How the Prairies were made

Here’s a story that began 2300 million years ago— the fascinating tale of a great geological squeeze that produced the wealth of the west


How the Prairies were made

Here’s a story that began 2300 million years ago— the fascinating tale of a great geological squeeze that produced the wealth of the west


THE EVENT that has done more than anything else to direct and influence the economy, geography and history of western Canada was not the first transcontinental railway, the development of Marquis wheat nor the discovery of oil. It was something only a handful of westerners has heard of. It has no official name, but some geologists call it the “big squeeze.” The stage for it was set two billion years ago and it has been molding the destiny of western Canada ever since.

It wasn’t an economic or political squeeze, although many a westerner will hotly argue that western Canada has been victimized by squeezes of this nature too. The “big squeeze,” the two-billion-year-old squeeze, was a gigantic pinching of the earth’s crust which has kneaded and molded western Canada into everything it is today.

Here is how it came about.

When the earth’s crust first cooled, it did so unevenly, leaving thick unyielding islands of rock—the geologists call them “shields” —in some regions, with thinner weaker zones of the same rock between. As the interior of the earth continued to cool, it shrank, and the outer crust had to buckle and fold to remain fitted to its interior core, producing earthquakes, mountains, volcanoes and escarpments in the process. The shields have been the earth’s unyielding cornerstones and all adjustments to the shrinking interior have had to be made by the regions of thinner weaker rock between the shields.

The earth’s biggest rigid shield is the Pacific Shield which forms the floor of the North Pacific Ocean. The second biggest is the two-million-square-mile Canadian Shield which has its centre under Hudson Bay, covers about half of Canada and gives us most of our mineral wealth. This puts western Canada between the earth’s two biggest and toughest crustal zones. And its geologic history is largely a story of how it has been repeatedly lifted, lowered, wrinkled and tilted by the squeezing of the two great shields that flank it.

In the long fascinating story of the “big squeeze” lie most of the answers to the questions that puzzled early explorers, to whom the prairies were a perplexity of nature that shouldn t exist. On a continent that had seemed all forest, hills and mountains, the prairies were all wrong. How did they and their westward flanking mountains get that way? Why, in their original state, did the plains grow only grass while practically the whole continent was forest? Why do the prairies possess a thick rich mantle of soil, while only a couple of hundred miles to the north is a barren rock land, many parts of which will hardly grow moss? And why, here so close to the drenching rains of the Pacific coast, is prairie rainfall so scant?

Only now are geologists and geographers getting to the bottom of the “big squeeze” story and beginning to unravel the answers. They still don’t all agree but out of the hectic search for oil during the past few years, there has come a new and persuasive theory about the geology of western Canada.

Every day the steel bits of the oil rigs are chewing through strata after strata of bedrock, deep beneath the prairie’s thick mantle of soil. They are bringing up in their drill cores the rock samples of a geologic pedigree so ancient that the era of the dinosaurs of a hundred million years ago is relatively speaking but yesterday. In its millions of years of geologic growing pains the part of the earth’s crust that is now the jubilee-celebrating provinces of Alberta and Saskatchewan has been covered at least a half-dozen times by vast seas. It has seen mountains come and go. It has been steaming tropical swampland, and an icecap as cold as the North Pole.

It has been under water a good deal more than it has been dry land, for this mid-continental area of the “big squeeze,” before the Rockies grew up to protect it, was a favorite spot for succeeding seas to creep in, recede and creep in again. Every sea covered its floor with sand and silt which slowly cemented itself into rock, layer upon layer, and those rock strata are still there like pages of a diary in stone preserving a record of all that happened. They tell where and how long each sea existed. They contain fossil remains, like illustrations in a textbook, which show what plants and animals lived at the time.

Each geologic epoch is marked by the coming and going of a sea, and most of them contributed something to the modern scene. Later epochs produced the Rockies, molded the present western climate, created and distributed the soil. Various earlier epochs left dinosaur bones at Red Deer, gold at Flin Flon, uranium on Lake Athabaska, coal in Drumheller Valley, and oil and gas at Leduc. The Alberta and Saskatchewan of today are an amalgam of the many geologic stages through which they have come.

Probably the first essential for an understanding of western geology is a grasp of the tremendous time periods involved in geologic history. More than two hundred years ago the first explorers reached the Canadian prairies. What is commonly regarded as the history of the Canadian west began then. But the Canadian west had existed in some form or other for a long long time before. How long? If you were to let 13,000-foot Mount Robson, the highest peak in the Canadian Rockies (so high that its top is usually hidden in cloud) represent the age of western Canada’s oldest bedrock, then a sheet of paper placed on top would represent the time that has elapsed since the arrival there of  the first white men.

Ironically, the same ultra-modern research that produced the atom bomb is now showing that the Canadian prairies lie atop some of the oldest rock of the earth’s crust that geologists have yet been able to attach a birthdate to. The prairies, therefore, though one of the newest areas of the world as far as man’s history is concerned, are actually among the oldest regions in the history of the earth itself.

