Frozen Earth: The Once and Future Story of Ice Ages (8 page)

Agassiz was one of those familiar with the ideas of these two men, but until his summer visit to Bex, he too had dismissed their theory as unlikely.
The holiday was a pleasant one—the scenery was idyllic, and the Agassizes found that they had much in common with the de Charpentiers.
Most evenings would find Agassiz at de Charpentier’s table with Venetz and others, enjoying their host’s hospitality and engaging in long conversations about natural history and philosophy.
We shall never know exactly what transpired during these discussions, but given de Charpentier’s and Venetz’s interests, they must have included debates about glaciers and their past behavior.
Agassiz listened to what his colleagues had to say, and undoubtedly these evening brainstorming sessions influenced his thinking.
However, with his strong
belief in observation and hands-on science, it was almost certainly the visible field evidence that really convinced him that Venetz and de Charpentier had discovered something important.
When they took him out into the Alpine valleys and showed him the moraines, erratic boulders, and glacial scratches and grooves, it was a revelation.
When he returned to Neuchâtel that autumn, he was like a blind man suddenly given sight: he saw signs of glaciation—especially erratic boulders and glacial scratches—everywhere around him.
And, together with his long-time friend from student days, the botanist Karl Schimper (the same Schimper who coined the phrase “ice age,” and who was now working with Agassiz in Neuchâtel and living in the family home), he synthesized these observations and soon came up with a theory.
With the zeal of a convert, Agassiz took up the cause of past glaciation and did his mentors one better: he proposed a period of
global
frigidity in the past, not just one in which glaciation in the Alps and a few other regions of Europe had been more extensive.

The announcement of Agassiz’s ice age theory came only a year after his sojourn with de Charpentier in Bex.
In 1837, the Natural History Society of Switzerland met in Neuchâtel, and Agassiz, as president of the society and host of the gathering, gave the introductory address.
The delegates, who expected that Agassiz would discuss fossil fish or one of his other biological interests, were in for a surprise.
After expressing his pleasure in welcoming them to Neuchâtel, and extolling the advances that were occurring in the sciences, Agassiz said that he wished to focus on a topic appropriate to the location: glaciers, moraines, and erratic boulders.
Carefully acknowledging his debt to de Charpentier and Venetz, he laid out a comprehensive ice age hypothesis that presaged his book
Studies on Glaciers,
which would be published three years later.
The address was the pivotal event that brought the idea of an ice age to the full attention of scientists.
In the context of what had gone before, it was a grandiose scheme, and it generated instant and long-lasting controversy.
What was truly new was Agassiz’s proposition that during the ice age, a great sheet of ice had
extended from the North Pole to the Mediterranean, before the Alps had even been formed.
This was very different from the idea that Alpine glaciers had extended a bit further down their valleys in the past.
It took even his friends Venetz and de Charpentier by surprise.
Furthermore, Agassiz brought zoology into the picture by proposing that the ice age had extinguished many of the Earth’s living creatures.
And implicit in his theory was the idea that there had been significant climatic variations in the Earth’s past.
The conventional wisdom at the time was that the Earth had been cooling since its creation.
Agassiz suggested instead that each geological period (already geologists had subdivided the Earth’s past into different periods based on the fossil record) had had an equable, stable, climate, but was terminated by a frigid episode, after which temperatures recovered, albeit perhaps not quite to their previous level.

One imagines that many in the audience rolled their eyes.
The scope of this scheme was too much even for de Charpentier, who was the person most responsible for convincing Agassiz that Alpine glaciation had once been much more extensive.
Agassiz, even in his enthusiasm for this new (for him) subject, recognized that there was likely to be some adverse reaction.
Toward the end of his address (which was later published) he said:

I am afraid that this approach will not be accepted by a great number of our geologists, who have well-established opinions on this subject, and the fate of this question will be that of all those that contradict traditional ideas. Whatever the opposition to this approach, it is unquestionable that the numerous and new facts mentioned above concerning the transportation of boulders, which may easily be studied in the Rhône valley and in the vicinity of Neuchâtel, have completely changed the context in which the question has been discussed up to the present time.

