Sarychev Peak Update for 6/18/2009

Sarychev Peak erupting on June 12th. Image taken on the ISS, courtesy of the NASA EO.

The eruption as Sarychev Peak seems to be waning a bit, at least according to some of the latest images from the NASA Earth Observatory's collection of MODIS shots. The ash plume is less prominent - and strikingly more grey than before, possibly if it contains a higher proportion of water vapor than the earlier plumes. However, it isn't these brand new shots that captured my attention but rather one of the possibly most stunning volcano images I've seen in years (above). This captures Sarychev Peak as a rare clear view appeared to the volcano through the clouds and we can see the ash column and pyroclastic flows moving down the flanks of the volcano. The image was taken from the ISS by one of the astronauts currently on the station and really, I am almost at a loss for words about how amazing this picture is.

The eruption is still diverting aircraft to a number of cities, including San Francisco, Anchorage and Seattle as flights to/from Asia need to refuel after/before taking the long route around the ash plume. I haven't seen any real word on how disruptive this eruption has been to worldwide aviation, but I'm sure the airline industry doesn't need more problems to tackle in this economy.

And as with any large eruption with a lot of aerosols, everyone likes to talk pretty sunsets ... so keep your eyes open for vivid displays.

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Erik: That almost perfectly circular zone of clear sky centred on the eruption column is something I've never seen before on satellite images. Difficult to believe it's entirely coincidence

Mike Don - I was wondering about that feature myself as I don't remember seeing anything like that before either. I'm no meteorologist, but it might be caused by the proximity of the volcano to the edge of the cloud bank (thus thinner cloud cover) and the ash plume itself punching through the clouds. Any other ideas, folks?

What an amazing image!

I am not inclined to believe that the "hole" in the clouds is coincidental. I would suggest that the clouds in question, stratus clouds (which are low-altitude) according to the EO, have been affected by the shock wave of the initial blast. The pressure wave accompanying the initial eruption of a volcano acts as any other pressure wave associated with an explosion...the clouds were thus displaced in a very neat circle (way too perfect to be a coincidence). The NASA EO description of the image also draws this conclusion. As this image was taken on the 12th of June, it may very well be documenting the first massive burst of pressure from the volcano, hence the violent affect on the clouds in the vicinity.

In any case, I agree Erik, this image is spectacular; possibly the coolest photograph of a volcano I have ever seen.

The only other time I can remember seeing something simialr are on videos of nuclear bomb tests being conducted. I would have to agree with what Chris said, that the shockwave from the eruption caused this.

Simply awesome.

I think you guys are misreading our caption:

"The vigorously rising plume gives the steam a bubble-like appearance; the surrounding atmosphere has been shoved up by the shock wave of the eruption."

I'm pretty sure that's referring to the atmosphere in and above the plume itself, not surrounding the island. The arc of clear air around the island is simply due to the prevailing winds. On the lee side of the island the air is relatively moisture free, so it's clear. For an example see these Von Karman vortices in the Aleutians:

Remember how you could see a faint trace of the shock wave from the Kasatochi eruption moving out in the time lapse? That blew my socks off at the time because I had never seen anything comparable to it before (disregarding A-bombs for the moment).

R. Simmons comment notwithstanding, I side with Chris on this. I have never seen clouds bank up like that UPwind of an island before, though islands can create some pretty interesting patterns. Amazing pic and all credit to you guys at NASA for bringing us this stuff!


I'm no longer a meteorologist, but I used to be one (at Oregon State - small world). I think that the clearing around the volcano is caused by compensatory dpwnward air motion around the vigorous updraft of the eruption column. I used to see similar examples on satellite imagery of thunderstorms and have observed smaller-scale examples in my own skies. We could rule on Von Karman vortices if we had either a wider view version of the image or local wind observations.

The cloud above the eruption column is a pileus (cap) cloud formed when the air above the column was pushed sufficiently high for its water vapor to cool and condense. Pileus clouds are not uncommon above rapidly growing cumulus clouds.

Terrific image!

I've saved this to my screensaver - I find the word "awsome" grossly overused but not here - a superb shot.

The white cloud on top of the column is called (by meteorologists) a pileus (from the Greek for helmet, I think, although Wiki says it's Latin for cap). It is also seen in rapidly developing thunderstorms and is caused by a fast rising column of warm air pushing through a cool level of moisture.
This mirrors the conditions that would be seen here. Footage of nuclear blasts often show the same effect from the shock wave.

By Anne Cotton (not verified) on 18 Jun 2009 #permalink

Al is correct that there is compensatory downdrafting around plumes of rising air. Most of you have probably noticed that it is usually clear immediately following a thunderstorm (even in an ordinary thunderstorm where there is no frontal boundary). In this case, however, I think the shock wave might have more do do with it, given how brilliantly circular the clear feature is.

As pressure increases, so does temperature. The humidity doesn't immediately change where the air is not directly affected by the plume. As the temperature briefly increases, the air is no longer at the dewpoint and the cloud clears almost instantly with the shockwave. Where the plume hits, cloud forms from condensation, as warm moist air, including heat and moisture from the volcano itself, causes the air to reach the dewpoint.

The plume actually increases the depth of the troposphere, and there can be some downward air movement near the top of the troposphere away from the plume, but I don't think this is what is happening in this case, if the plume is only 8km high. The troposphere is usually well over 10km in height in the summertime. I also think that the clear area has nothing to do with Von Karman vortices. The clouds look too high (hard to determine in this case by form), the shape isn't right, I see little if any rotation, and the clearing is more or less centred on the volcano's vent, if you look at where the shade is located.

