I have a theory that these perfectly round sinkholes are perhaps ancient extraction sites where a previous civilization has drilled for resources or what have you, then plugged it up after they were finished. Similar to the way we drill for oil today, get the resource, plug the hole and move on.

They most certainly look like they've been created by a massive drill or perhaps high powered energy beam.

Perhaps the material used to plug these holes is finally giving way, due to age and/or/bot the current earth changes we're experiencing.