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: To transport such a load in one twenty-four hour day with five-ton dump trucks would require a parade of more than 11 million of them. They would pass a given point at the rate of 125 per second! Thus, in the course of some 5 million years, the immense canyon was carved.
At Niagara Falls, the ledge over which the river flows is being cut back three or four feet per year, a process that means that the gorge is advancing upstream toward Lake Erie and in 25,000 years will reach it and empty the lake. Then, the other Great Lakes, one by one, will also be drained, becoming again the mere river valleys they were in an earlier epoch.
If a single picture could be taken every 100 or 500 years and put into a film to speed up the movement of what is happening, we would see the hills change shape like so many clouds. Time’s passage means change, oceans encroaching on the land, continents moving—transformation.
The Rocky Mountains did not always exist. In many regions, they are composed of layers that were once sediments accumulating on the floor of shallow seas from 350 million to 1 billion years ago. Those silts and limes hardened into rock and were then pushed upward at the rate of only an inch or so a year. Over 70 million years, the inches would add up to miles, but the mountains are now being eroded at least as fast as they rise. Again, these are the young mountains. All the truly ancient mountains are gone; whole ranges have been eroded away several times, a raindrop and a particle at a time . . . because the earth has an abundance of time with which to work.
“A thousand ages in Thy sight are like an evening gone,” sings an old hymn that echoes the Psalms. God has plenty of time. The physicist Freeman Dyson later occupied the position once held by Einstein at Princeton’s Institute for Advanced Study. In his book Infinite in All Directions, Dyson wrote, “Mind is patient. Mind has waited for 3 billion years on this planet before composing its first string quartet.”
4 / If These Bones Could Speak
The hand of the Lord was upon me, and he brought be out by the Spirit of the Lord and set me down in the midst of the valley; it was full of bones . . . and lo, they were very dry . . . So I prophesied as I was commanded, . . . there was a noise, and behold, a rattling; and the bones came together, bone to its bone . . . and breath came into them, and they lived, and stood upon their feet, an exceedingly great host.
Ezekiel
We could not know the extent of it at first, but the valley was indeed full of bones. More than twenty years ago, my fifth grade son, Garrett, and I were hunting dinosaurs on the prairies of the Great Plains, something we did for two weeks every summer vacation. Always in July, our trips coincided with the hottest weather when temperatures usually climbed to more than 100 degrees in the shade. (That’s something of a euphemism; there was never any shade.) We usually slept in tents, and the sudden, violent, mid-night thunderstorms generated by the heat often sent us running to the pickup cab, our path lit by near-constant lightning flashes, certain that without such refuge we would be blown away. It is all part of what one does to find fossils; however, it is pretty mild when compared to the challenges that confronted the earliest dinosaur seekers, those who explored the badlands with horses and wagons and were often days from the nearest settlements.
We camped not far from a two hundred-foot cliff overlooking a small river that had cut its winding, convoluted way down through the banded sedimentary rocks from the period of time that holds the last of the dinosaurs. The river now occupies a narrow bed that is sometimes reduced to a trickle, but it was not always such a diminutive stream, for it lies within a much larger, much more ancient channel, one of the countless channels for melt-waters from the last continental glacier. Twelve thousand years ago and some distance to the north, the front of the retreating ice would have been nearly a mile thick and waters a mile wide would have swirled and churned in the broad valley just beneath us.
Now, a herd of black cattle grazes down there in the distance; somewhat apart are several bison that a rancher has added to his operation, a practice that is becoming increasingly common in the West. A few cottonwoods dot the flood plain; most of them huge and dying, since new trees are dependant for propagation upon high water, which no longer comes due to the flow being retained and controlled by irrigation dams. A golden eagle rides the thermals above, making lazy spirals in the blue sky. Coyotes howl at first and last light; otherwise, the loudest sound is that of a bumblebee moving between coneflowers, intent upon its business, oblivious to ours.
Ours has to do with still another riverbed, over five thousand times more ancient, the cross-section of which has been exposed by erosion about a third of the way down the cliff. We had found miscellaneous fragments of bone at the bottom. When that happens, one follows the pieces upward, hoping to find the source. Perched on the side of the sixty-degree slope, hacking footholds and probing with picks and knives, the horizon that had been producing the eroded bone was revealed, and it exceeded anything we could have imagined. Wherever we probed at this zone of twelve inches in thickness, there was rust-colored bone—leg bones, ribs, foot bones, ossified tendon, vertebrae, and pieces of skull! The skeletal elements were log-jammed together at a density of about thirty bones per square meter.
