Volcanic activity at Soufrière Hills remained at a high level, similar to the previous week. Lava dome growth on the western side of the dome complex produced rockfalls to the W that were confined by the collapse scar formed on 29 July 2001. The dome complex consists of the stagnant E lobe (870 m a.s.l.), an inactive central lobe (930 m a.s.l.), and the active W lobe (960 m a.s.l. on 27 November).
During 23-30 November a lava dome continued to grow in Shiveluch's active crater, and small eruptions produced gas-and-steam clouds. The highest reported gas-and-steam cloud rose to 1.3 km above the dome on 27 November. Thermal anomalies in the active dome area were visible on satellite imagery.
Seismicity returned to normal levels on 25 November after a moderate-to-large volcanic earthquake occurred at Ruapehu on 21 November. Observations on 25 November revealed no signs of eruptive activity. Scientists found that upwelling sediment in Ruapehu's crater lake caused the lake to change from its normal blue-green color to dark gray.
During the week, Popocatépetl emitted small clouds of steam, gas, and minor amounts of ash. In addition, episodes of harmonic tremor were recorded.
During 19 November- 2 December VSI personnel observed 90 incandescent lava avalanches traveling SW, predominately to the upstream portion of the Sat River, and to a lesser extent to the Lamat and Senowo rivers. The maximum run-out distance was 2.5 km. During the report period, seismicity was dominated by avalanche earthquakes that were similar in frequency and magnitude to those of the previous week.
Volcanic activity at Kilauea remained similar to the previous week, with lava flowing into the ocean at the Kamoamoa and E Kupapa`u ocean entries and surface lava flows at spots along the Kamoamoa lava tube system. Generally, seismicity was normal at the volcano; volcanic tremor was at low-to-moderate levels at Pu`u `O`o and low at Kilauea's summit. Tiltmeters along the volcano showed no significant deformation.
During 26 November- 2 December seismicity was dominated by 664 small explosion earthquakes. White, thick plumes rose 50-300 m above the volcano, which remained at Alert Level 2 (on a scale of 1-4).
Since 27 November weak, continuous spasmodic tremor was recorded at Karymsky. The volcano remained at Concern Color Code Yellow.
Wed, 28 Nov 2001, 06:00
Tremor was recorded at Guagua Pichincha for ~16 hours after a phreatic eruption on 26 November. Signals from a relatively high number of rockfalls were recorded on seismographs, which is normal after an explosion. Two new craters formed during the explosion N of the 1981 crater.
Read allWed, 21 Nov 2001, 06:00
The level of volcanic activity at Soufrière Hills increased during 16-23 November in comparison to the previous week. Morphological changes were observed at the volcano's summit; lava-dome growth shifted from the E to the W and the summit area was crowned by spines with an average elevation of 940 m a.s.l. Rockfall activity was relatively low, but intensified towards the end of the report week.
Read allWed, 21 Nov 2001, 06:00
IG's seismic data showed that an approximately 20-minute-long phreatic explosion began at Guagua Pichincha on 26 November around noon. Cloudy conditions prohibited visual observations, but a cloud composed mainly of gas, with small amounts of ash, may have been produced. The volcanic cloud was not visible in satellite imagery; it is believed to have stayed around summit level.
Read allWed, 21 Nov 2001, 06:00
During 16-23 November a lava dome continued to grow in Shiveluch's active crater, and several eruptions produced ash, steam, and gas clouds. The highest reported ash cloud rose to 1-2 km above the dome on 19 November. Thermal anomalies in the active dome area were visible on satellite imagery.
Read allWed, 21 Nov 2001, 06:00
On 21 November at 0218 a moderate-to-large volcanic earthquake was recorded at Ruapehu. The earthquake was followed by ~1 hour of moderate-to-strong volcanic tremor. IGNS did not believe an eruption accompanied the earthquake because no air waves were recorded and there were no reports of unusual activity.
Read allWed, 21 Nov 2001, 06:00
During the week, Popocatépetl emitted small clouds of steam, gas, and minor amounts of ash. In addition, episodes of harmonic tremor were recorded. During a flight over the volcano on 21 November observers noticed a new 130-m-diameter lava dome growing inside the internal crater.
Read allWed, 21 Nov 2001, 06:00
News reports on 21 November stated that lahars were generated at Mayon after several days of heavy rainfall mixed with unconsolidated material on the volcano's slopes. According to the civil defense, flooding caused more than 4,800 families to be evacuated from their homes.
