Small phreatic eruption from the Kudriavy summit forms a new crater

Changes in activity at the Kudriavy cone (figure 2) were detected in mid-September 1999, preceding an eruption on 7 October. Since 1989 the temperatures of sediments in the dry lakes within the crater (lakes temporarily exist after snow melting and strong rains) at a depth of 0.75 m have consistently fallen in the range of 48-82°C, with fluctuations of 3-5°C. In contrast, September 1999 measurements at the control points in the Hot Lake area showed increasing temperatures of 60-102°C. [These temperature measurements have been made 1-3 times each year.]

Figure 2. Photograph of fumarolic plumes rising from the crater of the Kudriavy cone at Medvezhia, September-October 1999. Courtesy of G.S. Steinberg.

The weather in August, September, and October was unusually dry for the region, with rain only during 24-25 September and 2-3 October. A temperature survey of two lakes was made in September. Usually, lakes exist 1-2 days after rains, but the water in Hot Lake still covered more than half the area on 4 October. Temperatures in the dry part of the lake had increased by 14-22°C. The lake water close to the hot dome was boiling and seething due to gas emissions. [The hot dome is 150-170 m in diameter, rising 60-70 m above the bottom of Hot Lake to the W and 30-40 m above the bottom of the dry lake to the S.] On 5 October the diameter of the lake was 15 m. That day two channels were excavated to allow the water to drain so that sediment temperatures could be measured. The temperature increase in this newly drained area was more than 30°C. Fumarole gas compositions during the second part of September showed increased hydrogen, oxygen, and fluorine. Sulfur ignition was seen in some locations. The number of earthquakes also increased, and although the one-channel seismic station deployed was insufficient to determine any hypocenters, the elevated seismicity was obvious. District and province authorities were warned three days before the start of the 7 October eruption that Kudriavy was unstable and could erupt soon. [On the evening of 4 October the Governor of Sakhalin and the Mayor of Kurilsk were notified that activity at Kudriavy had rapidly increased and that an eruption was expected to begin during the week of 8-15 October, with possible stronger activity later in the month.]

From the base camp, 3.5 km W from the volcano, black and gray clouds of gas and ash were observed rising above the usual fumarolic plumes at 1735 on 7 October and then extending ~10 km NW. Ejections of gas and ash occurred at intervals of 1-2 minutes. Because of the strong winds, maximum altitude of ejections was 1,100 m. The upper camp was at 940 m elevation, 30-40 m from the crater edge and 300 m from Hot Lake (figure 3). Because of strong winds, bad visibility, and the low-intensity start of the eruption, volcanic tremor and gas-and-ash ejections were not noticed in the upper camp until 10 minutes after observers in the base camp saw the plume. Night observations showed that intense ejections stopped at 0200 on 8 October. Observations through the clouds of the N part of the crater revealed "slight reddish lights - reflected light of the hot rocks and blue lights - light of the burning sulfur" that marked the edges of a crater.

Figure 3. Aerial photograph of the N part of the Kudriavy crater at Medvezhia showing the locations of the upper camp and the new explosion crater W of the hot lava dome during 7-8 October 1999. North is to the left. Courtesy of G.S. Steinberg.

No juvenile ash was identified, so the eruption was determined to be phreatic. This eruption was similar to a geyser eruption: periodic vertical ejection of the gas, ash, and steam. Ejecta didn't fall more than 30-40 m from the new crater. The surface of Hot Lake was covered by rocks with diameters of 20-30 cm, and ashfall deposits were concentrated to the NW. The volume of erupted material was nearly 40,000-45,000 m³. Areas with rhenium mineralization (see BGVN 20:10) located on the dome were not involved in the eruption or covered by eruption products. The first phase of the eruption was over on 13 October.

