Atlantis Enigma - Chapter 8
CRACKS IN THE CONSENSUS
COLD IN ITSELF DOES NOT LEAD TO GLACIATION. ONCE YOU REALIZE THIS, IT COMES AS (SLIGHTLY) LESS OF A SURPRISE TO DISCOVER THAT THE FIRST PREREQUISITE OF AN ICE AGE IS A RISE IN TEMPERATURE, NOT A FALL.
When geology emerged as a scientific discipline in the early nineteenth century, its pioneers were faced with widespread evidence that massive changes had affected the Earth in relatively recent times. Something had polished and scratched the surface of many rocks and the world was strewn with debris. There were literally millions of displaced boulders, known because of their location as 'erratics'. They appeared in the most peculiar places: delicately perched on mountain peaks, choking valleys in their thousands, or standing in splendid isolation in a meadow. The question that faced those early geologists was obvious: what had moved the boulders?
The mystery seemed somehow connected with the polished surfaces seen on some rocks and the striations seen on many others, including the erratics themselves. These striations had a common alignment - north-west to south-east - whether the rocks that bore them were found in the northern or southern hemisphere. Typically they appeared on the summits of high hills or on the northern or north-western slopes of mountains.
Clearly, whatever caused the scratches must have originated in the north or north-west and moved in a constant direction across the surface of our planet. It seemed logical to assume the same force that scratched the rocks had carried the erratics with it.
But what was the nature of that force?
Whatever it was did more than carry boulders and scratch rocks. Gravel and sand deposits were found banked up against the northern or north-western slopes of mountains. Muggendorf, in Germany, was typical of many sites at which northward and north-westward facing caves and fissures were packed with these silts. Investigation indicated recent geological origins.
Early solutions to the problem were in keeping with their time. For centuries, the Western world had accepted the biblical story of a universal flood. Even scientists with an openly atheistic bent - rare enough at the beginning of the nineteenth century - were hard put to free themselves of the cultural influence. Almost without exception, early geologists concluded it was water that carried the erratics. They proposed terrifying scenarios of vast rivers overflowing, or gigantic submarine earthquakes creating enormous tidal waves.
In 1802, the first dissenting voice arose, John Playfair, a mathematician, concluded that glaciers were the only natural phenomenon capable of transporting rocks over large distances. He published his theory and was ignored.
Ice continued to hold a certain fascination. In 1821, a Swiss engineer named Ignaz Venetz published evidence of large-scale Alpine glaciation at some point in the past. The geologist Jens Esmarch soon afterwards proposed there had once been a much greater extension of the glaciers still seen in his native Norway. Just eleven years later, Professor A. Bernhardi was claiming that the (North) polar ice cap had formerly extended far south into Germany, thus explaining the extraordinary number of erratics on the German plain.
In 1837, glacial theory emerged again, this time in an even more spectacular form. The Swiss palaeontologist Louis Agassiz delivered a startling address to the Helvetian Society. In it, he proposed that erratics, till and striated rock pavements were all evidence of an Ice Age - a term he borrowed from the botanist and poet Karl Schimper, who had used it in one of his verses.
Agassiz painted a vivid word picture of glacial ice extending from the North Pole to the shores of the Mediterranean. His ideas were not well received. Agassiz was best known for his work on fossil fish. One distinguished scientist, Alexander von Humboldt, advised him to get back to them. He ignored the advice and began intensive field studies. They confirmed his conclusions to such an extent that in 1840 he published his ground-breaking "Études sur les Glaciers" ('Studies of Glaciers') which demonstrated that Alpine glaciers had been far more extensive in the past. That same year he visited the British Isles to extend his glacial doctrine to Scotland, northern England and Ireland. In 1846 he traveled to North America where he found additional evidence for an Ice Age.
It was an idea whose time had come. Just two years later, Karl Ernst Adolf von Hoff, who was competing for a prize put up by the Royal Society of the Sciences in Gottingen, Germany, also denied the 'violent water' theory of erratics. He replaced it with the notion that drift ice might have carried the boulders and soon found his concept had attracted supporters.
Among them was Schimper, from whom Agassiz had borrowed the term Ice Age in the first place. Like von Hoff, Schimper believed the solution to the problem was floating icebergs. He became an enormous nuisance in his attempts to draw attention to his ideas, and eventually died insane.
