Picture the scene: an intrepid 19th Century Russian cartographic team is exploring the wilds of the Kamchatka peninsula, driven by a desire to map and record every feature. Armed with instruments and drawing boards they set up camp in the central valley. As they survey the mountains around them they point to one and ask their local guide, “And what is that one called?” The local man answers them with a ‘who cares’ shrug – it’s just a meaningless medium-sized mountain where nothing has ever happened. “I don’t know,” he says, and shuffles off. And so, because every feature must have a label, it is recorded on their map as ‘Bezymianny’ – ‘without a name’.
OK, that’s a flight of fantasy driven by schoolboy tales of when British explorers set out around the world. Lake Nyasa, for instance, almost certainly received its name in similar fashion. “What’s the name of this?” asks David Livingstone. “Nyasa!” reply the bemused locals, giving their language’s word for ‘a lake’. (In my imagination they answered along the lines of, “Duh, what’s it look like. It’s a lake, mate. Are you thick or what?” – and before anyone mentions it, the story of “kangaroo” being Aboriginal for “I don’t know” is not true!)
In truth I do not know how Bezymianny came to get its ‘name’, but it is perhaps understandable that it was overlooked, as it is overshadowed by its giant near-neighbours, Kamen and Kliuchevskoy. At 4835 m Kliuchevskoy is Asia’s tallest volcano, and also one of the most active. Over 6,000 years it has built itself into a frighteningly beautiful edifice of near-perfect conical proportions – every schoolchild’s idea of a volcano. Kamen stands 4585 m tall, although it was probably once even higher. Around 1,200 years ago it suffered a catastrophic flank collapse, but has lain dormant since around that time.
These two, along with Ushkovsky/Plovsky and Bezymianny, are the main features of the Kliuchevskaya group in central Kamchatka. This is a classic subduction volcanic area, its andesitic magmas produced as a result of the diving of the Pacific plate under the Okhotsk plate where they meet some 200 km to the east.
According to the GVP http://www.volcano.si.edu/world/volcano.cfm?vnum=1000-25= Bezymianny ‘was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral volcano [Pra Bezymianny] that was built between about 11,000-7000 years ago.’ There were periods of activity around 4,700, 3,500 and 2,500 years ago, the latter a VEI 4 event. Sporadic events continued until around the year 950, when another VEI 4 brought activity to a halt, at least on a human timescale.
For the next thousand years the ‘nameless’ mountain slept. It had reached a height of 3085 m, and was a fairly typical stratovolcano formation of andesitic rock.
At the end of September 1955 a swarm of earthquakes began underneath Bezymianny. They were recorded by a series of seismographs that had been installed by the Soviets in the late 1940s, primarily to observe the nearby and highly active Kliuchevskoy. A volcanic observatory had already been established at the village of Klyuchi in 1935.
After 23 days of earthquakes Bezymianny began erupting on 22 October with a series of explosive events. A crater of around 800 m diameter formed at the top, and a dome began to build in the crater as the eruption continued into November. On 22 January a worrying sign was spotted by observers in an aircraft: the southeastern flank of the mountain was beginning to bulge outwards. At the same time, analysis of photographs showed that the cone in that area was uplifting as magma intruded into a cryptodome.
In early 1956 seismic and eruptive activity began to decrease as internal pressure increased, the bulge continued to grow and the southeast section of the cone continued to lift. By late March it was estimated to have reached 100 m of deformation.
On the 30th of the month the inevitable happened. At around 17:05 an estimated 0.5 km3 of the eastern flank collapsed and the side of the mountain came crashing down. As the structure failed, it released the monumental pressure that had built up inside, fed by gas-rich magma from the bulging cryptodome.
As the mountain’s side slipped away, forming a devastating avalanche of rock, a cataclysmic blast blew out towards the east, flattening trees more up to 25 km away and spreading blast deposits out to more than 30 km. Following the blast Bezymianny continued to erupt violently, creating an ash plume that reached an altitude of nearly 40 km. Pyroclastic flows surged eastwards, following the rubble avalanche from the flank collapse. Subsequently lahars formed in the waterways at lower elevations.
Does this sound a bit familiar? It should do, for the 1956 Bezymianny blast was mirrored in many ways by that of Mt St Helens in May 1980. Subsequent research at both sites has shown that the deposits produced by these directed blast surges are very similar – and unlike any others found elsewhere. Stratigraphy showed typical deposits of pre-climactic ash, overlaid with flank collapse debris, above which were directed blast deposits, and finally pyroclastic surge and fallout deposits on top.
