Lab - Vostok Ice Core. Vostok Ice Core Map showing Antarctica and location of Vostok Ice Core.
Colors indicate elevation.
These annual layers provide a record of the earth's climate that reaches back as much as 200,000 years. Various kinds of fallout from the atmosphere, including airborne continental dust and biological material, volcanic debris, sea salts, cosmic particles, and isotopes produced by cosmic radiation, are deposited on the ice sheet surface along with the snow, thus mixing with the snow and also acting as a distinctive barrier between different ice layers. The composition of bubbles of air trapped in the ice is a measure of the composition of the atmosphere in ancient times. With increasing pressure from subsequent snow deposition on an ice cap or glacier, the snow becomes compacted and, consequently, air is trapped within the deposited layer. This entrapment of air occurs essentially with no differentiation of the atmospheric gas components.