For the last couple of days, the science blogs have been going nuts over photos, shot from the ISS, of an in-progress volcanic eruption. Back on June 12, Sarychev Peak on Ostrov Matua (Matua Island) in the Kuril Island chain erupted right around the time the ISS was passing over. You can download hi-resolution versions of the pictures from the Gateway of Astronaut Photography.

Video Animation:

The pictures are quite stunning as they reveal a number of interesting eruption features, not normally seen from above.

Sarychev Eruption

For example, I counted at least 3 pyroclastic flows coming down the flanks of the volcano; you can see the steam erupting from where two of them enter the sea at the 1 o’clock and 9 o’clock positions on the island. Note the bubble of condensation at the top of the mushroom cloud. Scientists are not sure if that’s caused by moisture erupting from the volcano itself (that’s why the ash cloud is whitish), or from atmospheric moisture shoved up into the stratosphere. Also, there seems to be some dispute over the cause of the round “hole” in the clouds surrounding the island:

One explanation is that the hole in the clouds has nothing to do with the eruption at all. In places where islands are surrounded by oceans with cool surface temperatures, it is common for a sheet of clouds to form and drift with the low-level winds. When the cloud layer encounters an island, the moist air closer to the surface is forced upward. Because the air above the marine layer is dry, the clouds evaporate, leaving a hole in the cloud deck. These openings, or wakes, in the clouds can extend far downwind of the island, sometimes wrapping into swirling eddies called von Karman vortices.

The other two possibilities that scientists have offered appeared in the original caption. One is that the shockwave from the eruption shoved up the overlying atmosphere and disturbed the cloud deck, either making a hole or widening an existing opening. The final possibility is that as the plume rises, air flows down around the sides like water flowing off the back of a surfacing dolphin. As air sinks, it tends to warm and expand; clouds in the air evaporate.

The NASA Earth Observatory site has some interesting pictures taken from their satellites showing the ash cloud as it dispersed over several days. What is more interesting to me are the beautiful von Karmann vortices surrounding the islands.

Kuril Islands

I broke out the Shake and made an animation of the eruption. It’s not quite the morph the NASA guys did, but I thought I’d teach myself something about image stabilization. Enjoy:

Sarachev eruption: Image Science & Analysis Laboratory, NASA Johnson Space Center
MODIS satellite of Kuril Islands: NASA