Lava Show in Katla UNESCO Global Geopark

First, the lava from the 1918 eruption of Katla Volcano is heated up to about 1150°C inside a crucible.

The lava is then poured into a showroom where a presenter talks about the lava and audience get to experience the heat, smell and sound of the lava.

As the lava flows into the showroom, it starts to cool down rapidly

Due to the rapid cooling rate, basaltic glass (tachylite) forms:

After each show, the lava is re-used, and each portion of lava can be re-used about a 12-18 times. During each re-melt, portion of the denser chemicals accumulate at the bottom of the crucible and stay there. This leads to the melt getting increasingly more silicic, and eventually, the viscosity of the lava becomes so high that it will not flow properly anymore. By then the lava has stopped being basaltic and is closer to felsic lava. This results in the volcanic glass that forms being obsidian rather than tachylite. The rock here is therefore a man made obsidian. On this video, you can clearly see how high the viscosity of the lava has become.