Why has this decent-sized eruption with substantial sulphur release at stratospheric levels received so little attention in the media? It seems that all they care about is whether air travel is affected. We need to learn to philosphize more often about how fascinating a world and universe we live in.

I just reviewed some photos of atomic blasts and volcanoes, and took a look at the clouds. I now am more convinced that Al is right: that it is a simple downdrafting effect. The shockwave effect should be very short-lived, and I can't see the moisture disappearing. It could be very circular because of the downdrafting and inward-moving air toward the rising air in the long column above the vent becomes more or less circular when you get farther from the centre. So, the whole area directly affected by the blast and close enough for the downdrafting to dissipate the cloud is more or less circular at that distance. Thoughts? Experts on the theme?

Here is some evidence in favour of Al's hypothesis: if you look at images of atomic blasts, there is additional cloud in perfect circles above the plume [does anyone know how this is induced? perhaps the cloud layer is forced ever so slightly upward even though it is a wave and the wave is so short-lived that the pressure effect is also short-lived], but an absence of cloud (sometimes surrounded by a bit of a ring) at lower elevations adjacent to the thin part of the mature plume. The rings appear like they may be swirling, and this behaviour seems a lot more like air adjacent to downdrafting than air affected by a shockwave, which wouldn't last long. I think it is caused by downdrafting. I'll wait a day or so before forming a more solid opinion and wait for others' thoughts.

Got it! As soon as the plume hits a stable layer of air above the clouds, the plume pushes into the stable air. This action forces an opposite reaction, but the continuous energy supply from below forces this opposite reaction to occur in a ring around the plume. Air transported downward from a zone of stability (there is less temperature decrease with elevation in stable air and it warms with increasing pressure as it falls) could result in a sensible heat flux from above instead of below in a localized area around the plume. This causes clear skies around the plume. The pileus cloud above the plume is rather restricted in area and only occurs where the tremendous heat and humidity from the volcano is present, because the plume happens to be rising into a stable layer of the atmosphere (and is destabilizing it in a hurry).

This is O/T but as of this morning at 07-29 GMT, there were NO earthquakes recorded at the Seismic Monitor

This is the first time I personally have seen this, but other specialists will have much more experience. However, could such an apparent cessation of activity herald something larger on its way?

This photograph is only one in a series of about 30 shot by the ISS astronauts of the Sarychev eruption. To see them all, you have to go to the search page of "The Gateway to Astronaut Photography of Earth"

then choose the mission, which is at the very top of the pull-down menu (ISS020 05/20/2009 to present), then choose "Roll E" and in the "frames" windows, give the values "9022" in the upper window and "9052" in the lower one. This gives you the whole sequence of photographs taken from the ISS on 12 June ...


Boris, those photos were useful wrt the above discussion. It shows some evidence of both the downdrafting and the Von Karman effects acting at the same time. You can tell there is downdrafting affecting the cloud, because the clear area to the left of the eruption increases over time in this early stage. However, there is clearly some wind moving (in your images) from left to right, and there are visible rainshadowing effects and the beginnings of a Von Karman vortex (notice the curve in the cloud). So the plume acts a bit like a taller island, except that it is also in motion, so it superimposes downdrafting effects upon the normal aerodynamic motion around an obstruction. Man, an atmospheric physicist could have a field day with this type of phenomenon.

About Sarychev Peak
Is there anyone who can tell me if this eruption is any different from others from the same volcano? In both scale and type. I know there has been small eruptions in the recent past.But before that I do not know. Also is the elemental composition of this volcano known?

By Stephen Cheslin (not verified) on 20 Jun 2009 #permalink

Since Sarychev Peak is in Russian territory english history on this is limited. The warning is the only thing I find in english. It does say the last eruption was in 1976 though.

I will keep searching for more. Hopefully in English.

By theroachman (not verified) on 20 Jun 2009 #permalink


SVERT are also now saying that there are signs of activity at Kharimkotan volcano as well with a possible steam/gas plume from the Severgin cone, which collapsed after an eruption in 1933.

By Bob Skinley (not verified) on 22 Jun 2009 #permalink

I too was intrigued by the circular "hole" in the stratus cloud deck around the volcano. My guess was the same as A. Frank's: that it's caused by a downdraft which compensates for the updrafting air over the volcano. What goes up must have come down.

Re R. Simmon's theory about the arc simply indicating the clear sky on the lee side of the island: if you look at the wider--angle shots in the full NASA download site mentioned by B. Behncke, you'll see that the clear arc is on the *windward* side of the island. You can see a clear area full of diffuse ash on the other side of the island (upper left in the image above): *that's* the lee.

In my experience growing up in Hawaii, a windward stratus cloud deck always extends clear up to the mountaintops. In order to form this "hole" in the clouds, there must be an unusual eruption-induced downdraft, as A. Frank suggested.

By Jason Goodman (not verified) on 22 Jun 2009 #permalink

Regarding the "hole": such cloud-partings are relatively common I think. I've seen many in satellite images of both the Kuril and Aleutian Islands. Typically I can't find a good one to hand right now, but did see one around the island of Ketoy (also in the Kuril Islands):

How far has the sulphur dioxide of Sarychev spread and is it in very small quantities globally now? Thanks

Hannah - I haven't seen updated projections of how long it will take for the Sarychev Peak sulfur dioxide to spread, but my guess is that it is pretty close to be worldwide - albeit in very low concentrations. The bright sunsets across the US are pretty good evidence that the aerosols have at least made it across North America.

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