Have you ever wanted to step inside a volcano? This summer a tour company is offering the chance of travelling down into the magma chamber/lava tube system/shallow magma storage area of Thrihnukagigur volcano. This volcano was talked about in a post by Erik from eruptions at some point last year. Whilst there is some controvesy over what to call the area beneath the volano, there is no doubt that an opportunity for the general public to explore a feature such as this is brilliant and is something I would love to do myself!
If any one can read Icelandic (which I can't I'm afraid!), there is a website here which gives some info and pictures and diagrams on the volcano and the area. There is some info on the volcano and the area in English here on the tour website. The video below gives a good overview of the size of the volcano and the gap underneath.
I can't comment with any certainty on the matter having not visited myself (its always best to look at things in the flesh and be there, you get a much clearer picture and can make clearer judgements for yourself!), however I am going to put my 2 cents in about the crater itself anyway.
As a cinder cone the type of activity at Thrihnukagigur volcano will be much like some of the episodes at Etna which have created cinder cones there over the years, and as such, present an interesting incite into processes below the surface during such events. The vivid colours inside the volcano demonstrate the high gas content and activity of the magma, further confirming the type of activity there. In certain volcanoes worldwide there are lava lakes and these can be seen to ebb and flow in height and activity, therefore we can accept that other volcanoes in similar situations will do this too and can often be seen as 'tide marks' of sort. It is certainly fortunate for us that the magma drained away (which there could be a few reasons why this happened) as we now have access to something quite beautiful and it does provide scope for research into the shallow plumbing systems of volcanoes.
A while back this tour was featured in a TV program (National Geographic) and yes while some of these shows can be sensationalist (not all of them!) one thing they do very well is promote interest in the science behind them and encourage people to investigate further so they are not necessarily a bad thing. There are a host of video and even the National Geographic program on the website which are worth a watch if you have some spare time!