Precursory data used as a basis for the forecast included seismicity figure 36 , sulfur-dioxide fluxes BGVN , and tilt e.
In accord with JMA's precursory warnings, representatives of Komoro City decided to close the mountain hut 2 km W of the summit. The afternoon of 1 February, the resident and official observer there, Keisuke Kanda, readied the hut for closure.
After that, he went to bed, planning to climb down the mountain the next morning. At the time of the eruption he neither felt nor heard any disturbance.
At about 9 minutes after the eruption began , he was awakened by his ringing cell phone. Volcanic bombs were thrown to the N as far as 1 km. For comparison, the eruption of 1 September had a recorded air wave of Pa. Cities recording ashfall included Karuizawa, Kamogawa, Tomioka, Chichibu, and in the broader Tokyo metropolitan area, Kawasaki, and Yokohama. Aviation sources suggested that the 2 February eruption only lasted until that is equivalent to 1 February during UTC.
Charles Holliday noted airport weather data. The video said that Yokota received mm of ashfall but the features in the field of view appeared to show considerably less, perhaps suggesting some areas of thickened ash deposition. Holliday noted that ash fell at the Base hours after the eruption; although he was unable to establish the exact start time there, ashfall ended at During the eruption, Masakatsu Umeda, working in a French restaurant 7 km N of the summit, felt small but continuous shaking and saw a red plume rising from the summit crater.
He heard a far softer sound than he did on 1 September but then he was 4 km NE of the summit at Rokurigahara parking lot. An 18 February JMA report presented a sequence of night photos capturing incandescent explosions on 2 February at and for the next 15 minutes figure These photos portray the eruptive stage often termed the jet- or gas-thrust phase see diagrams and models on a website by Camp, Waning eruptions during next few months.
A series of small eruptions followed, including those on 9, 10, 11, 16, and 17 February, 15 and 23 March, and at least as late as 2 May. The hazard status, initially raised to 3 on 1 February, dropped to 2 on 7 April. JMA said that on 9 February at , a plume rose m above the summit; at , a plume was 1, m above the summit. A trace of ashfall blew NE, to Kitakaruizawa. As of on 10 February, the plume height was m above the summit; at , it was m. As of on 10 February the plume height was m above the summit.
Takayuki Nagai, a teacher at a middle school 12 km N of Asama's summit; said that few students arriving there appeared to recognize that the eruption continued. One had seen a gray ash plume. As of on 11 February, the eruption apparently continued, but JMA could not see plumes, probably because of bad weather. The eruption determination was seemingly based on elevated seismicity. JMA noted an eruption during on 16 February.
A colored plume rose to m above the summit and moved E. Asama again erupted at on 17 February. A plume bearing ash rose to m above the summit, and moved to E.
Web cameras disclosed crater glow. JMA reported incandescence from the crater on 23 March, and an observer 50 km E at Maebashi saw strong steam plumes on 30 March. Although authorities had lowered the alert level, similar eruptions continued with plumes to 3. This was the last eruption clearly noted in available reports through the end of May.
Several detailed maps of the SE-trending, elongate cigar-shaped deposits were compiled in the days after the eruptions. Such detailed maps figure 41 enabled scientists to estimate the mass of material that fell on Honshu Island.
For the map in the proximal region inset , traverses were made across portions of the tephra deposits in early February at approximate distances of 5, 10, and 13 km from the crater. Besides showing points with measurable ash solid circles , the maps disclose considerable points where the ash was absent or negligible open circles.
Such deposits are often ephemeral, owing to post-depositional processes such as wind and particularly rainfall, which frequently strip the tephra away before detailed measurements. Additional fine ash clearly blew beyond the coastline, settling over the adjacent Pacific Ocean. Figure 42 illustrates the near-source deposit's mass assessment for figure 41 inset.
This yielded an erupted-mass estimate of about 2. Various other maps and solutions for contours exist. Figure 43 presents basic grain-size information on the deposit. The photo shows some of the larger grains found at distance from the vent.
