Monday, November 08, 2004

Mount St Helens - update

There is little visible change to be seen on the Volcanocam images today. The weather is clear and a gentle plume is rising from the crater. A number of press reports are saying that the lava dome (the presumed source of the nightime glow) has extruded an additional 100m since last week and is developing large piston shaped extrusions 30-35m high.

This constant movement of new lava to the surface is the most likely cause of the nightime glow. Over the last few days the relatively quiet nature of the volcano has made it possible to look more closely at the source of the glow in successive images from the volcanocam.

One observation is that the glow only appears on the Volcanocam images after the light level has decreased to the point where the camera effectively stops responding to colour and the noise levels increase. This may be due to the camera auto switching to b&w mode and increasing the gain, hence the higher noise levels. It is also interesting that the location of the most persistent of the glows from night-to-night, doesn't seem to correspond to the source of the central plume that you can see today in the Volcanocam.

I'm going to try and generate some images to examine this further and post them on the website soon. In the meantime, I have posted a movie of last nights display here.

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