When we think of craters, asteroid collisions are often what come to mind. But now, thanks to scientists who exploded balloons in a sand box, we have a better idea of other ways craters can be formed, like underground methane explosions, for instance.
First, the scientists buried balloons in a sand box, and then “detonated” them using a needle. Upon detonation, a dome bulges out of the ground like some kind of high-pressure geological zit. Then it completely explodes, triggering what New Scientist calls “underground avalanches,” whose momentum propels a skinny, otherworldly tower of sand to thrust into the air in the centre of the site. The depression that’s formed all around it is what becomes a crater.
This simulation can help us figure out the origins of otherwise mysterious craters — perhaps, buried bombs, methane explosions, or maars, volcanic craters left by underground mixing of magma and water that cause explosions. All these craters differ from asteroid craters because the latter leave a “rim”, while these look more like a big sinkhole.