Perched On Life’S Edge

A grieving writer finds comfort atop a limestone layer that remembers both the Great Dying and life’s blind persistence

The Kaibab limestone on the Mogollon Rim is made mostly of the squished and mineralized remains of sea sponges that drifted to the floor of a shallow sea between 240 million and 260 million years ago.

The Kaibab limestone on the Mogollon Rim is made mostly of the squished and mineralized remains of sea sponges that drifted to the floor of a shallow sea between 240 million and 260 million years ago. Photo by Pete Aleshire. |

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I go to the Rim when I need to recalibrate.

So I stand now once more on this edge. The wind blows keen, prying into the seams of my clothes, whispering of vanished worlds and unexpected death.

I feel frail and mortal, swaying atop this 1,200-foot-tall cliff of limestone and sandstone, with its deep secrets. Far beyond that 100-mile view, my brother, Brian — the playmate of my youth — lies gravely ill, tethered to an oxygen tank, his heart valve stubbornly resisting the flow of his life’s blood. He is too ill at this moment even for the surgery that might save him. Once he and I lived in a created world of superheroes and secret words, shielded from grown-up eyes. But in the end, we had to enter that weighted world and forgot the secret words and the knack of finishing one another’s thoughts. We wandered away — one from the other — on unexpected trails we never planned to trod. We never topped a ridge with a view to reveal how far we’d strayed. Now as I look across the distance with death in the hollows of the hills, I am helpless and afraid.

In such times, I come to the Rim to seek a different sense of time.

I stand here in the cold wind on a slab of sea bottom limestone that bears mute witness to the brave, futile struggle of life.

Looking down along the chain of cliffs, I pick out the 300-foot-thick layer of cream-colored Kaibab limestone, made mostly of the squished and mineralized remains of sea sponges that drifted to the floor of a shallow sea between 240 million and 260 million years ago, during perhaps the most terrifying and mysterious period in life’s long history on the planet.

Some 252 million years ago, the world ended for most living things.

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At that geologic moment, the most convulsive mass extinction in the known fossil record wiped out 96 percent of all ocean-dwelling species and 70 percent of all the land-dwellers.

No one knows what happened.

Life for billions of years had flourished and diversified. The ancestors of bacteria and algae emerged mysteriously from the oceans 3.5 billion years ago and proceeded to remodel the planet. Their offspring filled the atmosphere with the oxygen necessary for the advances to follow. The first cells that could move around emerged 1.8 billion years ago, the first plants colonized the land 450 million years ago and the first vertebrates developed 525 million years ago.

By the time the Kaibab limestone started to form, life had evolved into a riot of forms. The jostling of the earth’s tectonic plates had gathered all the continents of the world had gathered into a single land mass. Shelled creatures like mollusks, squids, ammonoids and trilobites dominated the oceans. Towering, fern-like trees formed forests across the vast lowlands. Giant cockroaches scuttled through the shrubbery, dragonflies with 28-inch wingspans buzzed and hovered. On the land dwelled huge dimetrodons sporting enormous, spiny sails on their backs and in their voracious shadow scuttled the tiny ancestors of the still humble dinosaurs and creatures that would one day give rise to mammals. The plants made oxygen, the animals breathed out carbon dioxide and the world seemed safe and snug and secure — life’s nursery.

Then something happened.

In a geologic eye blink, this vast world of living things died in a cataclysm unmatched before or since. Scientists have labored for decades to understand the “Great Dying.”

The search for an explanation has uncovered a host of potential causes — and revealed the delicacy of the conditions that sustain life on this planet.

Leading theories have focused on two unimaginable surges in volcanic activity, which covered nearly a million square miles with lava. Traces remain in the form of the Siberian Traps as a result of eruptions that lasted for millions of years.

A growing body of research suggests this volcanic cataclysm might have triggered a series of other events, which multiplied the wrenching changes in the planet’s balance of heat and light. Perhaps 20 percent of the ash and rock ended up in the atmosphere, first blocking out the sun — then filling the skies with heat-trapping carbon dioxide that caused a surge in temperatures. The volcanoes alone would have doubled the carbon dioxide content of the atmosphere, causing an estimated 8-degree rise in global temperatures — similar to the project effects of human pollutants.

But the eruptions could have triggered a cascade of changes.

For instance, some research suggests the volcanoes set fire to massive coal beds, releasing 3 trillion tons of carbon into the atmosphere.

In addition, the lava flowing into the ocean along a vast continental shelf would have caused other destabilizing changes. For instance, methane clathrates form along continental margins when water molecules imprison methane molecules, which then lie buried in the mud of the seafloor. The rush of lava could have released vast quantities of stockpiled methane — a much more effective heat-trapping gas than carbon dioxide. A sharp shift in key ratios of carbon isotopes hints at such a catastrophe.

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The cliffs on the Mogollon Rim represent 300 million years of death and rebirth and the stubborn persistence of life.

Other evidence suggests that something caused the suffocating depletion of oxygen in large areas of the ocean, perhaps another side effect of the volcanic activity on the chemistry of the atmosphere.

In the end, the volcanic outpouring probably toppled a lethal line of ecological dominoes that changed the temperature and chemistry of the air and oceans.

In the end, the battered survivors persisted, although it took 15 million to 30 million years for life to make a painfully slow comeback. The dinosaurs emerged into the altered world — and had their day in the sunlight. And when an asteroid or another volcanic outpouring did them in, our warm-blooded ancestors emerged from the chaos for their turn.

All that triumph and disaster lies coded in the layered limestone before me, shrouded with ife. We all cling to that edge, to our lives, roots, tree trunks, quivering aspen, mottled lichen of ancient lineage and a grieving writer, with the blood whispering in his ears.

I wish that Brian could stand with me again on that cliff edge, to feel the wind, to yearn toward that distance, to study the layers of life and oblivion in the seams of the limestone. I pray it.

But I know now that life is so frail, such a flicker of flame.

I remember so clearly the games we played, only a little bit ago. Now we stand here on this edge, leaning into the wind, chilled to the bone.

Even so, I find some unspeakable comfort on this cliff edge, studying the Kaibab limestone and the Coconino sandstone and the hermit shale and the Supai sandstone. The cliff remembers 300 million years of death and rebirth and the stubborn persistence of life — neatly stacked.

In all the vast, shuffling, roaring, crawling crowd of species who have risen up and fallen down and passed so irretrievably away, only we have imagined extinction. But still we have gone on with the living, listening to the rush of blood in our ears.

We alone can see it coming.

And continue, nonetheless.

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