The eruption created a new crater in the Hot Lake area and removed part of the dome (figure 4). The crater was elliptical with dimensions of 30 x 40 m and a depth 35-40 m from the bottom of the lake and 80-110 m from the flat part of the dome (figure 5). The walls of the crater were vertical. In the lower part of the S crater wall was a 6 x 8 m cave of incandescent rocks. Based on the light intensity, the temperature was estimated to be higher than 1,000-1,100°C. Hot gas rose from this area and condensed 40-60 m above the edge of the crater. Small fiery areas and fragments with burning sulfur were seen on the S, W, and N walls. [Minor explosions continued from the cave until 13 October. Activity then declined, consisting of gas emissions with some small rock fragments that didn't reach the crater rim. No significant changes were noted through 2 November, when observations ended.]

Figure 4. Photograph of the hot dome and dry lake area in the N part of the Kudriavy crater at Medvezhia prior to the 7-8 October 1999 eruption. Courtesy of G.S. Steinberg.

Figure 5. Photograph of the 7-8 October 1999 crater adjacent to the hot dome in the N part of the Kudriavy crater at Medvezhia, October 1999. Courtesy of G.S. Steinberg.

Information Contacts: Genrikh S. Steinberg, Institute of Volcanology and Geodynamics, Russian Academy of Natural Science, Box 18, Yuzhno-Sakhalinsk 693008, Russia.

Information is preliminary and subject to change. All times are local (unless otherwise noted)

December 1981 (SEAN 06:12) Cite this Report

Intense fumarolic activity from the Kudriavy cone

The 20 September 1981 aerial inspection [of the volcanoes in the S and central Kuril Islands] revealed intense fumarolic activity at five sites in Kudriavy crater.

Information Contacts: G. Steinberg, Sakhalin Complex Institute.

April 1987 (SEAN 12:04) Cite this Report

Intense fumarolic activity

Intense activity from a few groups of fumaroles in Kudriavy's summit crater was occurring during a 6 November aerial survey. Sulfur deposits were noted around the fumaroles. East of the crater, on the outer dome slope, very intense gas emission (more active than in the crater) was observed.

Information Contacts: G. Steinberg and B. Piskunov, Yuzhno-Sakhalinsk.

March 1989 (SEAN 14:03) Cite this Report

Gas emissions from Kudriavy cone rise 300-400 m

During a 14 January overflight, strong gas emission from Kudriavy's crater formed a cloud that reached 300-400 m above the summit. The inner part of the crater was not visible.

Information Contacts: G. Steinberg, Yuzhno-Sakhalinsk.

December 1992 (BGVN 17:12) Cite this Report

Intense fumarolic activity

Fumarolic activity was intense during fieldwork in late 1992. The maximum fumarole temperature measured August-October 1992 was 910°C (figure 1), and rocks at 20-30 cm depth glowed red. CO₂-rich gases were sampled in August 1990 (table 1).

Figure 1. Sketch map of the summit area of the Kudriavy cone at Medvezhia, showing fumarole temperatures and elevations of some thermal features, August-October 1992. Contour interval is 10 m. Triangles mark collection sites for gas samples. The inset map shows Iturup Island, with locations of Kudriavy, Baransky, and Ivan Grozny volcanoes, plus the NE corner of neighboring Kunashir Island. Courtesy of G. Steinberg.

Table 1. Fumarole temperatures, mole percent H₂O, and volume percent of dry gas species from Kudriavy, August 1990. Data does not include N₂, O₂, or Ar. Sample localities are shown on figure 1. Analyses by U.A. Taran and U.A. Ignatorich. Data courtesy of G. Steinberg.

Information Contacts: G. Steinberg, Yuzhno-Sakhalinsk.

August 1995 (BGVN 20:10) Cite this Report

Measurements of SO₂ in Kudriavy plume

The Kudriavy cone at Medvezhia has been the subject of great interest since Korzhinsky and others (1994) discovered a pure rhenium sulfide mineral in its high-temperature (535°C) fumaroles. Given the concentration of Re found in gas samples (2-10 ppb), the occurrence of ReS₂ or Re₂S₃ (exact form still uncertain) requires enrichment of Re by eight orders of magnitude. During a 21 August-5 September visit, Stan Williams, Tobias Fisher, and Russian colleagues made COSPEC measurements of SO₂ flux. Gas samples were also collected from crater fumaroles.

