augustine since measurements began just prior to the eruption.

On 29 November AVO raised the Concern Color Code from Green to Yellow after recording important long-term changes in seismicity and ground deformation consistent with renewed volcanic unrest.

Seismicity remained at elevated levels during 30 November to 12 December During December, changes in the style of earthquake activity at the volcano were recorded, and there were reports of gas emissions and steaming.

On 12 December a steam plume visible on video and satellite images extended 75 km SE figure During a 12 December flyover, AVO scientists saw profuse steaming from numerous summit fumaroles, emanating mainly from behind the lava dome. Several energetic fumaroles were also located m down the SE flank.

A gas-and-steam plume extended 75 km SE. Reports during December mentioned that residents E of the volcano smelled sulfur; and the reports noted intervals of elevated seismicity, and several small steam explosions. A gas-measurement flight on 20 December detected SO 2 for the first time at Augustine since routine airborne measurements began in the early s.

Aerial observations and analysis of photography and video of the summit area indicated some deformation within the summit crater area. A crack or fissure was noted cutting the lava dome and extending to the SE figure Heavy steam from this feature, along with patches of bare ground, indicated an increase in the summit's heat output.

The imaging confirmed the presence of a new, high-temperature fumarole or gas vent located high on Augustine's S flank. Seismicity decreased during the last week of December compared to the previous week; but steam and gas emissions continued. AVO scientists visited the volcano to install additional GPS receivers and deploy additional ash-collection devices. Observations continued to suggest that new magma was present.

The level of seismicity was still well below that observed just prior to the eruption. During the first week of January , seismicity increased slightly compared to the previous week. The volcano continued to steam vigorously from several summit fumaroles.

AVO scientists visited the volcano to install additional seismic monitoring equipment, to deploy additional ash-collection devices, and to undertake helicopter-aided thermal surveys of the summit area. The high-temperature fumarole or gas vent on Augustine's upper S flank, previously reported on for 22 December, had cooled significantly, but elevated temperatures were detected at one summit fumarole imaged through the steam and gas.

Although fumarole temperatures varied, there were no significant changes in the distribution of thermal features compared to the previous survey. A gas-measurement flight detected a significant increase in SO 2 compared to 20 December. Earthquake activity beneath Augustine had increased markedly, indicating the heightened possibility of an explosive eruption within hours to days.

Satellite data confirmed that an ash cloud was produced and, in collaboration with the National Weather Service NWS , the top of the cloud was estimated at 9 km altitude.

By , the ash cloud had traveled 40 km E and 50 km N. An ash-fall advisory was issued by the NWS at Seismicity decreased significantly after the explosions.

During an 11 January afternoon overflight, AVO scientists observed a pure white steam cloud rising to about 3. Little volcanic ash was observed on the island itself, but volcanic mudflows were evident on the E, S, and W sides of the volcano figure A brown haze in the air was observed over the central part of Cook Inlet.

After the eruption on 11 January, seismic activity declined. Explosive eruptions on 13 and 14 January produced clouds of volcanic ash and flows of mud and rock fragments.

A marked increase in seismicity early on 13 January preceded an eruption interval that began at around and ended around NWS subsequently reported ash heights of 10 km altitude. Other explosive events followed on 13 January, occurring at , , figure 21 and ; and on 14 January at figure Each of these events produced ash plumes, mudflows, and pyroclastic flows on the island.

Ash clouds surpassed 9 km altitude, as reported by pilots and determined by radar data provided by the National Weather Service NWS. Ash was carried to the E-SE and light ash falls were reported in communities of the southwestern Kenai Peninsula. According to preliminary assessment by Pavel Izbekov Geophysical Institute, University of Alaska Fairbanks and AVO , the majority of ash particles in the 13 January seemed to be juvenile, though there are large variations in the morphology of ash particles as well as the composition of matrix glass.

Enlargements of two ash grains appear in figures 23 and These diffuse ash-and-gas clouds were presumably from Augustine's explosive events on 13 January. Seismicity declined in the 30 hours after the event early on 14 January, and AVO downgraded the color code from Red to Orange.

The level of seismic activity at the volcano remained above background. On 17 January an explosive eruption began at and ended at Seismic and pressure-sensor data indicated numerous small explosions, which could produce small amounts of low-level ash and could initiate small rock avalanches on the flanks.

