At a much later period a new collection of terranes from widely varied sources started moving in to complete the major outline of Alaska, and they arrived with such titanic force that an entire new mountain range was thrown up, about three hundred miles south of the older Brooks Range and parallel to it. This was the Alaska Range, a majestic row of rugged peaks which, because they are so much younger than the Brooks, have not yet been eroded down to stumps. Young, soaring, vivid in form, tremendous in reach, these peaks stab the frosty air to heights of twelve and thirteen, nineteen and twenty thousand feet. Denali, the glory of Alaska, soars to more than twenty thousand and is one of the most compelling mountains in the Americas.
Old Brooks and young Alaska, these two ranges form the twin backbones of the region and give Alaska a wilderness of mighty peaks, some of which have yet to feel the foot of man. Sometimes, when seen from the air, Alaska seems nothing but peaks, thousands of them, many not even named, and in such varied snow-covered profusion that Alaska could well be called the land of mountains.
And each one was formed by some segment of the Pacific Plate bulldozing its way into the North American Plate, submerging along the edge, and causing such tremendous commotion and movement offerees that the great mountains erupted as a consequence.
When one looks at the glorious mountains of Alaska he sees proof of the power of the Pacific Plate as it noses its way north and east, and if today he visits Yakutat, he can observe the plate pushing into Alaska at the steady rate of two inches a year.
As we shall see later, this produces large earthquakes in the area, and nearby Mount St. Elias, 18,008 feet, grows taller year by year.
But there is another region in Alaska which shows the operations of the great Pacific Plate at even more instructive advantage. West of what finally became mainland Alaska there was originally only water, and turbulent water it was, for here an arctic sea, the Bering, met an ocean, the Pacific, and dark waves signaled their meeting, a haunt of seal and walrus, of sea birds that skimmed the surface of the water seeking fish, and of one of the most delightful creatures nature provides, the sleek sea otter whose round bewhiskered face looks almost exactly like that of some roguish old man.
In these waters, too, swam the fish that would ultimately make Alaska famous, the salmon, whose life story will prove compelling.
Here plates collided to produce a magnificent chain of islands, the Aleutians, and two of nature's most dramatic manifestations: earthquakes and volcanoes. In any century, considering the entire surface of the earth, of all the earthquakes that occur, three or four out of the ten most powerful will occur along the Aleutians or close to them, and some of the most destructive are those which take place deep within the bosom of the ocean, for then landslides of gigantic dimension displace millions of tons of submarine earth. This powerful disruption creates immense underwater waves which manifest themselves as tidal waves, more properly tsunamis, which course through the entire Pacific Ocean at speeds that can surpass five hundred miles an hour.
So a submarine earthquake in the Aleutians poses a potential danger to the Hawaiian Islands, because six or seven hours after it occurs in Alaska, its resulting tsunami can strike Hawaii with devastating power. Silently, never causing a surface wave much over three feet high, the tsunami transmits its power with vast radiating force, and if it encounters no obstruction on its way, it runs on and on until it finally dissipates. But if it does bump into an island, the waves that have been no more than three feet high come on quietly but relentlessly until they cover the land to a depth of five or six feet. This flooding, of itself, does little damage, but when these accumulated waters rush back off the land to regain the sea, the destruction and loss of life can be tremendous.
The earthquakes produced along the Aleutian chain are endless, thousands in a century, but most of them, fortunately, are only minor, and although many submarine ones produce tsunamis, only rarely are they of such magnitude as to threaten Hawaii, but, as we shall see, they do often produce local tidal waves of great destructive power.
The same tectonic forces which create situations conducive to earthquake activity produce volcanoes, and thus the Aleutians become one of the world's most active volcanic centers, with some forty volcanoes stringing along the chain. It is a rare island that does not have its crater, and some craters appear not in connection with established islands, but as lonely spots in the middle of the sea. Some stand on the verge of becoming islands, smoking above the surface for a hundred years, subsiding for half a century, then peeking their sulfurous heads above the waves to throw flames in the night.
Because of the profusion of volcanic activity along the Aleutians a bubbling cauldron, really Alaska holds an honored place, perhaps the preeminent place in the Rim of Fire, that unbroken chain of volcanoes which circles the Pacific Ocean wherever the Pacific Plate comes into violent contact with other plates.
Starting at Tierra del Fuego at the southern tip of South America, the volcanoes come up the western side of the continent (Cotopaxi, Lascar, Misti), then along Mexico (Popocatepetl, Ixtaccihuatl, Orizaba, Paracutin) and into the Pacific states (Lassen, Hood, St. Helens, Rainier), and then the Aleutians, where they are so ordinary that their names, often commemorating Russian sailors, are not widely known.
The Rim of Fire continues dramatically along the east coast of Asia, with many volcanoes in Kamchatka, Mount Fuji and others in Japan, a stunning array in Indonesia and on to New Zealand with its beautiful Ruapehu and Tongariro.
And, as if to prove the capacity of this area to breed violent activity, in the middle of the Pacific Ocean rise the two magnificent Hawaiian volcanoes Mauna Loa and Mauna Kea. Considering the platform from which they rise, far beneath the surface of the ocean, they are among the tallest mountains on earth and certainly the highest volcanoes.
