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Tolbachik

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  • Country
  • Subregion Name
  • Volcano Type
  • Last Known Eruption
  • 3682 m
    12077 ft
  • 55.830°
  • 160.330°
  • Elevation
  •  
  • Latitude
  • Longitude

5 June-11 June 2013

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 31 May-7 June that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the S fissure and weak gas-and-steam plumes were observed. A large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)



 Available Weekly Reports




2013: January | February | March | April | May | June |
2012: November | December |

5 June 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 31 May-7 June that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the S fissure and weak gas-and-steam plumes were observed. A large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

29 May 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 24-31 May that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the S fissure and weak gas-and-steam plumes were observed. A large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

22 May 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 17-24 May that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the S fissure and weak gas-and-steam plumes were observed. A large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

15 May 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 10-16 May that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the S fissure and gas-and-ash plumes were observed. A large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

8 May 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 3-10 May that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the S fissure and gas-and-ash plumes were observed. A large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

1 May 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 26 April-3 May that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the S fissure and gas-and-ash plumes were observed. A large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

24 April 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 19-26 April that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the S fissure. Gas-and-ash plumes rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted in multiple directions. A large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

17 April 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 12-19 April that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the S fissure. Gas-and-ash plumes rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted in multiple directions. A large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

10 April 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 5-12 April that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the S fissure. Gas-and-ash plumes rose to an altitude of 3.5 km (11,500 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. A weak thermal anomaly was detected over the crater of the volcano on 6 and 9 April. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

3 April 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 29 March-5 April that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the fissure. Gas-and-ash plumes rose to an altitude of 3.5 km (11,500 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

27 March 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 22-29 March that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the fissure. Gas-and-ash plumes rose to an altitude of 3.5 km (11,500 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

20 March 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 15-22 March that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the fissure. Gas-and-ash plumes rose to an altitude of 3.5 km (11,500 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

13 March 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 8-15 March that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the fissure. Gas-and-ash plumes rose to an altitude of 3.5 km (11,500 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

6 March 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 28 February-7 March that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the fissure. Gas-and-ash plumes rose to an altitude of 3.5 km (11,500 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

27 February 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 22 February-1 March that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow on the fissure. Gas-and-ash plumes rose to an altitude of 3.5 km (11,500 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

20 February 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 15-22 February that traveled to the W, S, and SE sides of the plateau. Four cinder cones continued to grow on the S fissure above Krasny cone. Gas-and-ash plumes rose to an altitude of 3.5 km (11,500 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

13 February 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 8-15 February that traveled to the W, S, and SE sides of the plateau. Four cinder cones continued to grow on the S fissure above Krasny cone. Gas-and-ash plumes rose to an altitude of 3.5 km (11,500 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

6 February 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 1-8 February that traveled to the W and S sides of the plateau. Four cinder cones continued to grow on the S fissure above Krasny cone. Gas-and-ash plumes rose to an altitude of 3.5 km (11,500 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

30 January 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 25 January-1 February that traveled to the W and S sides of Tolbachinsky Dol. Four cinder cones continued to grow on the S fissure above Krasny cone. Gas-and-ash plumes rose to an altitude of 3.5 km (11,500 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

23 January 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 18-25 January that traveled to the W and S sides of Tolbachinsky Dol. Four cinder cones continued to grow on the S fissure above Krasny cone. Gas-and-ash plumes rose to an altitude of 4 km (13,100 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

16 January 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 11-18 January that traveled to the W and S sides of Tolbachinsky Dol. Gas-and-ash plumes rose to an altitude of 4 km (13,100 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

9 January 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 4-15 January that traveled to the W and SE sides of Tolbachinsky Dol. Gas-and-ash plumes rose to an altitude of 4.5 km (14,800 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

2 January 2013              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 28 December-8 January. Strong seismicity was detected. Gas-and-ash plumes drifted in multiple directions, and a fifth cone continued to grow above the fissure. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Based on information from KVERT, the Tokyo VAAC reported that on 7 January an ash plume rose to altitudes of 3.7-4.3 km (12,000-14,000 ft) a.s.l. and drifted NE.

