So an example of them is you found a naturally generated lava lake connecting to a ravine, it is not flowing into the ravine, and you decide to mine a iron ore next to the lava and you expect nothing is going to happen, when you mine it, the lava flows and burned you and eventually you fell off the cliff and died. It happens the same with naturally generated water lake or a waterlogged block that is not flowing if you do it with a trick, I also wanted to mention about MC-222654 .