You Shall Not Pass:

Seismic activity is not common place in Africa because fault lines and tectonic plates are few and far between. My experience of the Earth moving under my has occurred three times while under African blue skies, each time barely stirring me from slumber. Some speculate the extensive mining infrastructure cross crossing the affected zone of the highveld. The endless shafts and tunnels peppering the Witwatersrand may have something to do with it. I have another theory. I considered Graboids but none of the seismoraphers around the cradle of humankind even blipped. What if we unearthed a Balrog?

My theory is the nearly three decades of illegal sub surface mining has compromised the structural integrity of the mknes and now we have tremors. As Gandalf put it they were to greedy and they dug too deep and something deep below was awoken.