No one was injured, but these images remain particularly spectacular.
This weekend, in a remote mining area 665 north of Santiago, capital of Chile, the operators of a copper mine had a funny surprise: a huge hole opened up in the middle of the ground. The mechanisms that lead to the appearance of these structures are relatively well known; but in this specific case, specialists are still skeptical about the exact phenomenon that triggered it.
These huge ditches, geologists call them “sinkholes”. They occur in a particular geological environment; we speak of karst by analogy with the Slovenian-Croatian massif which gave it its name. It is also found in France, for example in the Vercors. The karst is characterized by a set of carbonate rocks, mostly limestoneswhich have the particularity of being relatively soluble.
Rainwater, on the other hand, is slightly acidic. She is therefore able to dissolve these rocks when exposed to it over the long term. Over the centuries, runoff that has seeped deep into the rock has attacked the overall structure, causing cracks to open in the subsoil. These then allow the liquid to infiltrate even deeper, and so on. Eventually, the passage of water can end up digging a complex network of underground cavities.
And when this process continues for decades, even centuries, the subsoil begins to look like real Swiss cheese; when it becomes too porous, it collapses under its own weight, leaving behind a pit that can be as spectacular as it is voluminous.
A huge hole originally still blurred
In this specific case, the yawning abyss indeed measures 32 meters in diameter. It’s more than the length of a tennis court. Its depth is also remarkable since it reaches about 200 meters deep. More or less, this means that we could almost fit the Montparnasse tower there or stack four Arcs de Triomphe!
Fortunately, nobody was hurt. Infrastructure and equipment have not suffered either. But for the sake of conscience, all operations of the exploitation have been suspended until further notice. The local authorities are taking the situation very seriously and want to shed full light on the situation before resuming prospecting.
“We would like the cause to be clarified”, explained the local mayor in an interview. “It must be determined whether this collapse is a consequence of the mining activity or something else”, he specifies.
In any case, the bottom of the hole did not particularly inform them; they found nothing but water; anything but surprising in this context. Since this sinkhole is very young, you should not have expected to find a century-old forest there, as was the case at the bottom of another spectacular sinkhole spotted in China last May (see our article).
Scientifically, it is therefore less interesting at first sight; but its study will allow geologists and operators to learn more about the structure of the subsoil in the area. This will allow them to continue their activity while minimizing as much as possible the environmental risks associated with this activity.