And in this respect he was right.
His theory was not a flight of fancy; it was carefully based on detailed field observations.
Some of the observations he discussed drew on the work of de Charpentier and Venetz,
but many were his own.
The observational skills he had learned from Cuvier in Paris served him just as well in glaciological as in fossil studies.
“Fortunately, in scientific problems, numerical majorities never settled any issue at first glance,” Agassiz told the skeptical delegates, confident of his ability to win over critics in the long run.

Three years after his lecture at the Neuchâtel meeting, in 1840, Agassiz published his carefully compiled evidence for widespread past glaciation in a large volume written in French and titled
Études sur les glaciers
—translated as
Studies on Glaciers.
It was the formal presentation of the ice age theory to the world, and it is a remarkable book, truly a tour de force.
Although he never considered studies of glaciers to be his primary scientific focus, in practice, Agassiz devoted a great deal of his time to this work, spending the better part of each summer in the Alps doing glaciological fieldwork.
In his book, in engaging language, Agassiz described in great detail the observations that he and his colleagues had recorded during those summer field seasons: the temperatures, the nature of the crevasses, the morphology of moraines, the details of the grooves and scratches on the underlying rock, and much more.
He included beautiful, if somewhat unnatural-looking, sketches of many of the glaciers they studied, often with tiny people—walkers, women in peasant dress, picnickers—or farm animals drawn in.
After cataloging the field observations, and noting how similar features occur far from the present-day glaciers, Agassiz, in a few short sentences, laid out his revolutionary conclusion:

In my opinion, the only way to account for all these facts and relate them to known geological phenomena is to assume that . . . the Earth was covered by a huge ice sheet that buried the Siberian mammoths and reached just as far south as did the phenomenon of erratic boulders. . . . It extended beyond the shorelines of the Mediterranean and of the Atlantic Ocean, and even completely covered North America and Asiatic Russia.

The frozen Siberian mammoths to which Agassiz refers in this passage had caused a great stir in Europe, and they featured significantly in
the ideas he developed about the biological effects of the ice ages.
Several reports that had filtered out from arctic Siberia described these giant mammals melting out of decomposing ice, almost perfectly preserved.
Hair, skin, and flesh were intact—in fact, polar bears fed on the thawing animals and local villagers hacked off meat for their dogs.
To Agassiz this indicated that the ice age had begun suddenly and had been a biological catastrophe.
He also mentions here erratic boulders, the same kinds of boulders that had played a major role in convincing Venetz and de Charpentier about past glaciation.
Erratics had puzzled geologists for decades and, as has already been mentioned, were at the focus of the debate between those who wanted to explain most geological features as originating in the biblical Flood and those who sought more natural explanations.
Some of the erratics in the Alps are huge, weighing thousands of tons, and they are unusual because they bear no resemblance to other rock types in their immediate vicinity.
Their great importance in Agassiz’s theory was that they are markers of the extent of ice age glaciers.

Agassiz dedicated his book to Venetz and de Charpentier.
Still, they were slighted—Agassiz did not consult them about his ideas, and they felt that his grandiose theory misrepresented some of their ideas.
No one before had postulated a truly global cold period, and no one was as enthusiastic or confident about promoting the theory as Agassiz.
In addition to showing how important ice is in shaping the landscape, Agassiz also introduced the idea that drastic climate change had occurred in the Earth’s history, and that the cold of the ice age had strongly affected life on Earth.
Each of these was a new idea, and each was controversial.

Today, Agassiz’s logic seems unassailable, and no one doubts the reality of ice ages.
To present-day scientists, as to Agassiz, the conclusion that there were great sheets of ice covering the northern continents is a straightforward outcome of the observations.
However, at the time it was a radical concept.
By the time Agassiz’s book was published, many scientists had come to accept that the Alpine glaciers had once
been somewhat more extensive than they were in the 1830s—after all, there were historical accounts as proof.
Europe was just then emerging from a period of several hundred years of cool temperatures that would later come to be known as the “Little Ice Age.”
The slightly larger Alpine glaciers described in historical accounts could explain some of the geological observations in valleys now free of ice.
But an ice age that was global in extent—that was a different matter altogether.