Out of our new understanding of the uranium atom has come the “radioactivity clock” that measures time in millions of years instead of hours. Here is what makes it tick. A uranium crystal, as soon as it solidifies out of the molten rock that produced it, immediately begins a slow process of disintegration that changes it to lead millions of years later. One gram of uranium turns completely to lead in 7,600 million years. So, by measuring the ratio of uranium to lead in such a crystal, geophysicists have a clock which tells them how long ago the crystal and its surrounding rock solidified out of its original molten state.

The oldest rock yet dated by such techniques is in East Africa and is close to three billion years old. Next oldest, around Kirkland Lake, Ont., is two-and-a-half billion (2,500 million) years old. Close on its heels comes a granite outcrop on the Winnipeg River, Man., which the department of mines at Ottawa has determined to be 2,300 million years old. This outcrop, a hundred miles or so east of the prairies proper, belongs to the same stratum and is roughly the same age as the rock that dips downward to the west to form the foundation of the plains. 

This is the rock geologists call “preCambrian,” which means “before life,” for its lack of fossils is taken to mean that no living plants or animals existed when it, was formed.

The story of western Canada, then, can he said to have started 2,300 million years ago. But for almost four fifths of that prodigious time the west must have remained a stark and barren landscape of rock, pierced by volcanoes belching red-hot lavas and shuddering frequently with earthquakes. Whatever went on in the Canadian west and elsewhere during that near-eternity of time, there is little record of it left today, for the detailed diary of the rocks doesn’t begin until a time geologists believe to be about five hundred million years ago. At this time the long mysterious pre-Cambrian or lifeless era of the earth’s history is ending.

Pre-Cambrian North America was considerably larger than today. Hudson Bay was dry land. Greenland and the Arctic islands were all joined in one large land mass to the rest of the continent. On both sides land extended hundreds of miles out into the Atlantic and Pacific. The continent was a low plain which rose little above its surrounding seas. The strip down its centre where the western plains now lie was the lowest area.

Now the “big squeeze” began. The area of the western plains bent slowly downward and the first of many western seas flowed in. This one, the Cambrian Sea, was a long north-south neck of water three or four hundred miles wide that started at the Arctic Ocean and came out to the Pacific again in southern California. It covered what is now the area of the Rockies, most of Alberta but little of Saskatchewan. It made a large island out of Alaska, British Columbia and the Pacific United States.

The Cambrian and succeeding western seas didn’t surge in with the violence of floods. Each sea took close to fifty million years to rise and ebb; the same slow changes are being wrought today unseen. The Baltic coast of Sweden, for example, is rising about half an inch a year, a change almost imperceptible in one man’s lifetime, but in ten thousand years it will have tilted all the water out of the Baltic Sea and turned it into dry land.

Millions of years of rain eroded the original pre-Cambrian rock of the Cambrian .Sea’s shore lines, and rivers carried these sediments into the sea. On the sea bottom these sands and silts were slowly packed and cemented into rock again, so that now a readily recognizable new rock layer lies over the original pre-Cambrian wherever the Cambrian Sea extended. There are spots under the Rockies where the sedimentary rocks built up by this sea remained the longest. As the bottom built up with new rock, the weight bent it lower and the sea therefore never filled up.

By now the Canadian west had its first inhabitants for the Cambrian Sea teemed with seaweeds and the first simple forms of animal life such as marine worms, sponges, snails, jellyfish and ancient relatives of the squids. But the biggest, dominant and ruling inhabitant was a flattened, many legged hard-shelled ancestor of our present-day lobster called by scientists the trilobite. Trilobites, though most were four inches or less in length, were the world’s most numerous and most highly developed animal. They ruled the seas for a hundred million years— one hundred times as long as man has existed on earth. There were no fish yet. Nor was there anything, plant or animal, yet; living on land. Except for thunder and the beating of the sea on the shore, the west had no noise, for there was no animal with a voice, nor were there trees through which the wind could howl.

How do geologists know what creatures lived in the west so long ago? The trilobites and their neighbors died and sank to the ooze of the sea floor. There the soft parts of their bodies decayed but the skeletons or exterior shells remained as fossils and when the ooze altered to rock the fossils remained like nuts in a cake. In later ages plant leaves and stems were preserved in the same way. Often fossil preservation is so perfect that with a microscope it is possible to count the segments in the feeler of a mosquito dead for two hundred million years.

When Fish Ruled the World

The contraction of the earth’s crust doesn’t go on at a uniform rate— geologists don’t know why—and eventually a long period came during which the “big squeeze” relaxed. Western North America lifted again and the Cambrian Sea retreated. Now Alberta and Saskatchewan were dry land, but the seas were to come again and again, for this western part of the continent was like a hinge between the two great Pacific and Canadian Shields, and it was constantly being pushed up and down. At a much later age the greatest of all upheavals here produced the Rockies. Today the bowl-like section between the Rockies and the Canadian Shield near Winnipeg is known to oil geologists as the “western Canada sedimentary basin.” Actually, only its lowest pre-Cambrian rock layer is bowl-like, for succeeding seas have filled the great hollow with layers of sedimentary rock, forming the level foundation of today’s prairies. The basin is deepest at the Alberta end where three miles or more of soil and sea-made rock cover the original pre-Cambrian crust.

For perhaps a 25-million-year interval after the retreat of the Cambrian Sea, Alberta and Saskatchewan remained dry land. Then they sank again, the sea returned, and this one, the Ordovician Sea, covered much of Canada and the U. S. before its spread was halted by another period of crustal uplift.

The third sea to cover western Canada was the Silurian. Apparently it was short-lived, for the sedimentary rock layer it left behind is thin.

Now our time is around three hundred million years ago and the fourth sea slowly covered the west. Geologists know it as the Devonian, and it was a sea destined to leave an important imprint on today’s western Canadian economy. Like the Cambrian, it extended down the trough of the western plains from the Arctic to southern California. It covered all of Alberta and Saskatchewan and had a huge arm which reached across southern Manitoba into the present area of the Great Lakes.

The little trilobite was still there, but it was no longer ruler of the seas, for now the age of fishes had arrived. Devonian fossils show that fish, the first animal to have a backbone, now dominated the undersea world. Late in this Devonian age strange and very significant fish appeared. They breathed most of the time by gills, but they also had rudimentary lungs by means of which they could survive periods in air when the water in which they were living dried up and left them temporarily stranded. This lung-bearing fish lived in freshwater lakes on the uplands around the Devonian Sea and not in the sea itself. In it, nature had met the first requirement for a land dwelling air-breathing animal.

On the shores of the Devonian Sea there were now forests growing, but no flowering and seed-bearing trees and plants as we have today. Instead the forests consisted of giant, woody-stemmed fernlike plants which sometimes had stumps two feet in diameter. But except for an occasional air-breathing fish that crawled temporarily onto an inland lakeshore, the land still had no animal life as we know it today.

Across vast sections of what is now central Alberta and north into the present region of the Mackenzie Valley, the Devonian Sea for long periods was shallow and warm. These shallows teemed with minute forms of marine life, just as similar spots in today’s seas do. for the fish that eat them prefer deeper water. The shallows were close to shore and sediment from rivers built up rapidly on their bottoms. Often thick layers of the tiny marine animals that had died and dropped to the bottom were covered with silt before they could decay. The silt hardened into impervious shale, cutting off water and air permanently so they could never decay. Ages passed, more and more rock built up above, and slowly under great pressure and heat the hydrocarbons of these undecayed animals changed to oil and natural gas through a chemical reaction that geologists do not yet thoroughly understand. Even then, three hundred million years ago, an important element of western Canada’s modern economy was being created by the gigantic forces of the “big squeeze.” But one other geologic process was also at work in the Devonian Sea to give twentieth-century Alberta an oil industry.

During this period a much larger part of the world was covered by water than now; ocean currents carried the heat of the tropics throughout the globe and the whole earth had a warm, humid, maritime climate. Alberta and Saskatchewan were almost tropical and one of the effects was that corals, which now grow only in the tropics, flourished in the same shallow seas where the minute oil-producing marine animals were being entrapped in mud. Corals are plantlike animals that grow in great colonies and when they die they leave their skeletons behind. These skeletons build up into massive reefs in the sea, then when other rock is formed above them the coral reefs are pressed into layers of porous rock themselves which act as collecting reservoirs for the natural gas and oil.

Geologists know of one vast coral reef within eighty miles of the Arctic Circle in the Mackenzie Valley that is four hundred feet thick and now a third of a mile underground. Farther south in Alberta are several more reefs five hundred feet thick. You will know them too when you hear the names, because their names mark economic milestones for western Canada. They are Norman Wells, Leduc, Woodbend and Redwater. For, although later geologic ages have also produced oil in western Canada, the biggest pools are those that were trapped in the coral reefs of the Devonian Sea when no birds yet flew and the only animal on its shore was a bizarre fish that breathed air.

The “radioactivity clock” ticked off another hundred million years. In many parts of the world new seas rose and ebbed and rose again. During this long period the “big squeeze” apparently gave western Canada a rest, and most of Alberta and Saskatchewan remained high and dry. One sea during this time covered a good deal of the U. S. and sent a shallow brackish arm up into the present foothills territory of southwestern Alberta. It stayed long enough for its microscopic marine animals to produce the gas and oil pools of Turner Valley, Pincher Creek and Jumping Pound. Turner Valley, then, though discovered first and therefore looked upon as the pioneer Alberta oil field, actually belongs to a considerably more recent geologic period than the “new” fields of Leduc and Redwater.

But in other parts of the world this was a highly important geological time for it was the “Carboniferous period” —the age that produced the great coal beds of the Canadian Maritimes, Pennsylvania and England. Alberta’s coal formed much later.

On the shores of the sea that produced the oil of Turner Valley there were now air-breathing, land-dwelling animals. It had been only a short evolutionary step from the lung-breathing fish to frog-like amphibians which spent the first part of their life breathing by gills in water and their adult life as lung-breathers on land. Up until this time all life had been in the water, but now it was rapidly taking possession of the land, and with it came an important change. Fossil remains show that the first amphibians soon acquired a larynx and voice. Probably it was only a croak, but the land now had animal sounds mingling with the whine of wind and the beat of the seashore waves.

