Anak Krakatau

Anatomy of an Ash Column

In November 2007 a 100m wide vent was highly active on the south side of a 350m high cone located on Anak Krakatau. Here we show details of the phreatomagmatic activity as seen from a boat stationed about 500 metres from the vent.

Anatomy of an Ash Column
Phreatomagmatic eruptions eject a "cocktail" of bombs, lapilli and ash.
Anatomy of an Ash Column
Large bombs sometimes flew in our direction, but never actually reached the sea.
Anatomy of an Ash Column
Some incandescent bombs appear like fiber optics tubes.
Anatomy of an Ash Column
Dust caused by impacting bombs obscure parts of the cone.
Anatomy of an Ash Column
Sometimes hot ash is erupted in such quantities that minor pyroclastic flows are generated.
Anatomy of an Ash Column
Often the bomb's ash trails create intriguing patterns reminiscent of flowers on a velvet fabric.
Anatomy of an Ash Column
After the initial blast, the ash column rises while bombs fall all around the vent.
Anatomy of an Ash Column
As the ash column rises creating vortices, a car-sized incandescent bomb falls on the right.
Anatomy of an Ash Column
In the morning twilight, only few bombs appear incandescent, while others seem black.
Anatomy of an Ash Column
Ejection of huge blocks forming remarkable trails inside the cloud of ash and lapilli.
Anatomy of an Ash Column
On 23rd November larger amounts of fresh magma rise within the conduit, and lava is ejected violently.
Anatomy of an Ash Column
Another explosive blast: Some of the lava's incandescence is absorbed by the dense ash column.
Anatomy of an Ash Column
This is the first photo in series of three showing the development of a typical eruption.
Anatomy of an Ash Column
After two seconds, the biggest bombs start falling, creating turbulent ash trails.
Anatomy of an Ash Column
The biggest bombs have already impacted and roll down the flanks, while smaller ones continue to fall.
Anatomy of an Ash Column
Often the bomb's ash trails are so thick as to create "ash roots" which seem to sustain the rising ash column.
Photos by Marco Fulle, taken during four boat trips from 21 to 24 Nov 2007, sometimes in the early dawn when the bomb's incandescence was visible. All photos were taken with a 135mm lens and a digicam (equivalent focal length of 200mm on 24x36 film).