The COSPEC was operated from the base camp (150 m elevation) 2.7 km SE of the elongate ENE-WSW summit (990 m elevation), while the wind velocity was measured at the summit using a hand-held anemometer. The first measurements were made on 28 August in vertically oriented stationary mode with the wind blowing the wide gas plume directly over the camp. Wind velocity was measured at 3 m/s and the plume was estimated to be rising only 50 m above the summit before being blown downwind. The flux was found to be 100 +- 20 metric tons/day (t/d) for the three measurements possible before the wind shifted to the SW, making any measurements essentially oblique to the plume axis, and therefore of great uncertainty. An occasional strong odor of H₂S was detected at the camp during measurements.

During a crater visits on 29 and 31 August, and during a helicopter flight downwind in the plume, there was always a strong odor of H₂S. Under clear skies on 31 August the wind carried the plume SW, allowing stationary mode vertical and horizontal measurements. One specific goal of the research was to quantify the output of the isolated fumarole fields with different temperatures, which was possible for part of the day. Wind velocity was measured at 3 m/s and the SO₂ flux was calculated to be only 30 +- 10 t/d.

Kudriavy has been consistently degassing passively at high temperatures since at least 1961, when it was first visited by Russian scientists; annual fieldwork began in 1989. No change in activity was noted during this visit. At the low levels at which Kudriavy was found to be degassing, a realistic SO₂ norm may be 75 +- 50 t/d, with the oscillations potentially reflecting meteoric conditions. These low-pressure fumaroles, some with temperatures up to 950°C, produced hissing to roaring to deafening levels of noise. There was more noise and higher flux than at Momotombo (Nicaragua), where 950°C fumaroles were studied through the early to mid-1980s by U.S. and Russian collaboration.

Reference. Korzhinsky, M.A., Tkachenko, S.I., Shmulovich, K.I., Taran, Y.A., and Steinberg, G.S., 1994, Discovery of a pure rhenium mineral at Kudriavy volcano: Nature, v. 369, p. 51-52.

Information Contacts: Stanley N. Williams and Tobias P. Fischer, Geology Dept., Arizona State University, Tempe AZ 85287, USA; Kirill I. Shmulovich and Mikhail A. Korzhinsky, Inst. of Experimental Mineralogy, Russian Academy of Sciences, 142432 Chernogolovka, Moscow District, Russia; Genrikh S. Steinberg, Inst. of Volcanology & Geodynamic ANSRF, 693008 Yuzhno-Sakhalinsk, Box 18, Russia.

October 1999 (BGVN 24:10) Cite this Report

Small phreatic eruption from the Kudriavy summit forms a new crater

Changes in activity at the Kudriavy cone (figure 2) were detected in mid-September 1999, preceding an eruption on 7 October. Since 1989 the temperatures of sediments in the dry lakes within the crater (lakes temporarily exist after snow melting and strong rains) at a depth of 0.75 m have consistently fallen in the range of 48-82°C, with fluctuations of 3-5°C. In contrast, September 1999 measurements at the control points in the Hot Lake area showed increasing temperatures of 60-102°C. [These temperature measurements have been made 1-3 times each year.]

Figure 2. Photograph of fumarolic plumes rising from the crater of the Kudriavy cone at Medvezhia, September-October 1999. Courtesy of G.S. Steinberg.