A controversy erupted between the floating iceberg theorists who, essentially, were proposing a modification of the old Universal Flood hypothesis - and those few scientists who were attracted to Agassiz's Ice Age glaciers concept. It was settled by the intervention of the British geologist Charles Lyell.
Lyell was one of the most distinguished scientists of his day. His reputation was based on a massive interpretation of geological history entitled Principles of Geology, the first volume of which had been published in 1830. In this work, Lyell took issue with virtually every geologist on the planet. Whether by flood, floating ice or divine intervention, there was a clear consensus that what happened to the world had been abrupt, sudden, catastrophic. Lyell maintained it was nothing of the sort.
As Lyell saw it, the causes of geologic change have always been gradual and constant. What is happening today - essentially slow weathering through wind and rain, slow earth movements, slow mountain building - is what has always happened in the past. There might be a few localized aberrations caused by volcanic action, earthquake or flood, but taking things as a whole, there had never been sudden, violent changes.
Although Agassiz himself believed the onset of his Ice Age had been sudden, Lyell did not. In the slow creep of glaciers he saw a reflection of his own uniformitarian ideas. When Lyell threw his massive prestige behind the theory of an Ice Age, Agassiz shut up about catastrophic beginnings. It proved to be a useful tradeoff. With Lyell on his side, Agassiz quickly found his ideas were now being treated with profound respect.
Those ideas had become quite spectacular, having progressed far beyond his original observations about Alpine glaciers. He believed that temperatures had plunged repeatedly before the Alpine glaciation and a sea of ice had covered almost all of northern and western Europe, extending down across the western reaches of the Mediterranean into North Africa as far as the Atlas mountains. There were similar immense ice sheets covering north-west Asia and much of North America. Only the topmost peaks of mountain ranges emerged from these vast seas, as solitary islands.
Now he could no longer advocate a catastrophic beginning to his Ice Age, Agassiz made no proposals at all about what had caused the temperatures to plummet in the first place. He simply said the climate changed - which explained nothing.
Once the basic idea started to be taken seriously, scientists began to spot its weaknesses. One of the most glaring was that ice sheets can't move of their own accord. In order to blanket the vast areas of Agassiz's speculations, they had to move down from higher ground.
A new theory arose. This called for the eruption of an extensive range of very high mountains at or near the North Pole. The rise of these mountains pushed accumulated ice downwards and outwards to form the new ice sheets. The Ice Age ended when, for reasons of their own, the Polar mountains disappeared. Agassiz's sea of ice, no longer replenished by fresh supplies from the Arctic, simply melted. Although no one at that time (or since) had discovered the slightest trace of the Polar mountains, their existence was so widely assumed by the scientific community that they came to be taken as an established fact. As was the reality of Agassiz's Ice Age.
The ready acceptance of disappearing mountains was made possible by the fact that Agassiz and others believed their Ice Age to have been a one-off event - something triggered by freak conditions that lasted a limited time, then returned to a warmer normality.
But then a Scots geologist, Andrew Ramsay, announced evidence of not one Ice Age, but two. In Switzerland, botanist Oswald Heer confirmed his findings by discovering deposits which contained the remains of warm-weather plants and animals. He concluded there had to be an 'Inter-glacial' period during which they had flourished.
These discoveries proved to be the start of a movement as inexorable as the creep of ice.
Successive geologists increased the number of ice ages from Ramsay's two to three or four, then five or six, then seven or more, all with warm inter-glacial periods of greater or lesser duration. Agassiz's relatively moderate proposal had been extended to encompass a 2.5-million-year-long Ice Age punctuated by brief periods of warm or temperate weather.
In the excitement generated by this awesome concept, nobody stopped to wonder why the Polar mountains kept popping up and down like yo-yos.
Although there have been modifications to Agassiz's original vision of vast seas of ice, science today still firmly believes in a Pleistocene Ice Age. Indeed, fresh discoveries have extended the theory beyond anything the Victorian geologists envisaged. 'Ice scour' on Precambrian rock strata has suggested a primeval Ice Age in eastern Asia and the south Pacific. India, Australia, South Africa and South America all seem to have experienced an Ice Age in the Permian. There is localized evidence of glacial spread in the Silurian and Cretaceous.
