<P> Impurities in the ice provide information on the environment from when they were deposited . These include soot , ash , and other types of particle from forest fires and volcanoes ; isotopes such as beryllium - 10 created by cosmic rays ; micrometeorites ; and pollen . The lowest layer of a glacier , called basal ice , is frequently formed of subglacial meltwater that has refrozen . It can be up to about 20 m thick , and though it has scientific value ( for example , it may contain subglacial microbial populations ) , it often does not retain stratigraphic information . </P>
<P> Impurities in the ice provide information on the environment from when they were deposited . These include soot , ash , and other types of particle from forest fires and volcanoes ; isotopes such as beryllium - 10 created by cosmic rays ; micrometeorites ; and pollen . The lowest layer of a glacier , called basal ice , is frequently formed of subglacial meltwater that has refrozen . It can be up to about 20 m thick , and though it has scientific value ( for example , it may contain subglacial microbial populations ) , it often does not retain stratigraphic information . </P>
what part of the ice core is actually examined by scientists
what part of the ice core is actually examined by scientists
Impurities in the ice
Impurities in the ice