The Age of Cockroaches

Because Alberta and Saskatchewan had no seas and swamp muds in which to entrap and preserve animal remains during this Carboniferous period, there is little fossil record. From the record elsewhere, though, we know what must have been happening. Slowly, over millions of years, some amphibians developed skins of scales and began laying their eggs on land instead of water. These were the reptiles, the first animals to break completely from the sea and spend their entire lives on land. Around this time too, the first insects begin to turn up in fossils, and for some reason many of them became giants of a size unknown today. There were dragonflies with wings nearly a yard across. But the commonest insect was a cockroach vex-y similar to the one we know today—similar except for size, because they were six inches long.

They became so common that sometimes this period is known as the “age of cockroaches” instead of the “age of coal.”

The time was now two hundred million years ago. In eastern North America another crustal squeeze wrinkled and upended surface rock layers to produce the Appalachian Mountains of the Atlantic seaboard. They are eroded now until only their roots remain, but for two hundred million years they have served as a supporting ridgepole for the eastern half of the continent, and there have been no extensive oceanic invasions of the east since their appearance. But the west had not yet acquired its Rocky Mountain backbone, the “big squeeze” continued to function there, and western Canada and U. S. still had a long turbulent history of ups and downs and inflowing seas ahead of it.

The midwest entered another era of gradual submergence, the Arctic Ocean crept down again and another sea flooded Alberta, southwestern Saskatchewan and many of the western United States. The greenish-grey sandstones that built up on its floor were first identified and dated near Sundance, Wyoming, and it is known as the Sundance Sea. As it receded again, the Sundance Sea left great layers of microscopic marine life buried behind it to produce another oil-bearing stratum at Conrad in Alberta and a number in the Swift Current region of Saskatchewan.

And then, about a hundred million years ago, the last and second-greatest of all western seas began as two broad arms, one creeping down from the Arctic along what is now the Mackenzie Valley, the other reaching up from the Gulf of Mexico. Geologists have named it Cretaceous (chalklike), because this was the geologic period that produced the towering chalk sea cliff’s of England. The Cretaceous period was to leave an imperishable imprint on the west, for it gave the west its coal, its dinosaurs and the Rockies, as well as several more oil deposits including the new Pembina field and the fabulous Tar Sands of the Athabaska River.

History may soon prove that these Athabaska Tar Sands are the greatest of all the west’s natural resources except the soil itself. The sands lie on or near the surface over an area of about 30,000 square miles around McMurray on the Athabaska River, north of Edmonton, and throughout all this vast area they are saturated with oil. As yet there is no process known for extracting this oil economically from the sponge-like sands in which it is entrapped, but the problem is under intensive study and oil geologists are confident that in time the fabulously rich Tar Sands will be tapped. When the tapping begins, it will be by some process similar to mining, and not by the familiar well-drilling techniques that now produce oil. The stake is staggeringly high. Estimates of the Tar Sands oil content range from a hundred billion to three hundred billion barrels. The big Leduc-Woodbend field, as a contrast, holds only about a thousandth this much oil. If the top 300-billion-barrel figure is proven—-and many oil geologists are now predicting that it will be — the Tar Sands hold more oil by themselves than is recoverable from all the presently known oil fields of the world !

There is some dispute among the experts as to whether the Cretaceous or a previous sea actually produced this oil, for it could have seeped upward from a lower and earlier stratum of rock. But, whatever its original source, we are indebted to the sands of the Cretaceous Sea beaches fox accumulating and preserving the oil.

Palms and Figs in Alaska

The huge new Pembina field discovered in June 1953, seventy-five miles southwest of Edmonton, is similar in that it also is a Cretaceous-age sand, and not Devonian coral-reef limestone as are the producing zones at Leduc and Redwater. The oil reserves of the Pembina field when fully explored may be .second only to the Tar Sands. When fully tapped it is expected that Pembina will produce more than Redwater, Leduc and Woodbend combined are producing today.

At its greatest extent the Cretaceous Sea reached from the Arctic to the Gulf of Mexico and, in Canada, from the Rockies east almost to the Great Lakes. It lasted perhaps forty million years. With so much water covering the land again and moderating the climate, tropical conditions extended far into the Arctic. Fossils of leaves show that palms and figs grew in Alaska, breadfruit and cinnamon trees in Greenland. As the Cretaceous Sea ebbed, it left vast, warm, shallow swamps along its shores in Alberta and southern Saskatchewan. With the hot, humid climate there were dense forests growing in these swamps, making them much like tropical jungles of today. Periodically the sea returned to its coastal swamps, the trees drowned and fell, covering the swamp bottoms with tangled mats of vegetation which couldn’t decay because water and then inpouring sand cut off’ the air. By this means the undecaying plant carbons first became peat and then coal just as the animal carbons had become oil and gas during earlier western seas.

