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　　早期地球大气和海洋

　　内容回顾：

　　Ice layers can provide information of the past climate, top layers are recently produced and bottom of the layers are formed for many years.

　　Air bubbles in the ice can yield climate information as well. By investing the gases in the bubbles, the correlation and conection of carbon dioxide and temperature are revealed.

　　Some sea sediments can also tell information of the climate.

　　参考练习：

　　TPO 10：Variations In The Climate

　　TPO 15：Glacier Formation

　　TPO 19：Discovering the Ice Ages

　　知识拓展：

　　more from：

　　Ice Cores and the Age of the Earth

　　by Larry Vardiman, Ph.D.

　　Evidence for Creation Evidence from Science Evidence from the Earth Sciences Many Earth Clocks Indicate Recent Creation Ice Cores Fit with Recent Creation

　　Introduction

　　It is not uncommon to read that ice cores from the polar regions contain records of climatic change from the distant past. Research teams from the United States, the Soviet Union, Denmark, and France have bored holes over a mile deep into the ice near the poles and removed samples for analysis in their laboratories.

　　Based on flow models, the variation of oxygen isotopes, the concentration of carbon dioxide in trapped air bubbles, the presence of oxygen isotopes, acid concentrations, and particulates, they believe the lowest layers of the ice sheets were laid down over 160,000 years ago. Annual oscillations of such quantities are often evident in the record.

　　Are these records in the ice legitimate? Do they cause a problem for the recent-creation model of earth history? What are we to make of these data? This article will show that the great ages reported for the bottom layers of ice sheets depend on assumed models of past climate and are not the result of direct counting of layers. An alternative model of recent glacier formation following the Flood described in Genesis will be suggested.

　　World War II Airplanes Under the Ice

　　The Greenland Society of Atlanta has recently attempted to excavate a 10-foot diameter shaft in the Greenland ice pack to remove two B-17 Flying Fortresses and six P-38 Lightning fighters trapped under an estimated 250 feet of ice for almost 50 years (Bloomberg, 1989). Aside from the fascination with salvaging several vintage aircraft for parts and movie rights, the fact that these aircraft were buried so deeply in such a short time focuses attention on the time scales used to estimate the chronologies of ice.

　　If the aircraft were buried under about 250 feet of ice and snow in about 50 years, this means the ice sheet has been accumulating at an average rate of five feet per year. The Greenland ice sheet averages almost 4000 feet thick. If we were to assume the ice sheet has been accumulating at this rate since its beginning, it would take less than 1000 years for it to form and the recent-creation model might seem to be vindicated.

　　Greenland Ice Cores

　　However, life is never as simple as implied above. In making our calculations, we did not take into account the compaction of the snow into ice as it is weighted down by the snow above. Neither did we consider the thinning of ice layers as the tremendous weight above forces the ice at lower levels to squeeze out horizontally. More importantly, we did not consider the average precipitation rate and actual depths of ice for different locations on the Greenland ice sheet.

　　When these factors are taken into account, the average annual thickness of ice at Camp Century located near the northern tip of Greenland is believed to vary from about fourteen inches near the surface to less than two inches near the bottom (Hammer, et al., 1978). If, for simplicity, we assume the average annual thickness to be the mean between the annual thickness at the top and at the bottom (about eight inches), this still gives an age of less than 6000 years for the 4000-foot-thick ice sheet to form under uniformitarian conditions.

　　This is in relatively good agreement with the number of annual oscillations of 18O currently observed in Greenland cores. Although occasional ambiguities occur, it is relatively easy to count annual layers downward from the surface through considerable depths in the Greenland ice sheet. This is possible because of the large precipitation rates in Greenland and the preservation of the annual effects.

　　It is also possible with a high degree of accuracy to cross check the counting of annual layers with occasional peaks in acidity and particulates from the fallout of historic volcanic events. Hammer, et al. (1978) have correlated the peaks in the mean acidity of annual layers from 553 to 1972 A.D. with historic volcanic events. About a dozen historical volcanic eruptions are evident in the ice core from Crete in central Greenland. Several unknown eruptions are also documented in the ice core record.