Kamchatka is one of the most remote parts of the world with difficult access to most of its volcanoes. And yet, there are detailed maps available, and many of the volcanoes are researched well. Have you ever wondered how on earth volcanologists figure out the volume of a crater lake or the size of a lava flow in a remote volcano? No, they don’t go out with a folding meter stick: In the second part of this post I’ll have a look at photogrammetry, a very important way of monitoring volcanoes in Kamchatka (and elsewhere). But first I’ll introduce you to Maly Semyachik, who we have heard of lately by KVERT when they set its aviation code to Yellow.
The Kamchatka Peninsula in far eastern Russia is one of the most active arc segments on Earth, with the largest number of collapse calderas per unit of arc length and high magma and volatile output rates. Maly Semiachik (Малый Семячик – Little Semyachik; also Maly Semliachik or Srezannaya mountain) is located in the southern central part of the Eastern Volcanic Belt of Kamchatka. Geographically the volcano is located 20 km W of the shore of Kronotsky Bay, 15 km NE of Karymsky volcano and 140 km NE of the city of Petropavlovsk-Kamchatsky.
The volcano lies on the northwestern periphery of the large (55 x 65 km) Karymsky Caldera Center which involves several calderas. Maly Semyachik’s own ~7km wide caldera lies within the 15 x 20 km mid-Pleistocene Stena-Soboliny caldera. Field studies have identified an ignimbrite of 200 m thickness to be associated with this caldera. It is likely composed of two to four individual units, which are densely welded at the bottom and more pumiceous at the top, and all are dacitic–andesitic in composition. Its likely age is 1.13 Ma.
Recent studies found a possible inverse correlation between the activity of Maly Semyachik and Karymsky volcanoes. This may imply a common deep magma source between the two. (The Karymsky Caldera Center warrants a long and interesting post of its own, we’ll do that later.)
Maly Semyachik itself is composed of three overlapping stratovolcanoes along a NW-SE fault: Paleo-Semyachik (20 ka), Mezo-Semyachik (12 ka) and Ceno-Semyachik (8.1 ka). In the NE of the ridge-shaped massif is the highest and oldest Main Peak (Paleo S., 1553 m). It has a flat summit and is torn in the west by a semi-annular fault.
Video: This 5-minute YT video by Eugene Potapov shows detailed crater views of Maly Semyachik. (In the accompanying text the authors warned tourists to be wary and stay away from greedy tour operator companies: They were denied their – prepaid – flight back from the volcano and had to bribe the pilots in order to secure their seats. Now this was 10 years ago, hopefully things have improved since.)
The activity of the youngest (Ceno-S.) began with dominantly explosive eruptions, constructing the present cone. A second stage began about 4,4 ka; during that period the volcano was destroyed by major explosions and reconstructed again. Its crater, called Troitsky or No. VI crater, very probably formed due to collapse-subsidence processes (as opposed to a large explosive eruption) some 400 years ago.
The crater lake was established in the first half of the 20th century inside the already existing crater. It is now ~300m wide and filled by an acidic warm lake, Zelyonoe Ozero (Green Lake) with a pH less than 0.5. Maly Semyachik has erupted high-aluminium basalts, andesite-basalts, andesites and some dacites in the past. At present, eruptions – if any – would be expected to be of phreatic nature. Possible hazards are thermal explosive eruptions which produce ash plumes, ash falls, pyroclastic flows and lahars.
The GVP lists 23 Holocene eruptive periods. Only five of them are historical observations, from 1804 on, all VEI 2s and a VEI 3. The last confirmed eruption was in 1952. A carbon-dated eruption that probably took place in ~1550 was larger with a VEI of 4.
Going through the archive of Tokyo VAAC advisories (back to 2006) I found two more recent eruptions not mentioned anywhere else:
– On 29 Dec 2010 at 05:18 UTC an eruption from Maly Semyachik is reported at FL200.