Most of the west’s Cretaceous coal is in Alberta and the Rockies; the Estevan, Sask., coal field came thirty or forty million years later. Since this "A tropical sea lay over the whole west with coral reefs to store today's oil" western coal is almost two hundred million years younger than the coal of Pennsylvania and the Maritimes, it has been subjected to less kneading and pressure, and is therefore a soft coal of poorer quality than the coals of the east. In the Rockies, though, at Banff, for example, some of this young western coal took such a mauling in the great upheaval that produced the mountains that it is close to anthracite in quality, in spite of its youthful age of one hundred million years. The Estevan coal, a mere twenty-five million years old, is the poorest quality of all.

The same swamps that produced Alberta’s coal also provided the two requirements food and buoyancy — that permitted small lizard-like reptiles to evolve over a period of about a hundred million years into the gigantic, grotesque Frankenstein monsters we call “dinosaurs.” The biggest dinosaurs approached ninety feet in length and weighed perhaps twenty tons. To maintain such bulk, a tremendous quantity of food was necessary, and this requirement was admirably met by the Alberta swamps and their tropical climate which permitted rapid year-round growth of plants and trees. But because of their very size they had an enemy that no other animal except the whale has ever had to contend with that enemy was gravity. Some dinosaurs became so big that their legs could support them for only short periods on land. Just as the whale solved this problem by taking to the sea, the dinosaurs solved it by living in shallow lakes and swamps where they were partially supported by the buoyancy of the water.

Many swampy plains of the world had dinosaurs during the Cretaceous age, but the evidence of the fossils strongly suggests that nowhere were conditions more suitable nor the animals more abundant than in Alberta. One twenty-five-mile stretch of the Red Deer River valley near Brooks has alone produced remains of more than a hundred dinosaurs, thirty-six of them complete or almost-complete skeletons. One square mile near Sand Creek has provided museums with thirteen dinosaur skeletons or partial skeletons. Dinosaur fossils have also been found along the Milk River in southern Alberta and in the Cypress Hills region of southwestern Saskatchewan.

Dinosaurs reached their peak about a hundred million years ago. At that time the Alberta and Saskatchewan swamplands would have been a fearsome and inhospitable place to go strolling or boating. The first of the big dinosaurs were plant-eaters and probably as gentle and peace-loving as cows. But great flesh-eating dinosaurs soon appeared, probably as ferocious as they were big, and it is undoubtedly a blessing of the evolutionary process that there were no men yet on earth to face them.

One of the commonest dinosaurs in western Canada was apparently a huge plant-eater named Corythosaurus. It approached thirty-five feet in length, had feet like small tree trunks that left tracks a foot or so across, but the brain that controlled its fifteen-ton body was smaller than the brain of a fox terrier. When Corythosaurus clambered out of the water and stood on land, you would have needed a twenty-five-foot ladder to get on his back.

Somewhat smaller, but more grotesque and formidable, was Styracosaurus, one of several Albertan horned dinosaurs. To protect its soft and vulnerable neck, Styracosaurus had a huge bone shield projecting from the base of the skull like a gigantic cloak back to the shoulder. Around the rim of this neck shield was a frightful array of long sharp horns or spines. Including this projecting shield, Styracosaurus had a head six feet long. There was also often a nose horn which made this and the other horned dinosaurs resemble the rhinoceros of today.

But the huge plant-eaters like Corythosaurus and Styracosaurus, in spite of their tremendous size, were slow-moving, slow-witted and easy prey for the ferocious and agile flesh-eating dinosaurs. The mightiest and most formidable flesh-eating animal that ever existed on earth was undoubtedly Tyrannosaurus rex—“king of the tyrant dinosaurs.” Scientists are not certain that Tyrannosaurus lived in Alberta or Saskatchewan, although he probably did, for his bones have been found nearby in Montana. But they do know that a version only slightly smaller named Gorgosaurus was common in Alberta. Tyrannosaurus was fifty feet long, Gorgosaurus slightly under forty. Both walked upright on two legs and were apparently nimble on their feet. They had huge heads four feet or more long but they were designed for teeth not brains. Each tooth was as big as a six-inch dagger and they had around fifty of them, in a mouth almost large enough to take a man in one snap.

How the Rockies Were Born

These gigantic flesh-eaters must have made life miserable for their vegetarian dinosaur cousins. Many Alberta dinosaur skeletons in the Royal Ontario Museum at Toronto and elsewhere show bones as big as fence posts that have knitted and healed after being fractured in dinosaur battles of one hundred million years ago. Two dinosaurs weighing ten or twenty tons each, coming together in battle, probably shook the earth like two locomotives crashing head-on.

But as the great interior Cretaceous Sea slowly ebbed, there were much greater forces shaking the land of the west. In previous cycles of uplift, the “big squeeze” had lifted the land sufficiently to spill out the sea, then the uplift had halted. But this time pressure from the west continued for millions of years after the sea had disappeared. The present area of the plains was now reinforced with one to three miles of rock laid down during its many seas, but the British Columbia rock crust was thinner because seas had been less frequent there. As the “big squeeze” continued, something somewhere had to yield. The yielding occurred in the weaker crustal strata of British Columbia, in fact along the Pacific everywhere from Alaska to Central America. The rock layers buckled and shattered, often they were tilted up almost on end. And the first generation of the Rockies was horn.