Agassiz’s interest in glaciation may have been stimulated in part by his biological interests.
Through his work on fossil fish, he was well aware of the paleontological evidence for periods of massive extinction in the Earth’s past.
The ice age theory provided a way to understand at least one of these events, and the frozen mammoths confirmed the extreme biological impact.
In a passage from his book that is quite poetic, he describes the ice age landscape and the effects he believed the frigid climate must have had on living things:

The development of these huge ice sheets must have led to the destruction of all organic life at the Earth’s surface. The land of Europe, previously covered with tropical vegetation and inhabited by herds of great elephants, enormous hippopotami, and gigantic carnivora, was suddenly buried under a vast expanse of ice, covering plains, lakes, seas, and plateaus alike. The movement of a powerful creation was supplanted by the silence of death. Springs dried up, streams ceased to flow, and the rays of the sun, rising over this frozen shore (if they reached it at all) were greeted only by the whistling of the northern wind and the rumbling of crevasses opening up across the surface of the huge ocean of ice.

Like many of his contemporaries, Agassiz equated life with “a powerful creation.”
Religion still had a strong influence on thinking about the origin and history of life, even if observation and reasoning had gradually overturned the teachings of the religious authorities on matters such as astronomy and even the Earth’s history.
It was to be a topic that dogged Agassiz throughout his career.
In spite of his contributions to paleontology and the evolution of fish, he would never accept Darwin’s ideas on evolution.

Agassiz’s lecture at the Neuchâtel meeting and publication of
Études sur les glaciers
were the first major parries in the debate about continental-scale glaciation.
Throughout, Agassiz never flagged in his efforts to convince others about the reality of an ice age.
The debate raged on for much longer than he, or for that matter anyone else, could have predicted.
He continued to spend summers studying Alpine ice, and in 1840, he and his colleagues set up a permanent camp and observatory on one of the major alpine glaciers in order to make continuous observations of temperature, ice movement, the nature of the rocky moraines that characterize glaciers, and many other features of these “rivers of ice.”
The little scientific encampment quickly became a magnet for visiting geologists and inquisitive travelers.
As always, Agassiz needed money for his venture.
His friend and patron from Paris days, Alexander von Humboldt, suggested to the king of Prussia that Agassiz’s glacier research was a worthy cause, and funds soon appeared.
With characteristic indifference to his finances, Agassiz spent the money almost instantly on supplies, salaries for assistants, and equipment.
He seemed always to be in debt.

Summers may have been spent on the ice, but during the rest of the year, Agassiz found time to travel widely within Europe, mainly in connection with his work on fossil fish.
He visited museums and private collections wherever they existed, usually with his faithful artist assistant, who would make detailed sketches.
His reputation grew, and he was rewarded with grants and honors, and also with long-lasting friendships with leading figures in geology and paleontology.
Agassiz also used his travels to search for signs of glacial action on the landscape throughout Europe.
Britain was considered to be the center for geological research at that time, and Agassiz, together with prominent British naturalists, made field excursions in Scotland, northern England, and Ireland.
They found abundant evidence of past glacial activity, especially in the form of moraines, erratic boulders, and glacially scratched rock surfaces.
These efforts won him some converts, but while many were willing to concede that the glaciers of the Alps had once been
more extensive, it was much more difficult to persuade them that a great ice sheet had once covered much of the British Isles.
For one thing, Britain is not a mountainous country, and glaciers were still inextricably linked to mountains in the minds of many geologists.
For another, some large-scale landscape features that were being touted as glacial features, such as lakes and valleys, seemed just too vast to have been formed by the action of ice.
It was really just a problem of imagination; most geologists simply could not imagine the scale of the long-gone continental ice sheets.
They had been several kilometers thick and hundreds to thousands of kilometers in extent.
Not a tree or a blade of grass survived where they stood; hills and valleys had been completely buried in a vast, monotonous white mantle of ice and snow.
And they had moved, slowly but inexorably flowing under their own great mass.
Agassiz once referred to glaciers as “God’s great plough.”
He used the expression as a metaphor for natural catastrophe rather than a description of glacial erosion, but it is nevertheless an apt portrayal of the power of ice to shape the landscape, to scoop out lake basins, gouge out valleys, and pile up the loose debris in great mounds and ridges.