Paleo Slide Set: Polar Ice Cores
GISP2 drill from inside the drilling dome

This is a view of the GISP2 drill from inside the drilling dome. With each coring 
run approximately 5-6 m of ice is recovered. The drill is 20 m long and is lowered 
into the borehole on a 4 km long kevlar cable. Because ice at depth is under tremendous 
pressure and easily deforms, the hole created by the drill would close on itself from 
the pressure of the surrounding ice were nothing in the hole to supply back pressure. 
The GISP2 drillers fill the entire borehole to within 100 m of the surface with butyl 
acetate, an organic compound, to keep the hole from closing on itself. Clearly visible 
in the picture is the innovative carousel system that permits drilling to continue while 
ice core sections are being unloaded. After the drill is hauled to the surface, the 
core-filled barrel is rotated out of the drill assembly, emptied, and replaced with a 
fresh barrel. The drill can then be lowered into the hole for another coring run. 

Photo Credits:
Mark Twickler 
GISP2 SMO, University of New Hampshire.