2.5 Km isn't all that deep for a drill. I've spent more time then I would like to admit on a LF230 Rig and depending on the rod size they can go a lot deeper. I imagine the drilling went something like this: So you are drilling down, maintaining torque and rodfeed, all of a sudden you hit a void (this case magma pocket) and your torque drops off to zero your rodfeed hits zero resistance. So you stop the rods slowly, you don't want a twist off in a void. You turn up your mud, you notice that there is some serious pressure in your rods, you pull the rods up 20 or so feet. By this time your core barrel is filled with magma and melting, but it's in a nice wet mud casing cooling it. You then notice the pressure wont drop cause your drill shoe is solid rock. You turn off the mud, look over at your helper, grin and say it's gonna be a fun night. You then proceed to remove all 2.5km of rods from the whole, a big pain in the ass. The whole trip out is wet as the mud has nowhere to go but out of where you disconnect them every 40 feet or so, the drilling helper and hopefully the drill op is soaked in mud. They finally get to the last 10 ft rod, look down the rod at a giant tube of rock, the helper runs out of the rig, the operator starts throwing stuff. Nothing amazing, a 2 or 3 in diameter tube of cooled magma sits in your rod. You just ruined $50K+ worth of stuff depending on the rods, the bit, the core barrel, and etc. You then proceed to wait for the foreman to come and laugh at you.