Less than two years later, as the graph indicates, scientists detected Chernobyl radioactivity in snow at the South Pole--a graphic reminder of how small our planet is. Distinct annual layers stand out because, in snow that falls in summer, crystals are larger and acidity higher than in winter snow. (This represents about 11,350 feet of ice accumulation.) The graph clearly shows how a rise in gases will mean a rise in global temperature (though whether rising gases trigger rising temperatures, or vice versa, remains unknown).
Nature's Time Machine How would you like to have a time machine that could take you back anywhere over the past 300,000 years? Scientists collect ice cores by driving a hollow tube deep into the miles-thick ice sheets of Antarctica and Greenland (and in glaciers elsewhere). Detected on this graph, which displays volcanic sulfate levels between 20,000 and 110,000 years ago, Toba was the largest eruption of the past 500,000 years. Here we model this event and its atmospheric effects and compare it to extensive ice core data.Panels A through D correspond to Dome Fuji (Antarctica), WDC (Antarctica), NGRIP (Greenland) and NEEM (Greenland), respectively. ANSWER: Relative dating is used to determine the relative ages of geologic strata, artifacts, historical events, etc.This technique does not give specific ages to items.