Here's a curious engineering idea - getting volcanoes to build your house for you. Designer Kieren Jones' Volcano Project is a theoretical proposal to make something useful of lava flows, turning them into a construction method. Here he is, talking to Dezeen:
At present the method for mitigating the destruction of lava flows is to place large concrete blocks in the predicted path of the flowing lava and spraying it with sea water in order to try and cool this molten material.
Instead of placing large concrete blocks in its path, I propose to create large casting beds into which the lava can flow, creating building blocks for future shelters. Not only would these casting beds protect the population at the base of the volcanoes but they will also provide them with a constructive material in which to aid the recovery of a community post eruption.
It treats volcanoes as something akin to blast ovens, pumping out a product that we can utilise in just the same way that we might make a concrete or steel structure. Stick those pieces together to form any new building you want, provided you've got the tools to get such large chunks of rock out of the earth intact.
Using volcanic rock as construction materials isn't new, of course. The communities that live beneath volcanoes take full advantage of all that hard, pretty granite and basalt lying around everywhere in large brick-sized chunks, using it to build their homes. What's different here is reversing the process - instead of carving out the shape you want from the rock after it cools, you make the shape first and then dig it out of the ground.
Jones is specifically thinking here that it would be suited to the Decade Volcanoes, which are not (as their name might suggest) volcanoes that tend to erupt every ten years. Instead the description comes from the International Decade for Natural Disaster Reduction (that's the 1990s), when the UN set up a bunch of programmes to investigate ways to reduce the danger from floods, hurricanes and eruptions to people around the world.
The 14 Decade Volcanoes include mountains like Etna in Italy, Santa Maria in Guatemala, and Merapi in Indonesia - volcanoes which have a history of regular, large eruptions, and which are located close to populated areas. Despite the danger they pose to towns and cities nearby, they are also relatively well-studied, making it easier to both predict when an eruption is likely due and which defences will be needed to avert disaster. When Etna erupted in 1992 the lava flow overwhelmed the concrete barriers put in place, threatening the town of Zafferana - scientists blew a hole in the roof of a lava tube and droppped concrete blocks into the underground flow, blocking it up and saving the town.
There's beauty in the thought of turning this destructive force into something creative. However, as the Etna example shows, volcanoes are dangerous, difficult things to try and control. Imagine if you travel to where you dug your hole only to find the lava has covered it several metres thicker than you expected, and you've got to break through all of that before you even get to the tricky bit of trying to lift the bit you want out of the ground.