Bezymianny’s awakening was classed as a VEI 5 event, and produced an estimated 2.8 km3 of tephra. It left a giant crater in the side of the mountain measuring 1.3 x 2.8 km. Thanks to the sparsely populated terrain of Kamchatka, there were no recorded fatalities.
Bezymianny’s first eruption for a millennium continued for another year before coming to a halt on 1 March 1957. By then, however, there were clear signs that the volcano was not going to sleep. In the vast crater left behind by the flank collapse and directed blast, a dome had begun to grow in the weeks after the blast. This became the centre of activity for the volcano as it rose from the ashes of its cataclysmic collapse.
For observers the wait for further dome-building events was not long, a small explosive/eruptive event occurring on 31 July. Since then the mountain has been highly active, erupting over 50 times. The most recent event occurred in March 2012.
Most of the eruptions have been small explosive events accompanied by varying degrees of lava extrusion and pyroclastic surges. Some have lasted for a day or two, others for months. In the early years solid obelisks were extruded, along with fine ash.
Since 1965 activity has been concentrated at the vent in the upper part of the dome and plastic lava has become more of a feature as the viscosity of the magma has gradually reduced over time. From around this time the larger explosive events also caused portions of the upper dome to collapse in their early stages, although subsequent lava extrusions have generally ‘healed the wounds’. The most explosive event since the 1956 eruption occurred in 1985, and produced a smaller directed blast surge triggered by a partial dome collapse. In this case the pyroclastic flows reached a distance of 12.5 km.
The topographical effect of these events has been to build up the central cone, which was christened simply ‘Novy’ (‘new’ – these Russians sure have a vivid imagination when it comes to naming). In fifty-plus years the rise of Novy has been nothing short of spectacular, and it now almost fills the area of the crater left behind after the 1956 blast. Photographs provide a graphic illustration of the growth of the cone.
Novy now stands at 2882 m, not far short of Bezymianny’s pre-1956 level. The height of the central cone has long surpassed that of the crater walls in which it has grown. If the ongoing eruptions continue, Bezymianny will have soon built itself back up to the size it was before the blast.
What happens now? The short answer, of course, is that no-one knows. Bezymianny could continue to grow past its original size into a Kliuchevskoy-like monster. However, just a look at the photographs of the steep-sided Novy cone, supported to an extent on three sides by the old crater but open to the east, and it is easy to imagine that another major flank collapse could occur at any time.
Bezymianny’s explosive potential – and its uncanny similarities to Mount St Helens (with its own slower-growing dome) – make it one of the most watched volcanoes in the world, especially since a comprehensive system of seismometers and GPS instruments was installed after a sizeable event in 2006. These allow the detailed monitoring of quakes and tremor, and also the development of any deformities. The volcano is routinely monitored from space to show up thermal anomalies on the surface, which have proven to be a good indicator of imminent activity.
Both Russian and US scientists are watching closely – what is happening to Bezymianny in double-quick time today could very well be the destiny of the more dangerously located Mount St Helens, albeit over a more leisurely timescale.
Acknowledgment: I would like to extend a special thanks to Alexander Belousov at the IVS in Petropavlovsk, who has kindly given permission for his photos to be used. Papers that he co-authored with Marina Belousova and other colleagues also provided much of the information for this short article. For those who may be interested in the deeper ‘science’ bit, notably the examination and research of Bezymianny’s pyroclastic deposits, many of the papers can be viewed at: http://www.kscnet.ru/ivs/lavdi/staff/belousov/litinter.html#public For current photos, webcams and information on Bezymianny and other Kamchatkan volcanoes, see KVERT at http://www.kscnet.ru/ivs/kvert/index_eng.php
*I must state that, in terms of volcanology, I am still in infant’s school, and I stand in awe at the level of information presented here by many of the contributors. However, the recent activity at Bezymianny led me to read up some more about this volcano, and would like to have a go at sharing my fascination. What grabs my interest the most is the rapidity with which the volcano has rebuilt itself. The volcanic processes that are ongoing often take centuries or longer, but such is the level of activity that in Bezymianny’s case the process has been witnessed over a matter of decades, and can be visualized through photographs – no imagination necessary!