The weather in August, September, and October was unusually dry for the region, with rain only during 24-25 September and 2-3 October. A temperature survey of two lakes was made in September. Usually, lakes exist 1-2 days after rains, but the water in Hot Lake still covered more than half the area on 4 October. Temperatures in the dry part of the lake had increased by 14-22°C. The lake water close to the hot dome was boiling and seething due to gas emissions. [The hot dome is 150-170 m in diameter, rising 60-70 m above the bottom of Hot Lake to the W and 30-40 m above the bottom of the dry lake to the S.] On 5 October the diameter of the lake was 15 m. That day two channels were excavated to allow the water to drain so that sediment temperatures could be measured. The temperature increase in this newly drained area was more than 30°C. Fumarole gas compositions during the second part of September showed increased hydrogen, oxygen, and fluorine. Sulfur ignition was seen in some locations. The number of earthquakes also increased, and although the one-channel seismic station deployed was insufficient to determine any hypocenters, the elevated seismicity was obvious. District and province authorities were warned three days before the start of the 7 October eruption that Kudriavy was unstable and could erupt soon. [On the evening of 4 October the Governor of Sakhalin and the Mayor of Kurilsk were notified that activity at Kudriavy had rapidly increased and that an eruption was expected to begin during the week of 8-15 October, with possible stronger activity later in the month.]

From the base camp, 3.5 km W from the volcano, black and gray clouds of gas and ash were observed rising above the usual fumarolic plumes at 1735 on 7 October and then extending ~10 km NW. Ejections of gas and ash occurred at intervals of 1-2 minutes. Because of the strong winds, maximum altitude of ejections was 1,100 m. The upper camp was at 940 m elevation, 30-40 m from the crater edge and 300 m from Hot Lake (figure 3). Because of strong winds, bad visibility, and the low-intensity start of the eruption, volcanic tremor and gas-and-ash ejections were not noticed in the upper camp until 10 minutes after observers in the base camp saw the plume. Night observations showed that intense ejections stopped at 0200 on 8 October. Observations through the clouds of the N part of the crater revealed "slight reddish lights - reflected light of the hot rocks and blue lights - light of the burning sulfur" that marked the edges of a crater.

Figure 3. Aerial photograph of the N part of the Kudriavy crater at Medvezhia showing the locations of the upper camp and the new explosion crater W of the hot lava dome during 7-8 October 1999. North is to the left. Courtesy of G.S. Steinberg.

No juvenile ash was identified, so the eruption was determined to be phreatic. This eruption was similar to a geyser eruption: periodic vertical ejection of the gas, ash, and steam. Ejecta didn't fall more than 30-40 m from the new crater. The surface of Hot Lake was covered by rocks with diameters of 20-30 cm, and ashfall deposits were concentrated to the NW. The volume of erupted material was nearly 40,000-45,000 m³. Areas with rhenium mineralization (see BGVN 20:10) located on the dome were not involved in the eruption or covered by eruption products. The first phase of the eruption was over on 13 October.

The eruption created a new crater in the Hot Lake area and removed part of the dome (figure 4). The crater was elliptical with dimensions of 30 x 40 m and a depth 35-40 m from the bottom of the lake and 80-110 m from the flat part of the dome (figure 5). The walls of the crater were vertical. In the lower part of the S crater wall was a 6 x 8 m cave of incandescent rocks. Based on the light intensity, the temperature was estimated to be higher than 1,000-1,100°C. Hot gas rose from this area and condensed 40-60 m above the edge of the crater. Small fiery areas and fragments with burning sulfur were seen on the S, W, and N walls. [Minor explosions continued from the cave until 13 October. Activity then declined, consisting of gas emissions with some small rock fragments that didn't reach the crater rim. No significant changes were noted through 2 November, when observations ended.]

Figure 4. Photograph of the hot dome and dry lake area in the N part of the Kudriavy crater at Medvezhia prior to the 7-8 October 1999 eruption. Courtesy of G.S. Steinberg.

Figure 5. Photograph of the 7-8 October 1999 crater adjacent to the hot dome in the N part of the Kudriavy crater at Medvezhia, October 1999. Courtesy of G.S. Steinberg.

Information Contacts: Genrikh S. Steinberg, Institute of Volcanology and Geodynamics, Russian Academy of Natural Science, Box 18, Yuzhno-Sakhalinsk 693008, Russia.