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 center 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.