Wegener also noted that the continents move up and down to maintain equilibrium in a process called isostasy. As an example he cited the sinking of Northern Hemisphere lands under the weight of continental ice sheets in the last ice age, and their rise since the ice melted some 10,000 years ago.
Drill that is fitted with a Pipe provides effective connection to the rig surface equipment or application with the bit and the bottom hole assembly for the purpose of pumping the Drill fluid to the bit.
A drill chuck is the part of the drill that holds the rotating bit in place. A drill chuck key is a small, ridged tool that fits into the grooves of the chuck to tighten and loosen the chuck. A chuckless drill is one that operates without these two features.