The multiplicity of Ice Ages has made the question of cause all the more urgent, but it is a question that has yet to be answered. There have, of course, been theories.
Astronomers postulate that every 220 to 250 million years the solar system enters one of two space clouds - areas characterized by billions of tiny particles of floating matter. With these particles absorbing solar radiation, it may be that the planet would cool down enough to start an Ice Age.
Another theory holds that a massive increase in sunspots might reduce solar radiation, even if we weren't In a space cloud at the time.
The Yugoslav astronomer, Milutin Milankovich, once took time to compare eccentricities in the Earth's orbit with peculiarities in the inclination of the planetary axis. He found nine points in the last 600,000 years during which he believed the Earth was likely to endure extreme cold. His findings created a stir since they agreed rather well with currently proposed dating of glacier advances during the Pleistocene. The excitement died down when an extension of his calculations failed to show any correlation with earlier Ice Ages.
D. S. Allan and J. B. Delair list eight categories of theory explaining the advent of an Ice Age.(22) These categories are:
1 Astronomical influence. Theories in this category vary from meteor bombardment to the solar system's movement into an unusually chill area of space.
2 Atmospheric change. Some of the ideas put forward under this heading are of particular relevance to our present age. They include diminished atmospheric carbon dioxide - a sort of reverse greenhouse effect - and/or changes in the ozone layer. Increases in atmospheric dust content (as a result of volcanic activity, for example) would also tend to cut back the amount of heat from the sun reaching our planet.
3 Axial/Orbital change. A tilt in the Earth's axis would move certain areas of the planet away from the sun. A lengthening of the orbit would move the whole planet. Both obviously lead to temperature drops.
4 Geophysical change. The theory of continental drift, now widely accepted by the scientific community, might just possibly be extended to encompass the idea of land masses drifting into the polar regions, collecting a covering of ice, then drifting out again . Some scientists believe the known movement of the poles - which reflects gradual changes in the Earth's axis of rotation - might in certain circumstances lead to planetary chilling.
5 Glaciological change. Here the theorists postulate periodic melting of the underlying layers in the planet's natural ice caps. This would lead to a surge outwards of the upper layers with consequent influence on sea levels.
6 Land/Water change. Some theories in this category are variations on the old Polar mountains idea since they suggest the upward movement of massive land areas. Once they breach the snowline, a vast reservoir of ice would naturally form with glaciers sliding down to cover lower-lying districts. Water theories include changes in ocean currents or general circulation or even wholesale relocation of the oceans themselves.
7 Meteorological change. Here we are back to Agassiz's bland assertion of a change in climate, without any real attempt to explain why. But in fairness to modern proponents of the theory, a fall in global temperature is now generally thought of as a mechanism for maintaining the ice once it was formed rather than triggering its formation in the first place.
8 Solar emission change. This category encompasses the various theories that suggest solar radiation has changed in intensity and/or composition from time to time, thus reducing the amount of heat received by Earth.
It is probably fair to say that while many of the theories show considerable ingenuity, none of them is generally accepted as an adequate explanation of the Ice Age. But their failure is hardly surprising since they are all based on a wrong assumption. This is the assumption that what triggers an Ice Age is cold.
Today, the coldest region on the face of the planet is Siberia. It is colder than Greenland, colder than Antarctica. Yet while Greenland and Antarctica are covered by ice sheets, Siberia is not.
Cold in itself does not lead to glaciation. Once you realize this, it comes as (slightly) less of a surprise to discover that the first prerequisite of an Ice Age is a rise in temperature, not a fall.
For ice to form, you need water. In nature, this water is supplied by rainfall. Rain, in turn, arises out of evaporation from the oceans.
To produce the volume of ice believed to cover the Earth during the Pleistocene Ice Age, ocean levels are calculated to have dropped by as much as 1,000 feet in places . But this drop must have occurred before the formation of the ice, not after - something that requires a dramatic rise in world temperature. Although the temperature rise could be gradual, it would have to be followed by a sudden and prolonged period of intense cold to allow the ice sheets to form.
These are bizarre conditions. Ice Age theorists have not the slightest idea how they might have come about.
Notes for Chapter 8
(22) In their comprehensive When the Earth Nearly Died, Gateway Books, Bath, 1995.
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