The grains consisted largely of pre-existing rocks. These juvenile grains were rhyolitic to dacitic.
Few thin ash blankets have been assessed in more detail than the one shown here. The relevance of these efforts include understanding the character and size of the eruption and calibrating ashfall with satellite observations. Volcanic Ash Advisory Centers VAACs regularly model eruptions such as this in order to forecast the transport of ash in the atmosphere.
This is based in part on the height of ash plumes and on meteorological observations such as wind-velocity profiles. One goal of those ash transport models is to steer aircraft clear of ash in the atmosphere. Volcanic ash plumes can reach higher altitudes than commercial aircraft can fly, and encounters with ash may lead to severe engine damage.
Camp, V. Minakami, T. Fundamental research for predicting volcanic eruptions part 1 ; Earthquakes and crustal deformations originating from volcanic activities: Bull. Earthquake Res. McNutt, S. Colored eruption plumes cease after 27 May ; steaming and seismicity through Periods of increased seismicity were detected throughout the year. JMA monthly reports, available through December , noted observations of white plumes in May , with a grayish-white plume rising to m above the Kamayama Crater on 27 May.
White plumes in June remained below m height. In July, white plumes rising no higher than m were seen on nine days. Similar plumes were seen during August on 19 days and continued to be observed almost daily through the remainder of Seismicity increased again after 25 October, rising to events on the 30th, and a monthly total of 1, Overall December seismicity was back to the level recorded earlier in the year with 2, events, with an increase after the 25th, and a high of earthquakes on the 29th.
No changes in high-temperature areas around summit crater; seismicity remained low. Only two minor incidents were noteable during the end of the year. During November seismic activity was at a low level, though it was slightly above background. No remarkable changes were noted by either GPS or tiltmeter observations. Alert Level 1 continued during this period. High-temperature areas were confirmed in and around the center of the summit crater. No changes in the distribution of thermal anomalies was detected since the last observation on 13 April.
In December, seismic activity continued at a low level except for a slight increase during December. These reports have been translated into English since October and can be viewed online see Information Contacts section below. Based on JMA monthly reports, there was no exceptional activity during However, during , the frequency of shallow volcanic earthquakes and tremors occurring immediately under the summit crater began to increase.
In late April , volcanic seismicity further increased. Because of this increase in activity and the possibility of a small eruption, JMA raised the Alert Level on 11 June from 1 to 2 on a scale of 5 , and warned people not to approach the crater. The volcano remained in "a somewhat active state" in through at least September, and JMA kept the Alert Level at 2 through that time. Very small eruptions were reported by JMA from the summit crater on 16 and 19 June that generated ashfall to the NE within 4 km of the crater.
Scientists aboard an overflight later that day observed the crater venting white to blue-white gas. No further eruptions occurred through the end of December JMA reported that the number of very weak volcanic earthquakes and tremors at a very shallow depth immediately under the summit crater had shown a long-term increasing trend since around The number began to increase further during late April and, although decreasing slightly since August, remained high through at least December.
On 14 October , government scientists observed a thermal area around the bottom of the summit crater during an aerial inspection; this finding was similar to the previous observation on 24 June No new ejecta or discoloration were seen in or around the crater, and no changes in the crater morphology were observed.
According to JMA, white plumes rose as high as m above the crater rim in November and m above the rim in December. They also reported that between July and December , weak night-time incandescence at the summit crater was visible. The level remained high through at least the end of the year table 3.
Table 3. A slight extension was observed along some baselines from about May to September Contraction was also observed between the summit and Oiwake 8 km SSE during June-September, based on electro-optical distance measurements. JMA interpreted this as possible inflation at shallow depths under the summit.
Both methods indicated that contraction had ceased by October Tiltmeter data indicated that deeper parts under the western side of the summit had inflated slightly during early June; this trend slowed in late July and remained slow, but ongoing, through December This compilation of synonyms and subsidiary features may not be comprehensive.
Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.
The modern Maekake cone forms the summit and is situated east of the horseshoe-shaped remnant of an older andesitic volcano, Kurofuyama, which was destroyed by a late-Pleistocene landslide about 20, years before present BP.
Growth of a dacitic shield volcano was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,, BP, and by growth of the Ko-Asama-yama lava dome on the east flank. Maekake, capped by the Kamayama pyroclastic cone that forms the present summit, is probably only a few thousand years old and has an historical record dating back at least to the 11th century CE. Maekake has had several major plinian eruptions, the last two of which occurred in Asamayama's largest Holocene eruption and CE.
The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Aramaki S, Geological map of Asama volcano. Geol Surv Japan , , geol map and text in Japanese with English summary. Asama volcano. Asama and Fuji volcanoes. Green J, Short N M, New York: Springer-Verlag, p. Hayakawa Y, Nakajima H, Volcanic eruptions and hazards of Asama written in historical records.
Asama and Haruna volcanoes: recent eruptions and hazards. Climatic impact of explosive volc conf, Tokyo, Dec , , 28 p guidebook.
Japan Meteorological Agency, National Catalogue of the Active Volcanoes in Japan second edition. Tokyo: Japan Meteorological Agency, p in Japanese. Japan Meteorological Agency. Volcanic tremor associated with the Asama volcano eruption on February 6, Kudo T, Hoshizumi H, Catalog of eruptive events within the last 10, years in Japan, database of Japanese active volcanoes.
Kuno H, Japan, Taiwan and Marianas. Quaternary Volcanoes of Japan. Suzuki T, Discharge rates of fallout tephra and frequency of plinian eruptions during the last , years in the southern Northeast Japan arc. Quat Internatl , Yasui M, Koyaguchi T, Sequence and eruptive style of the eruption of Asama volcano, central Japan: a case study of an andesitic explosive eruption generating fountain-fed lava flow, pumice fall, scoria flow and forming a cone.
Bull Volcanol , The eruption of Asama volcano, Central Japan. Bull Volc Soc Japan , Murase, M. Time dependent model for volume changes in pressure sources at Asama volcano, central Japan due to vertical deformations detected by precise leveling during Remarks: A large inflation can be modeled by a volume change of 6e7 cubic meters at a depth of 6 km beneath Kurofu volcano.
The maps shown below have been scanned from the GVP map archives and include the volcano on this page. Clicking on the small images will load the full dpi map. Very small-scale maps such as world maps are not included. The maps database originated over 30 years ago, but was only recently updated and connected to our main database. We welcome users to tell us if they see incorrect information or other problems with the maps; please use the Contact GVP link at the bottom of the page to send us email.
Catalog number links will open a window with more information. Figure A surveillance camera observed faint incandescence at Asamayama in February Left: Onimushi surveillance camera taken at on 5 February Right: Kurokayama surveillance camera taken at on 1 February Surveillance camera images of Asamayama showing the small eruption at the summit crater on 7 August , resulting in incandescence and a plume rising 1.
Both photos were taken on 7 August Source: Japan Meteorological Agency JMA 3 February-9 February Cite this Report On 5 February JMA lowered the Alert Level for Asamayama to 1 on a scale of noting that no deformation or crater incandescence had been detected since late November , sulfur dioxide emissions had trended downward beginning in December, volcanic earthquakes were recorded only occasionally since mid-December, and the number of small-amplitude volcanic tremors were recorded occasionally and had not increased.
Source: Japan Meteorological Agency JMA 14 August August Cite this Report JMA reported that, after a small phreatic eruption occurred at Asamayama on 7 August, both seismic activity and sulfur dioxide emissions temporarily increased and then decreased later that day. Information is preliminary and subject to change. All times are local unless otherwise noted February CSLP First explosive activity in 11 years causes ashfall in early February Card 07 February Explosion on 1 February the first since "On 1 February, GMT 26 sec the Asama volcano blew up with a terrific explosion after 11 years of silence, since the activity on 7 November Preliminary distribution of ashfall from the explosion of Asama on 1 February Figure 2.