Sources: Tokyo Volcanic Ash Advisory Center (VAAC) , Kamchatkan Volcanic Eruption Response Team (KVERT)

26 December 2012              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 21-28 December. Strong seismicity was detected. Gas-and-ash plumes drifted in multiple directions, and a fifth cone continued to grow above the fissure. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

19 December 2012              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows that traveled 17-20 km during 17-21 December. Strong seismicity was detected. Gas-and-ash plumes drifted in multiple directions, and a fifth cone grew above the fissure. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

12 December 2012              Back to Top

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows that traveled 17-20 km during 7-17 December. Strong seismicity was detected. Ash plumes rose less than 1 km and drifted in multiple directions, and at least two cones grew above the fissure. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible in satellite imagery. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

5 December 2012              Back to Top

KVERT reported that the eruption from Tolbachik that began on 27 November continued through 8 December. A very large thermal anomaly on the N part of Tolbachinsky Dol, a lava plateau on the SW side of the volcano, was reported daily. Lava effused from two fissures along the W side of Tolbachinsky Dol; lava had flowed 17-20 km away from the S fissure by 7 December. Ash plumes rose less than 500 m during 1-5 December, and minor ashfall was reported in Kozyrevsk (40 km NW) and Klyuchi (65 km NW) villages on 3 December. Gas-and-steam plumes drifted 250 km SE on 5 December, and rose as high as 1 km during 7-11 December and drifted SW and W. The Aviation Color Code remained at Orange.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)

28 November 2012              Back to Top

KVERT reported that an eruption from Tolbachik that began on 27 November continued through 30 November. Lava effused from two fissures along the W side of Tolbachinsky Dol, a lava plateau on the SW side of the volcano, and ash plumes rose less than 500 m on 28 November. A large thermal anomaly was detected on the N part of Tolbachinsky Dol. On 29 November the Aviation Color Code was raised to Red. Ash plumes rose less than 500 m and drifted 300 km ESE. Later that day seismicity decreased and the Aviation Color Code was lowered to Orange. During 29 November-1 December Strombolian activity and lava effusion from two fissures continued. A large thermal anomaly continued to be detected in satellite imagery, and ashfall was reported in Kozyrevsk (40 km NW). According to a news article on 30 November, the lava flows destroyed two scientific base camps 10 km away. On 1 December gas-and-steam plumes with small amounts of ash rose over 400 m.

Based on information from UHPP (Yelizovo Airport), the Tokyo VAAC reported that ash plumes rose to altitudes of 4-6.1 km (13,000-20,000 ft) a.s.l. and drifted N and NW during 29-30 November and 3 December.

Sources: Tokyo Volcanic Ash Advisory Center (VAAC) , Kamchatkan Volcanic Eruption Response Team (KVERT)

21 November 2012              Back to Top

KVERT reported that episodes of volcanic tremor were detected in the area of Plosky Tolbachik during 7-10, 18, and 26 November. The number of shallow volcanic earthquakes increased to 250 on 26 November. A strong event occurred at 1652 on 27 November. The Aviation Color Code was raised to Yellow. That same day observers from Kozyrevsk (40 km NW) and Lazo (50 km SW) villages reported ash explosions and lava flows at Tolbachinsky Dol, in the same area as the 1975 eruption (northern vents). Ashfall, 4 cm thick, was reported in Krasny Yar (60 km NNW). The Aviation Color Code was raised to Orange. Based on information from the Kamchatka Branch of Geophysical Services (KGBS), the Tokyo VAAC reported that ash plumes possibly rose to altitudes of 6.1-10.1 km (20,000-33,000 ft) a.s.l. Ash plumes were not detected in satellite imagery. Plume altitudes were estimated based on seismic data.

Sources: Tokyo Volcanic Ash Advisory Center (VAAC) , Kamchatkan Volcanic Eruption Response Team (KVERT)



