I first ran across Sarychev Peak via the spectacular photos taken of its June 12, 2009 eruption by astronauts in the International Space Station (ISS) almost a decade ago. Serendipitous timing of this pass was almost perfect, as it showed the rapidly growing eruptive plume and at least three pyroclastic flows from the main vent as the plume started to top out. The still photos during the overflight have been made into a variety of videos. I think the following one is the most powerful and shows the 3-D nature of the plume nicely.
Sarychev Peak is one of the most active stratovolcanoes of the Kuril Islands. It is the NW end of Matua Island in the central Kurils. The volcano is an andesite / basaltic andesite volcano. The island is uninhabited in a sparsely populated region, with only 148 people within 100 km of it. Though it does get visitors on an irregular basis.
Matua Island is a volcanic island in the center of the Kuril Island chain. Over the centuries, Japan and Russia (Soviet Union) have made multiple claims to it and ownership has transferred based on the winner of the last armed conflict. Currently, Russia owns it. The name in the Ainu language means “hellmouth.”
Initial European discovery in 1644 showed it as part of feudal Japan. Some early European documents refer to the island as Raukoke. There was a Japanese airfield and garrison on the island during WWII. The Soviets seized the island in August 1945 and manned the formerly Japanese facilities until the dissolution of the Soviet Union in 1991. The island is currently uninhabited though does get periodic scientific and tourist visits.
Climate is subarctic, with heavy precipitation, clouds and fog. It is also much colder than similarly situated Manchurian locales.
The island itself is 52 km2 in area, with the highest point being one side of Sarychev’s crater at nearly 1,500 m. The volcano is also known as Fue-san, Matsuwa-jima, Matua-jima, and Sarnicheff.
Sarychev Peak is monitored by the Kamchatka Volcanic Eruption Response Team (KVERT) and Sakhalin Volcanic Eruption Response Team (SVERT). Most recent activity detected are thermal anomalies via satellite sensing on 15 Oct 2018. It was carried the end of October as Aviation Color Code of orange. https://volcano.si.edu/volcano.cfm?vn=290240
The Tokyo Volcanic Ash Advisory Center (VAAC) is responsible for monitoring and issuing ash warnings for Kuril Islands volcanoes. Due to the weather in this part of the world, monitoring depends heavily on remote sensing (satellite) methods. https://ds.data.jma.go.jp/svd/vaac/data/index.html
Matua Island is elliptical roughly 6 x 12 km, with the long axis pointing toward the incoming Pacific Plate. Most of the island is covered by volcanic rocks. 2 km2 of the island are marine sediments. The SE end of the island is mostly flat with a 40 – 60 m cliff around the flat plain. The northern end of the island is dominated by the volcanic peak.
The ancestral Matua Volcano is a somma of an ancient caldera, which would make Sarychev an intracaldera stratovolcano. The active Sarychev Peak grew in two stages, the oldest being primarily andesitic, and the last 500 years being basaltic andesite. The oldest eruptive centers are thought to be within the Matua Volcano caldera. Volcanic activity during the andesitic stage was highly explosive with around 40 known eruptions, including at least 4 catastrophic eruptions. The newer Sarychev Peak has been active since the most recent caldera forming eruption. It is dated based on underlying soils buried by scoria layers.
Chemistry of the erupted products is similar to those of Indian Ocean basalts. Tephras from Matua Island are similar in composition to recent lavas from Sarychev Peak.
Sarychev Peak has multiple eruptions since its discovery by Europeans, with 19 known eruptions since 1765, 16 of them since 1923. Eruptions are typically in the VEI 2 – 4 range. The June 11, 2009 eruption was a VEI 4 and took place after 33 years of inactivity. Historic eruptions range between effusive, lava flow creating eruptions and Plinian explosions with significant pyroclastic and ash emissions.
The June 12, 2009 eruption was one of the largest historical eruptions in the Kurils. The explosive portion of the eruption lasted 11 – 16 June. The explosion June 12 put a plume 16 – 21 km into the air. This plume disrupted international air traffic in the western Pacific for a while. Large amounts of SO2 aerosols were erupted 15 – 16 June. Weak explosions continued after June 16, and a field team on the island 26 – 28 June did not observe any eruptive activity.
There were at least 23 separate explosions 11 – 16 June. Volcanic ash and aerosols made it a long way from the volcano, up to 1,500 km to the N and NW and as far as 3,000 km to the SE. Sarychev dusted Sakhalin Island to the NE for the first time in recorded history. SO2 aerosols were tracked as far as Greenland before they started being removed from the stratosphere.
The volcano was dormant with substantial fumarole activity before the eruption. Visitors in August 2008 visited the crater and heard noises. The weather was foggy at the time so they were not able to see anything during the visit. Increased gas emissions were documented in June 2009. Initial warning of the June 11 – 16 sequence was a minor thermal anomaly and weak ash plume. A research ship passing by the island the evening of June 11 did not notice any eruption.