Number of seismic events recorded per month at Asama, January November The eruptions of February and March are indicated by arrows at the top. Figure 3. Daily number of earthquakes recorded at Asama, August Figure 4.
Top: Maximum monthly height in kilometers of the volcanic plume from Asama, January March Bottom: Monthly number of recorded seismic events at Asama, January March Figure 5. Area of ashfall shaded region from the eruption of Asama, 26 April. Figure 6. Daily number of recorded seismic events at Asama, March-May The 26 April eruption is marked by an arrow. Figure 7. Daily number of recorded volcanic tremor events top and B-type earthquakes bottom at Asama, January-April Figure 8.
Area of ashfall from Asama, 8 April Figure 9. Daily number of recorded earthquakes at Asama, June top , with detail showing daily recorded earthquakes during January June bottom. Arrows mark eruptions. Height of steam emission from Asama, January-June Monthly mean cloud height at Asama, Arrows at top mark eruptions. Monthly number of earthquakes at Asama Daily number of recorded earthquakes top and tremor episodes bottom at Asama, January early May Arrow marks small ash eruptions on 20 July Daily number of earthquakes at Asama, 1 January 31 May Plot showing volcanic earthquakes registered at Asama during June The number of earthquakes peaked on 22 June around and gradually decreased, reaching background levels on 24 June.
Courtesy of Yukio Hayakawa, Gunma University. A fresh impact crater formed by a large bomb from the 1 September Asama eruption. The center photo also shows two big craters in the center right; a trail following the outer crater rim is largely tephra covered but segments remain recognizable.
Courtesy of the Geological Survey of Japan captions and photos by H. Hoshizumi, GSJ. The base map is in Japanese but English names have been added to selected urban areas. The three orthogonal components are shown as follows: Upper row is in the E-W direction, middle row is in the N-S direction, and bottom row is in the up-down direction. Courtesy of Simon Carn and L. Topographic map showing the flight lines and locations of aerial photos at Asama volcano N is towards the top , 3 September Courtesy of Asia Air Survey Co.
Aerial photo of Asama taken on 3 September ; the shot was taken at the point labeled "90" on line C3 on figure 22, in effect, from a point slightly E of the summit crater.
Copyrighted photo is used here with permission of Asia Air Survey Co. Taken at on 14 September. Courtesy of A. Tomiya, GSJ. The real communication patterns are considerably more complex and involve other communication links, such as those of the air carrier, between its aircraft to its own offices, and those directly between local observatories and meteorological offices.
Inputs from people monitoring a volcano pass through a system with different conventions and procedures. Advisories such as this are the messages received on the flight deck of potentially affected aircraft and by the air carriers' dispatchers. N is up. Radiated microwaves were transmitted from the N, at 4, m altitude, 2 km from the crater, with the off-nadir angle of 55 degrees. Courtesy of the Geographical Survey Institute.
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Batu Tara photos A remote island in the Flores Sea of Indonesia formed by a single volcano that has been in strong strombolian eruption for years. We regularly lead expeditions to there where we camp several days to observe it. Photo Tours. These tours are ideal if you are interested in learning or improving photography or, if you are an experienced photographer yourself, to get to the best locations at the best times.
Get the ad-free version! Why is there advertising on this site? Support us - Help us upgrade our services! Asama has had several major plinian eruptions, the last two of which occurred in and AD.
Asama is heavily monitored with seismographs and videos cameras. Ashfall was reported in Tokyo, km SE of the volcano. This was the first activity at the volcano since Incandescent blocks were ejected several kilometers from the summit and caused many fires.. HOME Back. Saimyoji Temple. Naena Falls.
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