But none of the many along the rim are more compactly arranged and fascinating to study than those dozens that cluster along the Aleutian chain; indeed, these islands could well be preserved as a universal park to demonstrate to the world the majesty of the volcano and the power of plate action.
WHAT IS THE FUTURE OF ALASKA, GEOLOGICALLY Speaking? For interesting reasons which will be developed, we can expect that at some distant time perhaps twenty thousand years from now Alaska will once again be joined to Asia by the historic land bridge, while land communication to the rest of the United States may be cut.
And since the great plates of the earth never rest, we can anticipate the arrival at Alaska of additional terranes, but these may not lurch onto the scene for several million years, if then. .One future event will cause comment, if people are living then who remember history.
The city of Los Angeles is now some twenty-four hundred miles south of central Alaska, and since it is moving slowly northward as the San Andreas fault slides irresistibly along, the city is destined eventually to become part of Alaska. If the movement is two inches a year, which it often is, we can expect Los Angeles to arrive off Anchorage in about seventy-six million years, which was about the time that was required for some of the other terranes from the south to move into position against the ancestral nucleus.
So Alaska must be viewed as having two characteristics: great beauty but also implacable hostility. Its intricate mosaic of disparate terranes has produced lofty mountains, unequaled volcanoes and glaciers. But in the early days the land was not hospitable to settlers. Animals and human beings who came to this promontory had to adjust to profound cold, great distances and meager food supplies, which meant that the men and women who survived would always be a somewhat special breed: adventurous, heroic, willing to contest the great winds, the endless nights, the freezing winters, the cruel and never-ending search for food. They would be people who lived close to the unrelenting land both because they had to and because they reveled in the challenge.
Alaska would always call forth the best in a small handful of daring men and women, but those who did not relish the contest or who refused to obey the harsh rules w
hich governed it would find the bitterly cold land repellent and would flee it if they could retreat before it killed them.
The number of settlers was never very large, for in the icy tundra of the north slope only a few thousand at a time would challenge the rigors; in the grand valleys between the mountain ranges not many would adjust to the radical alternations of climate; and even in the easier enclaves and islands to the south people would not cluster when with far less effort they could enjoy the more inviting climate of California.
But because Alaska lay at the crossroads joining North America and Asia, it would always be important; and since it dominated these crossroads, it would enjoy a significance which only the brightest intellects of the region would appreciate. There would always be a few Russians who understood the unique value of Alaska, a few Americans who appreciated its enormous importance, and upon these knowing ones would depend the history of this strange, compelling land.
II - THE ICE CASTLE
At various times in the ancient past, for a complex set of reasons which have yet to be untangled, ice began to collect at the poles in vast quantities, growing ever thicker and more extensive, until it created immense ice sheets which encroached on surrounding continents. Snow fell at such a rate that it could not melt as it would have done under ordinary circumstances. Instead, it piled to unprecedented heights, and the pressure from that on top was so considerable that the snow at the bottom was turned into ice, and as snow continued to fall, ice continued to form, until it stood in certain places more than a mile and a half thick. The weight was so oppressive and inescapable that certain parts of the earth's surface, heavily encumbered, began to sink perceptibly, so that land which once stood well above the surface of the oceans was now depressed to sea level or below. If in any given region this enormous accumulation of ice rested on a flat plateau, a huge and quietly spreading ice cap resulted, but since the surface of the earth, because of the violent way in which it had been formed, was irregular, with mountains and valleys predominating, the ice which found itself on a slope, as most of it did, began slowly to move, under the force of gravity, to lower elevations, and as it did, its weight was so great that it dragged along with it a mass of rubble composed of sand, gravel, rocks and, occasionally, boulders of gigantic size. This lateral transport of material occurred wherever the ice field was in motion, but when a snowfield accumulated on some high plateau and began to send glaciers down valleys which might have steep gradients, the consequences could be dramatic, for then the ice formed a moving glacier which routed out the bottom of the valley and scored the sides with streaks so pronounced that they would still be visible eons later.
These glaciers could not run forever; as they probed into lower and warmer land their ends began to melt, forming massive rivers which carried ice and silt and boulders to the sea. Such glacial rivers were a milky white, colored by the flecks of rock they carried, and as they dropped their stony burden, land was formed from the detritus of the melting ice field.
If the valley down which the glacier came ended at the shoreline, the towering face of ice would come right to the edge of the ocean, where in due time fragments of the glacier, sometimes as big as cathedrals, sometimes bigger, would break away with resounding cracks that would reverberate through the air for many miles as the resulting iceberg crashed into the ocean, where it would ride as an independent entity for months and even decades. Then it became a thing of majestic beauty, with sunlight glistening on its towering spires, with waves playing about its feet, and with primitive birds saluting it as they sped by.
In time, of course, the great icebergs would melt, adding their water to the ocean, and clouds passing overhead would lift this water, carry it inland, and deposit it as fresh snow upon the ever-growing ice field that fed the glaciers.