It happened very slowly, so slowly that had man been living there then he would have noted no change in a lifetime. But the Alberta and Saskatchewan area shook frequently with earthquakes. The dinosaurs, if their meagre brains were big enough to know fear, must have listened fearfully to the frequent rumbling of the earth beneath their ponderous feet. And well they might, for it was signaling the end of the hundred-million-year dynasty on earth. Man, before he can boast that he has been master of the earth as long, has another ninety-nine million years to go.

With the rise of the first Rockies, the dinosaurs disappeared into extinction. There had been several hundred different species and why they died out so rapidly and so completely without leaving descendants today is a mystery that has the dinosaur experts baffled.

One widely held theory is that the Rockies cut off moist winds from the Pacific, the swamps dried up, and the climate turned colder and drier. The dinosaurs by now were so closely adjusted, physically and mentally, to their swamp environment that they couldn’t adapt to the new conditions. Perhaps they were too big of body anyway to ever live permanently on dry land. When the climate became one of winter and summer, instead of summer the year round, all coldblooded reptiles had to develop the hibernating habit to survive, and probably the dinosaurs were too big to find hibernating hideaways. Whatever the final cause of their extinction, the fundamental conflict between their weight and the earth’s gravity must have entered into it. The fact that nature has never produced animals as big since is taken by some scientists as proof that the dinosaurs simply became too big to survive.

Some scientists see in the disappearance of the dinosaurs a victory of brains over brawn. For at this time small hedgehog-like animals—the first of the mammals—were appearing. They were warm-blooded and better equipped to survive in a climate steadily turning colder. They carried their young within them, instead of laying eggs as the dinosaur did and leaving them at the mercy of any egg-eating animal that came along. And they had a better brain. With plenty of huge dinosaur eggs for food and a brain to keep them out of dangerous situations, the first small mammals prospered at the dinosaurs’ expense.

Dinosaurs disappeared throughout the world at about the same time, for the continental seas all declined together. But the slowly ebbing swamplands of Alberta were probably the site of the dinosaurs’ last stand, for dinosaur bones found around Drumheller are younger by thousands of years than any found elsewhere in the world.

The age of mammals had arrived. The stage was getting set for the arrival of man. The central North American plains had seen their last great sea, although the time is still fifty million years ago.

Alligators in Saskatchewan

With the Rockies keeping out the moist warm air of the Pacific, the climate of the central plains came under the influence of the Arctic and stayed cool and dry. The old fern-like plants and trees that grew the year round were killed by the cold winters. New plants and trees better fitted for the changed conditions developed in western North America and in several other parts of the world where the climate was similar. They were trees that shed their leaves for the winter, and flowering plants that produced seeds in which life could be suspended during the annual season of cold. It was an important change, for with seeds came fruit, nuts and vegetables, the concentrated plant foods that became so important in the diets of later animals. But there were still only a few rudimentary grasses and wild grains.

For a long time after the rise of the first Rockies the Canadian west was covered with forest, and the trees were the beeches, birches, maples and oaks familiar today.

Meanwhile the patient, relentless work of rain, streams, frost and glaciers slowly wore down the Rockies until, by twenty-five million years ago, only rows of hills remained. Pacific air could once more circulate freely deep into the continent, the Arctic winters receded northward and a humid, subtropical climate like that of modern Louisiana again claimed the west. Palm trees and alligators came again to southern Saskatchewan. Once more conditions were right for the laying down of coal beds, and the coal mined at Estevan belongs to this fairly recent geologic age.

But the “big squeeze” resumed and a second generation of the Rockies slowly rose—the young, high, craggy and little-eroded Rockies we still have today. During this same period the squeeze was responsible for smaller local uplifts farther east on the plains, producing Cypress Hills, Sweet Grass Hills and Bearpaw Mountains. The climate of the plains turned cool and dry again. The subtropical trees and plants died out. But this time forests didn’t return, for a vigorous new branch of the plant world better fitted to take possession of the earth’s dried regions had appeared. It was the grasses.

This development and spread of the grasses about fifteen million years ago was one of the great milestones in the history of life on earth. The great grass family, father of all modern grain and forage crops, was destined to become the basic food of man. It spread to many parts of the world where the soil was rich but the climate relatively dry, creating prairies and velds. One of the first of these grasslands appeared in the lee of the newly risen second generation of the Rockies, and the prairies as we know them today were born.

The western landscape was by then very similar to today’s but its animal life was very different. Mammals like the wild horse, camel, rhinoceros and elephants, which today we think of as being exotic Asian and African forms, were then living in western North America; in fact most of them first appeared there.

One of the most interesting and most important animals to come out of western North America was the horse. Hundreds of fossil skeletons show how it changed gradually from a small, four-toed mammal the size of a fox terrier to the big single-toed beast of burden we know today. The fossil story of the horse also shows the dramatic body adjustments that had to be made when the west changed from subtropical swampland to prairie grassland. It is one of the most plainly read stories of animal evolution, for there are no “missing links.” Much of the story was enacted in southern Saskatchewan and Alberta, and many skeletons of primitive horses have been found embedded in rock of Saskatchewan’s Cypress Hills.