AVO raised the concern color from Orange to Red. A flight later on 17 January disclosed a brown ashy haze lingering over the island. Occasional views through the haze showed that most of the lava dome that formed following the 14 January eruption was destroyed in the explosion of 17 January. Observations made during a flight on the afternoon of 18 January indicated that the summit was steaming vigorously, consistent with the formation of a new lava dome. Evidence of explosive ejection of volcanic bombs included circular craters the size of large trucks seen on the NW flank.

Block-and-ash-flow deposits with car-sized blocks produced by dome collapse covered parts of the SE flank. Surge deposits were observed on the NW flank. A white steam plume was observed rising to about 2, m altitude before it trailed off as a bluish haze to the E. Little to no ash appeared to be present in the plume. After the eruption at on 17 January, seismicity diminished significantly and AVO lowered the color code from Red to Orange late on 18 January.

By the morning of 19 January seismicity remained fixed at lower levels; it decreased further on 20 January but still stood above background. Periods of quiescence and low seismicity in the intervals between eruptive events are not unusual at Augustine, having occurred during the and eruptive episodes. By 25 January seismic activity at Augustine remained low but above background levels. During January, satellite observations indicated the persistence of faint thermal anomalies.

On 26 January steaming continued at the summit figure January eruptions; pyroclastic flows, ash plumes, and aviation hazards. Following a period of increased seismicity at Augustine that began in May , discrete seismic events on 9 and 11 December may have perturbed the hydrothermal system, initiating small steam explosions.

On 12 December, a plume extended 75 km SE of the volcano, and its S and E flanks were dusted with ash likely non-juvenile. Additional steam explosions took place later in the month, and the smell of sulfur was reported by residents in villages on the E side of Cook Inlet. The first major eruptions at Augustine occurred on 11 January , when two discrete explosions produced an ash cloud that reached 9 km altitude BGVN and the Concern Color Code was raised to Red.

Further eruptions occurred on 13, 14, and 17 January. By the morning of 19 January seismicity remained fixed at lower levels; it decreased further on 20 January but was still above background.

During January, satellite observations indicated the persistence of faint thermal anomalies and steaming continued at the summit. Occasional intervals of increased seismicity were observed for the next few days. On 27 January an explosive eruption began at about and lasted for 9 minutes.

AVO raised the color code from Orange to Red. Augustine erupted again at on 27 January This event lasted 1 minute and no ash was detected above 3 km. A third eruption occurred at on 28 January and lasted 2 minutes.

A fourth eruption occurred at on 28 January and lasted 3 minutes; the ash cloud drifted SE at a maximum altitude of 7. Another explosive event began at on 28 January. Seismic activity continued and continuous ash emission was observed in AVO web camera images. Webley, Kenneson G. Dean, Jonathan Dehn, John E. Wessels, Michelle L. Coombs, David J. Schneider, Jonathan Dehn, and Michael S.

Ramsey page PDF; West, Stephen Blake and David A. Rothery page PDF; 4. Sentman, Stephen R. McNutt, Hans C. Thomas, Stephen R. McNutt, Paul R. McGee, Michael P. Doukas, Robert G. McGimsey, Christina A. Neal, and Rick L. Adleman, Cheryl E. Cameron, Seth F. Snedigar, Christina A. Neal, and Kristi L. Wallace page PDF; 2. Neal, Thomas L. Murray, John A. Power, Jennifer N. Adleman, Paul M. Whitmore, and Jeffery M. Osiensky page PDF; kB.

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Download the latest version of Adobe Reader, free of charge. Power, J. Geological Survey Professional Paper , p.

Buurman, Helena and West, M. Jacobs, K. McNutt, S. DeShon, H. Fisher, M. Lalla, D. Coombs, M. Wallace, K. Vallance, J. Waitt, R. Reid, M.

Larsen, J. Augustine Island has a land area of The irregular coastline of Augustine Island is due to the repeated catastrophic collapse of the summit dome, forming debris avalanches down the flanks and into Cook Inlet.

Jurassic and Cretaceous sedimentary strata form a bench on the south side of the island and are overlain by granitoid glacial erratics and volcanic hyaloclastites. The volcano consists of a central dome and lava flow complex, surrounded by pyroclastic debris.

Access to the Atlantic Ocean is via the St. Augustine Inlet of the Matanzas River. Augustine has a humid subtropical climate or Cfa — typical of the Gulf and South Atlantic states.