Parameter Tree:
EARTH SCIENCE > PALEOCLIMATE > ICE CORE RECORDS

Definition:
An ice core is a section of ice drilled from a glacier or ice sheet. Ice
deposits contain samples of the atmosphere at the time the ice formed; they
also record seasonal fluctuations of temperature and dust. That's why ice cores
are extremely valuable sources of paleoclimate data on the Earth's climate
in the distant past. Researchers drill sections of ice cores hundreds of meters
long and then match sections at different depths with particular eras in the
Earth's past. These sections can then be analyzed for clues about atmospheric
gases and temperatures from hundreds of thousands of years ago.


Reference:
From: The Exploratorium:
http://www.exploratorium.edu/climate/glossary/ice-core.html