The first horse ancestor was Eohippus, the “dawn horse,” more like a dog than a horse, which scurried about the swampy woodlands of Saskatchewan and Alberta fifty million years ago soon after the dinosaurs disappeared. It had small, low-crowned teeth for chewing tender leaves, and broad, four-toed feet for support on soft marshy ground.

In the rock strata of twenty million years later (thirty million years ago) there are no signs of Eohippus, but there is another horse very similar which obviously sprang from Eohippus.

It is Mesohippus, the “in-between horse,” the size of a small sheep and looking more horselike. It still walked on all four of its toes, but the middle toe of each foot had grown much larger and had a big thick toenail.

The woodlands disappeared and the prairies came. Mesohippus also disappeared and in its place is Protohippus, the “just-before horse.” Protohippus was the size of a small pony. The prairie ground was now hard and the evolving horse didn’t need a broad foot. What it did need was the ability to run fast because there was nowhere now to hide from enemies. To give it speed it now ran on one toe in which the toenail had become a sharp hoof like the cleat on an athlete’s boot. The other toes had shrunk until only remnants under the skin remained. Protohippus had also changed from a tree-browsing to a grass-grazing animal. Grass is a harsher food that wears teeth faster, and the teeth of Protohippus, like those of the modern horse, had much bigger grinding surfaces, thicker enamel and, to offset wear, they continued to grow through life.

Equus, the modern horse, appeared about five million years ago, still carrying above each hoof the tiny rudimentary bones of its long-disused other toes. During the last million years there were at least ten different horse species trotting over the Canadian and U. S. plains. Sometime during this period the continent rose slightly, producing a land bridge between Alaska and Siberia, and some of these horses migrated to Asia. Then, for some reason unknown, the American horses became extinct, perhaps through an epidemic like hoof-and-mouth disease. Fortunately for man, the horse was now well established in Asia where it was later domesticated. Early Spanish explorers brought the horse again to North America, but not until scientists began digging up the fossil bones of the prairies early in this century was it realized that the horse had been brought back to its birthplace.

Many other animals now looked upon as entirely non-Canadian, have the same strange history—an origin on the Canadian and U. S. prairies, then extinction here while their emigrant kin have lived on in other parts of the world.

A long-necked ancestor of the camel which has left its bones in the Cypress Hills of southern Saskatchewan was, judging from the number of fossil remains it has left, one of the commonest animals on the prairies ten million years ago. It too migrated to Asia, then died out on the plains where it was born. A camel skull found recently in a Utah cave indicates that camels still lived in the west as recently as 25,000 years ago.

The rhinoceros also originated on the North American plains. Though its bones have been identified in an outcrop of rock southeast of Swift Current, it is believed to have lived farther south and was probably never common on the Canadian prairies.

Two primitive elephants, the mastadon and mammoth, lived on the prairies, but with them the story is reversed—they migrated here from Asia. The mammoth, a gigantic, shaggy-haired brute ten feet tall with teeth weighing four pounds each, still roamed the west as recently as 25,000 years ago and then it disappeared.

The buffalo, also an immigrant from Asia, was a latecomer that arrived within the last 50,000 years. At one time there were several buffalo species in the west, one of them a giant with a six-foot spread of horns.

Of all these large grazing mammals, only one—the buffalo—still survived when white men first saw the plains. For very recently, as geologists measure time, the continent came through a period of violent change and destruction, a time of harsh trial and testing for everything living on it.

It began about one million years ago. Little by little the winds that blew down into Saskatchewan and Alberta from the north grew colder and sharper. In the Northwest Territories west of Hudson Bay more snow fell each winter than the succeeding summer could melt. The snows of innumerable winters slowly piled up and compressed themselves into a steadily thickening icecap. As pressure at the centre increased, the edges flowed outward in an ever widening circle. The great glacier, its fissured front a perpendicular white wall that towered a mile above the prairie, crunched its way south over Saskatchewan and Alberta like a gigantic bulldozer, pushing soil, forests and great rocks before it. For 50,000 years it advanced until its front was well south of the Canadian - U. S. border, and the Canadian prairie provinces were almost totally covered. Then the climate turned milder and the ice front slowly melted back until eventually even its far north core had disappeared.

Four times during the past million years this glacier has crept down from the north across the prairies, destroying or driving all life before it. And four times it has melted again and let life return to the plains.

What caused this? The geologists and climatologists have only theories. Some believe that warmth from the sun is periodically reduced by sunspots. Some suggest that volcanoes filled the atmosphere with fine ash which filtered out the sun’s warmth. Others claim that the earth wobbles on its axis and at times tilts away from the sun.

Each glacial period wiped out most of the signs left by previous glaciers, so there is a detailed record only for the last of the four, the one that sculptured the landscape we see today.

