Monday, February 06, 2006

Ice Cores and the Age of the Earth

Abstract
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.

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 O 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.

The confidence in the chronology becomes less the lower in the ice sheet one goes, however. The amplitude of the annual oscillations slowly decreases relative to other factors, and historic markers are fewer and farther apart. Glaciologists estimate that uncertainties in identification of layers will probably limit the number of countable layers to less than about 8,500 (Hammer, et al., 1978).

Antarctic Ice Cores

The claims that layers of ice were formed 160,000 years ago or more come primarily from interpretation of ice cores in Antarctica (Jouzel, et al., 1987; Barnola, et al., l987). The Soviet Antarctic Expeditions at Vostok in East Antarctica recovered an ice core which was almost 7,000 feet long in a region where the total ice thickness is about 12,000 feet (Lorius, et al., 1979; Lorius, et al., 1985). Since the current precipitation rate is so much less than Greenland (on the order of one inch per year) the crude calculation of age, without corrections for compression and horizontal motion for the lowest layers is more than 100,000 years.

However, such estimates are critically based on the assumption that the accumulation rate has not varied greatly over the past. Unlike the Greenland ice cores, annual oscillations of ð18O and other parameters cannot be traced deeply into the ice sheet on Antarctica. In Greenland, the high precipitation rates not only provide relatively thick annual layers for analysis, but the accumulating snow quickly seals off the ice beneath and protects the record from metamorphosis by pressure and temperature changes in the atmosphere. In Antarctica, by the time the ice has been buried deeply enough to no longer be influenced by the atmosphere, annual variations have been greatly dampened by diffusion (Epstein, et al., 1965; Johnsen, et al., 1972).

The technique used to estimate the age of an ice layer deep in the ice sheet is to measure its ð18O content and compute the atmospheric temperature which is observed to produce such concentrations today (Jouzel and Merlivat, 1984). Through a second-known relation between temperature and precipitation rate, again observed in today's atmosphere, the accumulation rate for a given layer is calculated (Lorius, et al., 1985). Once the accumulation rate is calculated for each layer, the depth and age for each layer in the ice is calculated by integrating the annual accumulation downward from the surface.

There are several historical markers in Antarctica which can be used to cross check these calculations for the past few thousand years. But historical volcanic events are not known beyond a few thousand years in the past which provide any certainty to the calculation of age. This method would be reasonably reliable if precipitation rates had been similar in the past. However, some creationist models predict significant quantities of snow immediately after the Flood (Oard, 1990). Perhaps as much as 95% of the ice near the poles could have accumulated in the first 500 years or so after the Flood.

The Age of the Earth

From a creationist perspective, it would be extremely valuable to thoroughly explore these ice-core data. We would not assume that the precipitation rate has always been similar to that of today. We would expect considerably higher precipitation rates immediately following the Flood. The layers of ice near the bottom of the core should be thicker than expected by the uniformitarian model and contain unusual excursions in ð18O, acidity, and particulates from levels higher in the core. The "annual" layers deep in the Greenland ice sheet may be related to individual storms rather than seasonal accumulations. If these evidences are found, direct information on conditions following the Flood would be available to us.

Nothing in the ice-core data from either Greenland or Antarctica requires the earth to be of great age. In fact, there are good reasons to believe that the ice cores are revealing important information about conditions following the Flood of Genesis and the recent formation of thick ice sheets. Reports of ice-core data containing records of climatic changes as far back as 160,000 years in the past are dependent upon interpretations of these data which could be seriously wrong, if the Genesis Flood occurred as described in the Bible. Further research on ice-core data should be a high priority for creationist researchers.

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Friday, January 27, 2006

How old is the Earth ?

Rocks up to 2800 million years old are common in the great precambrian shield areas, but rocks dating back 3500 million years or more have been found only in a few places. The morton Gneiss from Minnesota, USA, ultrabasic rocks from the Barberton mountain land of swaziland, the warrawoona group from western Australia, and gneisses from west greenland and the antarctic are all examples of these very ancient rocks. The oldest rock in the world is currently a pebble of volcanic ash from a conglomerate near isua, west Greenland, which has yielded U/Pb dates of 3824 +_ 12. other rock close to this age in the same area are the amitsoq gneiss and a banded iron formation. an ancient antarctic rock is also shown in the photograph. these rocks prove that the earth has a solid crust at least 3850 million years ago.