A nicely and completely unintentionally timed ISS pass collected photos of the eruptive plume punching its way through the clouds surrounding the island on June 12. Holes in cloud covers over Kuril Islands are not uncommon and thought to be caused by wet air being forced upwards, where the clouds evaporate, leaving a hole in the cloud deck. There is an alternate theory that the hold was caused by the shock wave generated by the eruptive plume and its propagation though the troposphere. A third explanation is that as the plume rises, air flows down around its sides. As the air sinks, it tends to warm and evaporate existing clouds. Scientific disagreement about the cause of the hole in the cloud continues.
There were 29 still images taken during the flyover. These have been combined into videos which show the 3-D nature of the plume above the volcano.
The top of the plume is called a pileus cloud, water condensation caused by rapid rising and cooling of the air mass above the cloud. At this point, the plume is about to punch its way through the pilus cloud.
Pyroclastic flows from this eruption added 1.4 km2 to the island and extended out into the sea. A year after the eruption, 0.19 km2 of the island had been removed by erosion. Pyroclastic flows were initially thought to have covered over 8 km2. This was increased to 25 km2 following a survey a year after the eruption. Minimum eruptive volume is estimated at 0.4 km3. There were at least eight of these flows, mostly on the northern and western flanks of the volcano. Visible thickness of the flows vary 1 – 4 m. All are basaltic andesites. There were lahars during the early part of the eruption.
There was continuing activity 16 – 28 June, generally gas and steam emission plumes. There were four thermal anomalies detected Nov 2009 – May 2010 and a small ash plume in Sept 2010. This eruption also emitted a pair of lava flows extending around 2.5 km from the summit crater. The new flows covered 0.8 km2.
The most recent activity reported by Tokyo VAAC on 15 Oct 2018 was a 2 km ash plume that drifted as far as 65 – 70 km from the volcano.
There was an earlier thermal anomaly visible via satellite on 22 Sept 2018. This series of eruptions began 11 Sept and continued through 21 Sept. Ash plumes in the 4 – 5 km range were erupted during the middle of this date range, and traveled as far as 120 km.
There was a period of weak steam and gas emissions and thermal anomalies Oct – Nov 2017.
The 2009, 1946, 1930 and 1765 eruptions were among the largest observed from Sarychev Peak.
The volcanic ash and aerosol plume from the 2009 eruption was among the most closely studied plumes in recent history. Several papers discussed what they call “… a pattern of discrepancies between stratospheric aerosol data from the OSIRIS instrument, other measurements, and model simulations…’ of volcanic plumes from Kasatochi (August 2008), Sarychev Peak (Juln 2009), and Nabro (June 2011).
The two discrepancies are a lag in aerosol onset and a low bias in maximum stratospheric aerosol optical depth by the OSIRIS instrument. In other words, it appears to be reporting stratospheric aerosol arrival late and at a lower altitude in the atmosphere than the aerosols actually are located.
This showed up in analysis of the 2011 Nabro plume of SO2 aerosols which was initially thought to be confined to the troposphere. Analysis of these plumes by other sensors suggest there was a larger volume of aerosols injected higher into the atmosphere by these three eruptions than OSIRIS reported. A 2014 paper by Fromm, et al did the analysis and proposed a correction to OSIRIS data to bring it in line with what other sensors are reporting. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014JD021507
The discrepancies showed up in analysis of the Kasatochi and Sarychev eruptions both of which injected plumes directly into the stratosphere. It was not until analysis of the Nabro eruption that sufficient data was available to figure out what the problem was and propose a correction. This is an example of continuous refinement of what we are seeing with our instrumentation.
The Kuril Island system formed starting some 30 Ma by the subduction of the Pacific Plate under the Okhotsk Plate. The Kuril – Kamchatka Trench is offshore to the east. Convergence rate is 8.6 cm/year. Age of the oceanic crust being subducted is 90 – 118 Ma. Massive earthquakes along the Kurils can be quite deep, up to 650 km. There have been 10 Great Earthquakes along this subduction zone since 1923 ranging M 7.8 (2017) – 9.0 (1952).
The volcanic arc is divided into zones or sectors – northern, central and southern. The depth of the subducting plate under the volcanic arc is 100 – 106 km. Crust thickness varies from 25 – 36 km, with the thicker crust on either end and thinnest in the middle. There are over a hundred volcanoes in the Kurils, with 39 of them recently active.
The back arc Kuril Basin started forming some 23 – 9 Ma. Magmatic processes in the basin remained active until 1 Ma.
There are lithospheric blocks underlying the Kuril Islands. The northern block seems to be a bit hotter than the southern one. Matua Island lies near the proposed boundary between the blocks. There was a chemical change in the lifetime of the system, taking place around the time of the caldera-forming event that Sarychev Peak started building after. This change may be due to a change in the depth of the subducting plate under Matua Island.
This change has also been described for three volcanoes in southern Kamchaka and tied to the change of the Kuril – Kamchatka island arc from extension in the rear zone (Okhotsk Basin) to compression. It also shows up in Alaid Volcano.
Sarychev Peak is a young, highly active Kuril volcano. It occupies a somma following the most recent catastrophic eruption of Mount Matua. Its 2009 eruption after 33 years of inactivity killed most plant life on the uninhabited island and increased its size via deposition of multiple pyroclastic flows. Follow-on lahars and erosion started shaving the new island back into the sea. It appears to have a significant and active magma source. Probably a good thing the island remains uninhabited at this time.