It started its ponderous southward march from west of Hudson Ray about 100,000 years ago. (None of them came from the North Pole because cold alone doesn’t produce a glacier; there must be heavy snowfall as well.) Arctic animals like polar bears and musk oxen moved south before it. They didn’t have to hurry, for the ice moved possibly only fifty feet a year and even snails could keep ahead of it. Thus, no animal needed to be actually engulfed by the ice, yet the glaciers, by drastically reducing habitat and crowding species into the south, must have been a big factor in the extinction of all large prairie mammals except the buffalo.

The fourth and hist glacier entered Saskatchewan at its northeast corner. At this time the Canadian Shield, which covers the northern third of Alberta and Saskatchewan, was well covered with soil and its pre-Cambrian rock surface was worn smooth so that it contained few or no lake basins. As the glacier moved south, boulders froze into its surface, turning it into a gigantic sheet of sandpaper. Wherever the Shield was slightly softer it dug into the rock itself, producing thousands of basins which became lakes thousands of years later when the ice receded.

Where the Soil Came From

Ry the time the glacier reached the plains it was shoving mountains of humus, sand and pulverized rock before it, and the Canadian Shield behind in the north was scraped clean. Then it began scraping up vast quantities of new soil-making materials—the clays and limes which had been laid down as limestone and shales by the western seas of ages past. All these materials were kneaded and mixed to produce the rich prairie soils of today. Periodically the glacier rode over the top and left great mounds of these soils behind.

About 15,000 years ago, when the ice front was several hundred miles south of the U. S. border, the last glacier began to recede. As it melted back across the Canadian prairies, the towering ice wall cut off normal drainage to Hudson Ray and large lakes of meltwater accumulated. Most of these old glacial drainage systems are now dried up, but remnants of some remain. Last Mountain Lake north of Regina and the valley, now dry, which connects its southern end with the South Saskatchewan River at Elbow, is one. So is the alkaline lake chain, Chaplin Lake to Rig Muddy, which runs west and south of Moose Jaw.

The best prairie soils are those that acquired more than their share of moisture-holding clays because they were once silt-covered bottoms of glacial lakes. The Regina Plain, best wheatland in Saskatchewan, owes its level topography and rich soil to the fact it was a lake bed for a thousand or so years. Other rich lake-bed soils are the “Sceptre” soils along the South Saskatchewan River from Elbow west, the “Blaine Lake” soils east of North Battleford, the “Melfort” soils of the Carrot River valley, and “Elstow” soils southwest of Saskatoon. The “Melfort” soil belt was produced by an arm of Lake Agassiz, the largest of all western glacial lakes. It covered southern Manitoba, was five times the size of Lake Superior at its biggest stage, and portions of it remain as Lakes Winnipeg, Winnipegosis and Manitoba.

Taken as a whole, the rich brown soils of the prairies form Canada’s most valuable natural asset. They are the source of more than ten percent of the nation’s total dollar-value of production, alone contributing more to Canada’s economy than all the nation’s forests, or its minerals. Yet they were born, ironically, out of a grinding devastation of ice that swept all life before it, then left the basis for a richer life in its wake.

What of the future? Will new glaciers and new seas overwhelm the Canadian west in the ages ahead?

Geophysicists say we are still living in the tail end of the last ice age. One tenth of the earth’s surface is still covered by the glaciers that began to recede ten thousand years ago. They are the icecaps of Greenland and Antarctica, both of which are countries where vegetation once thrived. These massive ice sheets will probably continue to melt, pouring their meltwater into the oceans until they are more than a hundred feet deeper than today. New York, London, Halifax, Vancouver and possibly Montreal will be submerged. Rut this will be a rising of the oceans, not a submergence of the land, and therefore western cities like Regina, Saskatoon, Edmonton and Calgary, whose areas have been drowned by seas so many times before, will this time remain high and dry.

Rut in the more distant future violent change will come again to the west. According to geophysicists, there is every reason to expect that, something like fifty thousand years from now when present icecaps have melted, the glacial cycle will be repeated and another ice mass will begin its sluggish and irresistible flow to add another cataclysmic chapter to the turbulent geologic history of the west.

Meanwhile, recurring west - coast earthquakes and the recent discovery that parts of California are arching upward three feet a century leave no doubt that the “big squeeze” also still goes on. Geologists regard eastern North America as an “old” land that has geologically settled down, but the west is still a region of crustal uneasiness and instability. The central plain, the “hinge” of the “big squeeze,” is bolstered now by one to three miles of overlying rock laid down by its long series of seas. Will it bend again and let the seas take over once more? No one can possibly say.

Rut one forecast can be much more confidently made. The Rockies now are still high and young, not yet rasped down by the chiseling forces of wind, frost and rain. As a result, the climate of Alberta and Saskatchewan is at a stage in which it is drier and colder than the average of its long geologic history. Eventually the Rockies will go, Pacific rain clouds will sweep unhindered, the dry-weather-loving grasses will give way to moisture-loving forest, and the prairies will he gone.

For only in man’s meagre dimension of time is the earth’s landscape eternal. In the eons of geologic time mountains, seas and even continents must come and go.