Meteorites have been dated by U/Pb and Rb/Sr methods to about 4600 million years. they are thought to originate in the belt between the orbits of mars and jupiter and to be the fragments of asteroidal bodies which disintegrated long ago. since the uniform orbits of the planets suggest that the solar system had a single origin, it is likely that the Earth, as well as these asteroidal bodies, formed 4600 million years ago. the oldest rocks so far recovered from the moon are coarsely crystalline, quite different from the less ancient basalt lavas and breccias. they seem to be part of the original crust of the moon and have been dated at 4600 million years. as there is every reason to believe that Earth and Moon formed together,this is further indirect evidence for age of the earth. direct evidence comes from the change in lead isotope ratios through time. lead isotopes 206 and 207 are steadily produced by the decay of uranium, and the ratio of their abundance to lead-204 is increasing. formation of lead ore bodies at different times in the past removed lead from the uranium and 'froze' its isotopic composition. their lead isotope radios can be plotted against time on a graph, if this graph is extrapolated back in time, the average isotopic composition of lead in iron meteorites is reached at 4600 million years, suggesting once again that the earth and the asteroidal bodies had a common origin that the date.

The evidence and much more indicates taht by about 4600 million years ago a vast disc-like cloud of gas and dust had condensed to from the star/planet system we know as the solar system, and the earth it self was formed.

Looking further back in time, some estimate can be made of the age of our galaxy with its hundred thousand million stars. most stars seem to have a life cycle of steady size and brightness followed by rapidly in creasing size and decreasing brightness and a final 'white dwarf' stage. calculations involving the luminosity and mass of the oldest stars visible from the earth show them to be about 11 thousand million years old, which is probably the minimum age of the galaxy.

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Friday, January 20, 2006

How old is old ?




A sense of time distinguishes Man form all other animals. Prehistoric and primitive man show by their burial customs a concern for the future and a respect for the past, and modern civilised man put a great deal of effort into trying to reconstruct and understand by gone days.
The methods of the historian and archaeologist are familiar, so that, whether a reconstruction of Victorian Britain or of Neolithic Egypt is presented, it is not difficult for laymen to follow the lines of evidence. But the methods of the geologist working out the history of the Earth are a mystery to many people, and so they are not wholly convinced by his reconstuction.Geological events are so far back in time that the question is constantly asked : how can he be sure ? This writing attempts to explain both the methods and the result of this geological detective work. it will show how the geological time scale has been built up and how the age of the Earth it self is being explored.
Hundreds and even thousands of years are periods of time readily understood by most people. Geologists use a million years as a unit when dealing with Earth history, and talk casually of 50 or 500 million years, time periods quite out side our comprehension. if one hundred years is equivalent to 40 metres, then the 5000 years of recorded history would extend 2 kilometres twenty minutes walk. Most archaeologists work within a 10.000 year time scale that extends 4 km, though a few are concerned with materials ten times this age. The million years back to the start of the ice age in Britain, a recent geological event, take us 400 km, more than the distance from london to paris. to reach the age dinosaurs, 100 million years ago, we would have to walk right around of the Earth ; to represent the whole span of geological time in these terms we would have to do the same thing 46 times.
The three photographs ( figs 1, 2, 3 ) link these different time scales. The Palaeolithic handaxe from the pleistocene of suffolk, 200.000 years old, comes from the base of the archaeologists scale, the top of the geologists. The fact that it was discovered in the year of the French Revolution adds a historical dimension. The necklace was made by Bronze Age man 4000 years ago from fossil sponges that are themselves 80 million years old. in the cave painting a Palaeolithic artist has captured the likeness of an extinct species, otherwise known only from fossil bones, teeth and tusks in Europe.

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