While the Halo franchise has used it a lot, other franchises have also mentioned/threatened with the idea of glassing a planet. The sheer heat of the attacks used on the planet to make it uninhabitable would cause the surface to turn to glass.
Now this likely originates from the Trinity nuclear test where they found glass like structures around the explosion site, which they dubbed Trinitite. It is the silicates in the soil heated up so it is likely not an entire planet would be glass, just the parts with lots of sillicates in the ground.
Now what I would want to know is how a “glassed” planet would truly look like for anyone who comes back and tries to terraform it, it is a planet in the Goldilocks zone after all. I would like to know the average surface consistency, how thick the glass would be in places where it does form and what the atmosphere would be like. Some constraints as to what I expect from the glassed planet:
- it was an Earth-like planet beforehand
- It is glassed by primarily heat based weapons, plasma and lasers* for example
- the colonists return to the world 3 years after the glassing happened (can be altered if it is unsurvivable otherwise)
- the planet needs terraforming, of course the colonists will be wearing protective gear outside
- The temperature of the weapons is 3000 degrees.
- All land surfaces that can hold infrastructure are destroyed, the sea’s aren’t specifically targeted.
*lasers of a frequency that interacts little with the atmosphere.