– On 07 July 2017 at 06:40 UTC a small ash eruption from Maly S. at FL070. (Apparently, the reported ash cloud reached an altitude of 2.1 km a.s.l., or 600 m above summit. – I wonder if perhaps an eruption of nearby Karymsky could be the culprit instead? Because it had a thermal anomaly reported by KVERT on that very day, and Maly S. was not mentioned by them at all.)
KVERT has raised the volcanic alert level of Maly Semyachik on 22 March 2018 to Yellow. The reason was an early and very fast melting of the ice that covers the lake over winter. Within ten days the major part of the lake had become ice-free, while the surrounding slopes didn’t show signs of thawing (image above). This meant at least a substantial rise in lake temperature.
Unfortunately I have not found any more-detailed reports on Maly S.’s activity than the usual brief notes like these:
22/03/2018: An activity of the volcano increased. Satellite data by KVERT showed a thermal anomaly over the volcano on 20-22 March. It is assumed that the ice cover of the lake has melted. Explosive activity of the volcano is possible.
13/04/2018: An activity of the volcano continues. Satellite data by KVERT showed a thermal anomaly over the volcano on 06 and 11 April, the volcano was obscured by clouds in the other days of week.
17/04/2018: An activity of the volcano continues. Satellite data by KVERT showed a weak thermal anomaly over the volcano.
So it remains anyone’s guess as to what exactly the activity consists of.
Nowadays in geological research there is a plethora of modern methods like GPS, radiography, magnetometry, InSAR, LIDAR etc.. They are also used by volcanologists to research volcanic processes and forecast volcanic eruptions. Among them is one that is sometimes looked down upon, like, bah, anybody can take pictures and compare them… Photogrammetry plays an important role in researching Kamchatkan volcanoes – not last in forecasting an eruption of Maly Semyachik.
Since 2008, the calculation of quantitative characteristics of eruptions, mapping, and 3-D modelling are based on the results from digital photogrammetric processing using various software. The calculating error for an eruption volume is usually less than 1%. I’ll give you just a short glimpse at this new-but-not-so-new method (mainly based on: “Photogrammetric Survey in Volcanology: […]”, Viktor Dvigalo et al., 2016).
Photogrammetry is a research tool that combines optics, mathematics, and photography to achieve an overall picture of our object. The method comes in handy in cases when it is easier to take a photograph than to measure directly. Among others, it is used for consistently monitoring short-term changes in the shape of volcanic structures and for obtaining accurate parameters of eruptions, like lava flow speed and ash output.
It is a 3-dimensional coordinate measuring technique that uses photographs as the basis for measurements. Photogrammetry requires preparatory fieldwork, which is the most laborious and expensive part: Ground targets need to be placed on the surface of the object so that they can later be easily identified in the photos. Their coordinates are then defined for geodetic reference. The fundamental principle used by Photogrammetry is triangulation. By taking photographs from at least two different locations, so-called “lines of sight” can be developed from each camera location to points on the object. These lines of sight are then mathematically intersected to produce the 3-dimensional coordinates.
Historical use in Kamchatka
Photogrammetry has been used to study active volcanoes in Kamchatka for more than 100 years. The first were N. G. Kell et al. in the Kamchatka expedition of the Russian Geographical Society in 1908–1910. In 1908, the expedition first used conventional cameras. Later they constructed a “photogrammeter” using an Ernemann camera, parts from a surveyor’s table, and an alidade (turning board). In 1910, a Laussedat phototheodolite was used for a panoramic photogrammetric survey. The investigation resulted in about 2000 single photographs and stereo pairs of almost all of the active volcanoes and many of the dormant ones.
A new age in photogrammetry began in 1973 when reference geodetic networks on the most active Kamchatkan volcanoes were established, and quality large-scale topographic plans and maps were plotted. These became the theoretical basis for the future photogrammetric investigation of volcanoes. For aerial photography, the scientists used USSR analogue aerial photogrammetric cameras and Carl Zeiss Jena phototheodolites. A Carl Zeiss Jena stereocomparator, a Romanovsky stereoprojector, and a coordinatograph were aquired for photogrammetric processing.