Read allWed, 21 Nov 2001, 06:00
A gradual decrease in seismicity under Kliuchevskoi during 16-23 November led KVERT to reduce the Concern Color Code from Yellow to Green. The tallest gas-and-steam plume of the reporting interval was produced on 19 November. The plume rose 700 m above the dome and extended SE for more than 10 km.
Read allWed, 21 Nov 2001, 06:00
Lava continued to flow into the ocean at the Kamoamoa and E Kupapa`u entries. HVO personnel confirmed that the Kupapa`u entry was inactive, as was reported the previous week. Surface lava flows were visible near the E Kupapa`u entry and at spots above, on, and below the Pulama pali scarp along the Kamoamoa lava tube system.
Read allWed, 21 Nov 2001, 06:00
A visit to Kavachi on 25 November revealed sulfur, mud, and tiny pieces of volcanic rock upwelling from the submarine volcano. The pieces of volcanic rock covered the sea surface over an area more than 100 m across. No explosive eruptions were seen during a 6 hour observation period.
Read allWed, 21 Nov 2001, 06:00
A noticeable decrease in seismicity at Karymsky during the end of the week of 16-23 November led KVERT to reduce the Concern Color Code from Orange to Yellow. Seismicity remained slightly above background levels after the decrease in earthquakes and signals of possible ash-and-gas explosions. On 19 November an airline pilot reported that the volcano's edifice looked black.
Read allWed, 21 Nov 2001, 06:00
As of 23 November, frequent Strombolian eruptions (~1-10 per day) occurred from a persistent ~15-m-diameter summit lava lake at Erebus. In addition, infrequent small ash eruptions took place at a vent adjacent to the lava lake.
Read allWed, 14 Nov 2001, 06:00
Several steam, gas, and ash emissions occurred at Tungurahua during the week. On 18 and 19 November emissions with significant amounts of ash were observed rising to 2 km above the volcano as they drifted to the W and NW. IG warned that mud flows could be generated by ash on the flanks mixing with rain during periods of heavy rainfall.
Read allWed, 14 Nov 2001, 06:00
An increase in seismicity at Kliuchevskoi during 13 November to at least 16 November led KVERT to raise the Concern Color Code from Green to Yellow. On 13 November at 1619 seismicity sharply increased from background levels when a swarm of shallow earthquakes began; these had magnitudes less than or equal to 3. During 13-15 November more than 150 earthquakes occurred with magnitudes less than or equal to 1.7.
Read allWed, 14 Nov 2001, 06:00
Increased seismicity at Karymsky during 11-16 November led KVERT to raise the Color Concern Code from Yellow to Orange. Beginning on 11 November seismicity was above background levels and many earthquakes and episodes of high-frequency spasmodic volcanic tremor were registered beneath the volcano. On 15 November at 0830 seismicity increased and earthquakes and signals of possible weak ash-and-gas explosions were registered.
Read allWed, 14 Nov 2001, 06:00
Volcanic activity at Soufrière Hills during 9-16 November was generally diminished compared to the previous week. The lava dome continued to grow mainly towards the E and its highest point was measured on 9 November to reach 876 m a.s.l. Small pyroclastic flows and rockfalls were generated by material avalanching off the flanks of the dome.
Read allWed, 14 Nov 2001, 06:00
During 9-16 November a lava dome continued to grow in Shiveluch's active crater and several steam, gas, and ash explosions occurred. Seismic data suggested emissions from these explosions rose to a maximum height of ~4 km above the dome. A short-lived explosion on 9 November at 1200 produced an ash plume that was observed from Klyuchi, ~46 km from the volcano, rising ~1 km above the dome.
Read allWed, 14 Nov 2001, 06:00
During the week, Popocatépetl emitted small clouds of steam, gas, and minor amounts of ash. There were episodes of increased emissions and seismometers recorded periods of harmonic tremor. According to CENAPRED, this type of activity may be associated with lava dome growth, as occurred on 15 August and 10 September 2001.
Read allWed, 14 Nov 2001, 06:00
During 5-18 November VSI personnel observed 192 incandescent lava avalanches traveling SW, predominately to the upstream portion of the Sat River, and to a lesser extent to the Lamat and Senowo rivers. The maximum run-out distance was 3 km. During the report period, seismicity was dominated by avalanche earthquakes.
Read allWed, 14 Nov 2001, 06:00
Following a tectonic earthquake near Lokon on 19 October, activity increased at the volcano; high-frequency tremor occurred and gray emissions rose 50-250 m above Tompaluan crater. While fewer earthquakes were recorded during 12-18 November (10 per day) in comparison to the previous week (19 per day), the number of earthquakes was still above normal levels. No major changes in volcanic activity were seen at Lokon's summit.
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