Paleo Slide Set: Polar Ice Cores
GISP2 cores span 200,000 years of climate history

On Thursday, July 1, 1993, GISP2 drillers struck rock, completing one of the longest environmental 
records (3053.51 m, over 200,000 yr of the Earth's climate history) ever obtained from an ice core. 
After 5 years of drilling, researchers from 18 United States educational and research institutions 
had finally achieved their goal of boring nearly two miles to the very bottom of the ice sheet. 
The cores in this photo show the sharp change from clear to silty ice that occurs at a depth of 3040.33 m. 
The transition is followed by alternating bands of silty and clear ice followed by progressively siltier 
ice until contact with bedrock at 3053.51 m. Researchers postulate that the silty ice formed when melting 
ice at the base of the sheet incorporated bedrock debris and refroze. 

Photo Credits:
J. S. Putscher 
GISP2 SMO, University of New Hampshire.