In 1984, the Institute of Volcanology bought a whole set of state-of-the-art equipment from Carl Zeiss Jena (I’m sure they didn’t have to pay “that much” – between friends 😉 – as Carl Zeiss Jena was in the German Democratic Republic). For the next 23 years this equipment enabled detailed research on surface changes and the calculation of quantitative characteristics of eruptions. For the first time, morphological precursors of volcanic activity were revealed for the most frequently surveyed volcanoes like Klyuchevskoy, Shiveluch, Bezymianny, and Maly Semyachik.
And what has this to do with Maly Semyachik? Two examples
1. Photogrammetric investigation of new and archived photos allowed for a detailed analysis of Troitsky Crater and Zelyonoe Lake. The analysis of aerial photographs showed constant landslides and crumbling on the inner walls of Troitsky Crater. Material fell into the lake, affected its bed morphology and thus its surface level.
From the photogrammetrically measured volumes of the above-water part of the crater the scientists deducted a difference of 1.5 Mill. m³. This was the amount of scree deposited on the crater bottom during the previous 44 years. During that time the water level rose 37 m, which corresponded to a volume increase of 9 Mill. m³. Therefore, the bulk of scree material for 44 years accounted for 17% of the lake volume gain. As the scree was of a very crumbly nature, it would take up less volume in the lake than, say, boulders. So its contribution to the overall volume gain of water was determined to be ~10%.
Based on these findings, a graph of the lake water level for the period from 1946 to 2012 was plotted. It showed that the moderate increase of the water level – 0.9 m per year – since 1950 had been accompanied by a rapid increase of the water level related to volcanic unrest. Over the 1968–1971 period, the water level rose by 13 m, and over the 1981–1986 period another 8.7 m. Those were periods of high volcanic activity.
2. The images of 2 June 1986 showed distinct concentric turbid spots on the surface of the crater lake. The size of these spots varied from image to image within one aerial pass, which is evidence for the rapid movement of water masses. This indicated an upcoming eruption! The fact was then proven during fieldwork in Aug./Sept. that year. For the first time, aerial photogrammetric surveys had proven successful for an eruption forecast for this volcano.
And elsewhere in the world:
Digital models of the earth’s surface can record minute changes around volcanoes, down to fractions of a second before, during and after an eruption. As an example, here is a demo video taken on Santa Maria volcano, Guatemala. The researchers used ground-based photogrammetry and structure from motion (SfM) method. Produced 2016 by Brett B. Carr of Arizona State University:
Another example of how accurately volcanic processes can be figured out is this 2018 study: Scientists used photogrammetry to create multiple DEMs (Digital Elevation Models) of the 2013 Sinabung lava flow:
Sept 22, 2014: volume of the lava flow was 1.03 ± 0.14 × 10^8 m³ (0.1 km³).
Jan 10 – Sept 22, 2014: the average effusion rate was 4.8 ± 0.6 m³/s.
Flow inflation caused it to overtop confining ridges, leading to instabilities. Sept 2014: flow front advance was 3–11 m/d, isolated to a few breakout lobes.
With the use of drones, thermal cameras and ever more sophisticated modelling software it seems that soon we’ll just have to gaze deeply into a volcano’s eye to find out what he is up to in the future 😉
Disclaimer: I am not a scientist, all information in this (and any of my other posts) is gleaned from the www and/or from books I have read, so hopefully from people who do get things right! 🙂 If you find something not quite right, or if you can add some more interesting stuff, please leave a comment.
Enjoy! – GRANYIA
SOURCES & FURTHER READING
– GVP, Maly Semyachik
– Large-volume silicic volcanism in Kamchatka:[…] (2009, PDF)
– Photogrammetric Survey in Volcanology:[…] (2016)
– Deformation patterns, magma supply and storage at Karymsky VC, InSAR (2018, paywalled)
– KVERT: Active Volcanoes of Kamchatka
– Rapid, low-cost photogrammetry […] Mt. St. Helens (2011, paywalled)
– Nim Xkanul: Reporting Volcanism in Guatemala
– Emplacement of the active lava flow at Sinabung […] (2018, paywalled)