Summary of eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1975 Jun 28 1976 Dec 10 Confirmed 1 Historical South flank (18 & 28 km from summit)
[ 1973 Oct ] [ 1974 Dec ] Uncertain 1  
1970 Sep 1970 Dec 1 ± 30 days Confirmed 1 Historical
1970 Jan 1970 Apr Confirmed 1 Historical
1968 1969 Confirmed 1 Historical
1967 Oct 1967 Nov Confirmed 2 Historical
1967 Mar 1967 May Confirmed 2 Historical
1966 Apr 15 ± 45 days Unknown Confirmed 2 Historical
1965 Unknown Confirmed 1 Historical
1964 Mar 1964 Apr 24 (in or after) Confirmed 2 Historical
1962 Aug 1963 Confirmed 1 Historical
1961 Mar 24 1962 Feb 16 (in or after) Confirmed 2 Historical
1959 1960 Confirmed 2 Historical
1958 Jul 13 (in or before) Unknown Confirmed 2 Historical
1956 Sep 28 1957 Nov 28 Confirmed 2 Historical
1955 Oct 6 1955 Dec 8 Confirmed 2 Historical
1955 Jan 7 1955 Feb 9 Confirmed 2 Historical
1954 Feb 21 1954 Jun 13 Confirmed 2 Historical
1947 Jan Unknown Confirmed 2 Historical
1940 Nov 1941 Jul 15 ± 45 days Confirmed 2 Historical Summit, SW flank (1950 m)
1940 Feb 1940 Apr Confirmed 2 Historical
1939 Sep 25 1939 Sep 27 Confirmed 2 Historical
1936 Aug 13 (in or before) 1937 Mar 2 Confirmed 2 Historical
1931 Mar 4 1932 Confirmed 2 Historical
1904 Unknown Confirmed 2 Historical
1793 Unknown Confirmed 2 Historical
1790 Unknown Confirmed 2 Historical
1789 Unknown Confirmed 2 Historical
1788 Unknown Confirmed 2 Historical
1769 Feb 15 ± 45 days 1769 Oct 15 ± 45 days Confirmed 2 Historical
1740 Dec Unknown Confirmed 2 Historical
1739 Feb 1 ± 30 days Unknown Confirmed 2 Historical
[ 1699 ± 1 years ] [ Unknown ] Uncertain 2  
1550 (?) Unknown Confirmed 2 Tephrochronology SW flank (Zvezda)
1050 (?) Unknown Confirmed 3 Tephrochronology SW flank (Visokaya, Treschina)
1000 (?) Unknown Confirmed 4 Tephrochronology SW flank (Kleshnya, Rastaschenny)
950 (?) Unknown Confirmed 4 Tephrochronology SW flank (Alaid)
900 (?) Unknown Confirmed 4 Tephrochronology SW flank (Peschanie Gorky)
550 (?) Unknown Confirmed 3 Tephrochronology SW flank (Kamenistaya)
450 (?) Unknown Confirmed 3 Tephrochronology SW flank (Dvoinoy, Nedostupny, Dalny)
400 (?) Unknown Confirmed 4 Tephrochronology SW flank (Pelmen, Lagerny)
350 (?) Unknown Confirmed   Tephrochronology SW flank (Zasipannie)
250 (?) Unknown Confirmed   Tephrochronology SW flank (Poteryanny, Yupiter)
150 (?) Unknown Confirmed   Tephrochronology SW flank (Zapretny)
50 (?) Unknown Confirmed 4 Tephrochronology SW flank (Mt. 1004, Pra-Visokaya)
100 BCE (?) Unknown Confirmed   Tephrochronology SW flank (Sosed, Malenky)
200 BCE (?) Unknown Confirmed   Tephrochronology SW flank (Kust)
700 BCE (?) Unknown Confirmed   Tephrochronology SW flank (Buraya)
750 BCE (?) Unknown Confirmed   Tephrochronology SW flank (Tsepochka, Malishi)
800 BCE (?) Unknown Confirmed   Tephrochronology SW flank (Serga, Starichky)
1650 BCE (?) Unknown Confirmed   Tephrochronology SW flank (Istochniky)
1750 BCE (?) Unknown Confirmed 3 Tephrochronology SW flank (Mokhnataya)
2050 BCE (?) Unknown Confirmed 3 Tephrochronology SW flank (Kruglenky)
4550 BCE (?) Unknown Confirmed   Tephrochronology Plosky and Ostry Tolbachik calderas
5450 BCE (?) Unknown Confirmed   Tephrochronology SW flank and NE flank
5600 BCE (?) Unknown Confirmed   Tephrochronology SW flank
5650 BCE (?) Unknown Confirmed   Tephrochronology SW flank (Bubochka)
6050 BCE (?) Unknown Confirmed   Radiocarbon (uncorrected) SW flank (Lesnaya)
7600 BCE Unknown Confirmed   Radiocarbon (corrected)

The massive Tolbachik basaltic volcano is located at the southern end of the dominantly andesitic Kliuchevskaya volcano group. The Tolbachik massif is composed of two overlapping, but morphologically dissimilar volcanoes. The flat-topped Plosky Tolbachik shield volcano with its nested Holocene Hawaiian-type calderas up to 3 km in diameter is located east of the older and higher sharp-topped Ostry Tolbachik stratovolcano. The summit caldera at Plosky Tolbachik was formed in association with major lava effusion about 6500 years ago and simultaneously with a major southward-directed sector collapse of Ostry Tolbachik volcano. Lengthy rift zones extending NE and SSW of the volcano have erupted voluminous basaltic lava flows during the Holocene, with activity during the past two thousand years being confined to the narrow axial zone of the rifts. The 1975-76 eruption originating from the SSW-flank fissure system and the summit was the largest historical basaltic eruption in Kamchatka.