Lens to the Natural World. Kenneth H. Olson
Someone has said that a highbrow or intellectual is a person who looks at a sausage and thinks of Picasso. In a similar vein to that rather clever remark, a paleontologist looks at the ordinary crust of the earth with its rocky layers, which are as common and mundane as sausage is to breakfast, and sees therein the record of life on earth. All that separates the various beings in the passage of a billion years is time, and what is that? Henry David Thoreau wrote, “Time is but the stream I go a-fishing in. I drink at it; but while I drink I see the sandy bottom and detect how shallow it is. Its thin current slides away, but eternity remains. I would drink deeper, fish in the sky whose bottom is pebbly with stars.” He saw beyond mere measurement and chronology to time’s mystery.
The nature of time baffles all of us. A joke in paleontological circles concerns people on tour through a natural history museum in the southwestern United States. The guide told them, “These dinosaur skeletons, some of the earliest ones, are 200 million and three years old!” Everyone was amazed. “How can you be so precise?” they asked. He replied, “Well, when I got the job, they told me they were 200 million years old—and that was three years ago.”
It is nearly impossible to hold in the mind numbers of this magnitude and to see ourselves in relation to them. Of course, some make no attempt, something like the sailor who was asked the distance to the sun; he said, “It’s far enough away so that it will not interfere with anything I want to do in the Navy.” Locating our context in both space and time is central to our humanity but is far from easy. A sign outside an astronomy lab reads, “Caution: The study of astronomy may be hazardous to your sense of self-importance!” Concepts of deep time, like those of deep space, can be threatening for many people.
It is intimidating to consider that so much of earth’s history has gone on before we arrived. After all, we are accustomed to thinking and acting as if everything revolved around us. It used to be said of Frederick the Great that he loved music, but that this was not so much music as it was the flute, and not so much the flute as his flute. The story of the Garden of Eden is about the egocentricity of human nature. The Greek myth of Icarus, in pride flying too close to the sun, is concerned with it also. Bertrand Russell once said, “Every man would like to be God, if it were possible; some few find it difficult to admit the impossibility.”
One of the main principles of geology, the science of the earth, is that the forces of nature operate (with the exception of the occasional catastrophe) in a uniform manner, i.e., that the forces operating today are the same as the ones that have done so throughout earth’s history. Therefore, the landscape we see about us is mostly the result of the accumulated effects of small increments of change over time. A bit of rock falls off a cliff. The tiny amount of acid in rainwater eats away at the rock. Raindrops act as miniature bombs that blast small craters in soil, loosening bits to be carried away by every little rivulet to join creeks and rivers, carrying more and more and finally emptying into the oceans. And the key is the immensity of time.
James Hutton is often called the father of geology. In 1775, he presented a paper before the Royal Society in Edinburgh in which he laid out the following scenario: The everlasting hills would one day be gone, their elements being redistributed bit by tiny bit into other strata. Eventually, such deposits might be uplifted by forces deep within the earth to create hills and mountains once again. Looking into the earth’s crust, Hutton concluded that the present is the key to the past; the same processes at work now have been ceaselessly at work over long ages. “I find no vestige of a beginning and no prospect of an end,” he said. The time scale involved in the mechanisms of the earth is so vast as to be beyond all our imaginings.
Stand on the rim of the Grand Canyon and look down into that deep chasm and you are gazing at formations laid down as much as a billion years ago. John Wesley Powell, in 1869 the first one to float the Colorado River down the length of the Canyon, saw therein the angled roots of mountains that have been completely eroded away and then overlain by thousands of feet of horizontal strata. He came to see that mountains cannot long remain mountains but that they are ephemeral topographic forms, saying, “Geologically, all existing mountains are recent; the ancient mountains are gone.” The mile-deep strata in the Canyon with its shells in the limestone from ancient seas, basalt from volcanic flows ages ago, and the roots of those once mighty ranges all displace us from the center stage of earth’s history.
That is part of the explanation, I think, for all the contorted efforts of the so-called creationist movement to shoehorn all of geologic time into a mere 6,000–10,000 years. Deep time—460,000 times the larger number—hugely reduces the proportion of the play for our own scene to be enacted, and hubris cannot accept that consequence.
However, much has been going on without us. The philosopher Immanuel Kant wrote, as far back as 1775 (clearly groping for words with which to give expression to the scope of the vast processes of nature beginning to be explored in his time), “Millions and whole mountain ranges of millions of centuries will pass, within which forever new worlds will be formed.” The poets, also, expressed what science found, as did Walt Whitman: “Long and long has the grass been growing. Long and long has the rain been falling. Long and long has the globe been rolling ‘round.”
How can we begin to comprehend how the earth uses time? Radiometric dating of meteors, the oldest known rocks, gives an estimate of the age of the solar system at 4.6 billion years. By way of illustration, if a year is represented by a postcard, the age of the earth would be a string of such cards placed from New York City to New Orleans, on edge. Or, one could represent the 4.6 billion years with a line fifteen miles long. In that scheme, the last six thousand years from ancient Mesopotamia to the present, which brackets what we usually call “civilization,” would be represented by just the last single inch. In vertical scale, if the history of the earth were represented by a cliff a mile high, then all of historic time occupies just the uppermost tenth of an inch, and a single lifetime occupies less than the thickness of the finest hair.
Comparisons can be made with a one-year calendar. There are many variations on this theme, in which the earth’s beginning some 4.6 billion years ago becomes January 1. Life in the sea begins about the first day of spring, March 21. It takes until Thanksgiving for aquatic creatures to begin to pioneer the land. The dinosaurs do not come on stage until December 13. They endure for more than 150 million years and, on this scale, disappear the day after Christmas. It is not until the late evening of December 31, on New Year’s Eve, that our human ancestors, the first hominids, appear in Africa. Near the very end of the last minute of the year, the Roman Empire rises and falls and, at a mere 3.5 seconds to midnight, Columbus lands in the New World.
With that type of long, long lens through which to view time, we can begin to understand how the earth has changed over the ages. Thus, the Atlantic Ocean has not always existed. Rather, the continental plates including Europe and North America have been separating and still are moving apart at the rate of approximately an inch a year—approximately the growth rate of our fingernails—but over 200 million years, the Atlantic Ocean has been formed.
We tend to think of the landscape as fixed, yet it is changing constantly. Near the farm where I grew up in the Midwest, there was a car-sized granite boulder alongside the road. Several fine fractures existed in the rock, trapping small pockets of windblown soil, and in one of them, on the spine of the huge rock, a small sapling took root. Year after year, our family noticed the tree send its roots deeper and deeper into the crevices. Rain and melting snow drained into the cracks to freeze and become icy wedges and chisels to chip away at the granite. Now the sapling is fully a tree and its irresistible growth is prying the massive rock into smaller and smaller pieces, beginning a process by which the boulder will eventually be reduced to the soil around it.
Erosion over a wide area of a landscape is too gradual to be noticed, but every rain carries immense volumes of silt and sand to the sea. In some places, the erosion is more graphic. The excavating power of the Colorado River in the Grand Canyon has been almost beyond description. Several dams have slowed the flow, but accurate records exist from the time before the dams were built, and they show an average load of silt of some 500,000 tons was being moved every day. However, in full flood, the river carried per day an estimated 55 million tons of silt, gravel, cobblestones, and boulders past the gauging station. Comparisons fail for such colossal earth moving, but consider this: