On 12 June 2009, the International Space Station happened to be passing the northern part of the Kuril Islands, a Russian archipelago in the north-west Pacific, just as the Sarychev Peak was erupting explosively for the sixth time since 1946.
This photo was immediately taken by an enthusiastic astronaut, which excited vulcanologists not just because of the early stage of Sarychev’s eruption, but because of several interesting features that can be observed at once in the same image. The characteristic plume that’s rising from the caldera is mainly composed of ash that has been able to ‘mushroom’ naturally on the relatively calm day. Curiously, this has been capped with a white head of steam called a pileus cloud, a result of air rising quickly in a strong updraft and cooling into condensation.
On the ground, there are several columns of molten material winding their way down from the peak which are known as pyroclastic flows; these are superheated currents of rock and gas made fluid by water vapour. The flows are extremely hot (read: up to 1,000 degrees Celsius/1,832 degrees Fahrenheit) and travel very fast, at around 200 metres (656 feet) per second. Their speed, deadly temperature and unpredictability make them especially dangerous in more populated areas.
What scientists can’t quite figure out is the round hole in the cloud above the volcano. To the untrained eye, it would appear that the plume is having an effect on the cloud mass above it. That is a possibility, as the shockwave from the eruption could have punched a hole in the cloud deck or evaporated it as the hot ash rose. But it could easily have been pure coincidence. Sheets of cloud form in these regions where the ocean surface is cool and move with the wind. But when they come into contact with an island, they’re forced upwards into a dry layer of air, which causes them to break up.