Normally, if such a word can be applied to any natural function which by its character must vary, an equilibrium between the formation of snow and its removal as it melted into water was maintained, so that the ice fields did not invade terrains which traditionally were not ice-covered, but during what have been called the ice ages, this equilibrium was disturbed, with ice forming much faster than it could be dissipated by melting, and for centuries learned men have been fascinated by the mystery of what caused this imbalance.
Seven or eight potential factors have been suggested to explain ice ages: the inclination of the earth's axis toward the sun, for if any portion of the earth was removed even slightly from the heat of the sun, ice would result; the wandering of the earth's poles, for they are not fixed and have been located in some periods close to the present equator; the elliptical path of the earth around the sun, which deviates so substantially that the earth's distance from the sun varies greatly during the course of a year; changes within the center of the sun itself causing the value of whatever heat is disseminated to vary; chemical changes in the atmosphere; physical changes in the oceans; and other inventive and enticing possibilities.
The time span of these variables can be as short as a calendar year or as long as fifty to a hundred thousand years, so to devise a theory which explains how they interact to produce an ice age is obviously complex and has not yet been solved.
To take an easy example, if four different factors in an intricate problem operate in cycles of 13, 17, 23 and 37 years respectively, and if all have to coincide to produce the desired result, you might have to wait 188,071 years (13xl7x23x 37) before everything fell together. But if you can get fairly satisfactory results when only the first two factors coincide, you could confidently expect that result in 221 years (13x17).
There is now an attractive theory that in relatively recent times, periods of extensive glaciations over Europe and North America have occurred in obedience to three unexplained cycles of about one hundred thousand years-, forty-one thousand and twenty-two thousand.
At these intervals, for reasons not fully understood, the ice begins to accumulate and expand, covering areas which for thousands of years have been clear of ice fields and glaciers. The causes are natural and may in time be understood; in fact, science-fiction writers dream that they may even become manageable, so that future ice ages need not extend so far south into Europe and North America as they have in the past.
Strangely, although a permanent ice cap came in time to cover the South Pole, which was a continent, none developed at the North, which was a sea. The glaciers which covered North America stemmed from caps in Canada; those that submerged Europe, from the Scandinavian countries; and those which struck Russia, from sites near the Barents Sea. And because the movement of ice in North America was mainly to the south, Alaska would never lie under a massive ice sheet; Wisconsin and Massachusetts would, and so would a dozen other states, but not Alaska. It would become known as a cold and barren land covered with ice and snow, but it would never know in all its millennia as much ice as a more habitable state like Connecticut had once known or Massachusetts and New York.
The world has known many ice ages, two of which lasted an appalling number of millennia when much of Europe and North America lay crushed beneath monstrous thicknesses of ice. Then winds howled across endless wastes and freezing night seemed perpetual. When the sun did appear, it was unproductive, glistening down upon dead icy surfaces. All visible living things perished: grasses and trees, worms and insects, fish and animals. Desolation ruled, and during these vast periods of frozen waste it must have seemed as if warmth and life could never return.
But each protracted ice age was followed by joyous intervals of equal length when the ice mysteriously retreated to release from its frozen prison an earth bursting with energy and the capacity to restore life in all its manifestations. Grasses flourished to feed the animals that hurried back. Trees grew, some bearing fruits. Fields, nourished with minerals long unused, bor'e lavish crops, and birds sang. The future Wisconsin's and Austrias exploded into life as the sun brought back warmth and well-being. The world had returned to abundant life.
These first two grea
t ice ages began to evolve so very long ago, say about seven hundred million years, that they need not concern us, but some two million years ago when the historical record was about to begin, a series of much briefer ice ages arrived, and their dates, extents and characteristics have been so well defined that they have been given distinctive names: Nebraskan, Kansan, Illinoian, Wisconsin in Europe: Gunz, Mindel, Riss, Wiirm with the last segment in each group subdivided into three parts, making six in all. The names can be ignored; they will not be referred to again, but two significant facts cannot be ignored: the last of these six recent ice ages ended only fourteen thousand years ago, with glacial remnants existing as late as seven thousand years ago, so that the men and women then living in North America experienced one of the ice ages. And the normal extension and retraction of the polar ice cap indicates that about twenty thousand years from now we may anticipate another icy incursion to areas as far south as New York, Iowa and spots in between.
But of course, if history is any predictor, Alaska at that time will be ice-free and a relatively attractive place in which the residents of our Northern states can seek refuge.
EVEN THOUGH ALASKA DID ESCAPE BEING SUBMERGED BY these vast weights of frozen water, it was attacked by isolated glaciers which formed in its own mountains, and some were of substantial size. In the northern areas during one of the lesser ice ages, an icy finger covered the Brooks Range, carving and readjusting those mountains and building beautiful valleys. Much later, glaciers of some size came into the Alaska Range to the south, and even today huge ice fields with their probing glaciers exist in the extreme southern regions, where constant precipitation brought in by Pacific winds keeps the fields covered with snow, which packs down to form ice just as it did when the first Alaskan ice fields formed.