It is a loosely guarded secret in astronomy: The earth should be a lifeless snowball. Our planet lies just outside the habitable zone. Despite what creationists may say about the privileged position of our world with respect to the life giving star we orbit, we're too far out, a little too distant, a bit too cool. By the rights of thermal science our oceans should be frozen solid, our air crisp and free of humidity, and life as we know it should only huddle furtively in small pockets of melt water preserved underneath tons of ice by hot thermal vents; if at all. There are two factors preventing our lovely mother earth from descending into a grim, permanent ice age with no hope of escape. One is the sun; it's slowly heating up. The other is greenhouses gases. They're no myth. They are in fact, the breath of life itself, keeping our world twenty to thirty degrees warmer than it would otherwise be. But mythology is rife with both legendary heroes and terrible monsters. And often the two are hard to tell apart.
Two-hundred and fifty-million years ago, something happened. It was serious, it was bad, and it was huge. Whatever the cause, the event wiped out 90% or more of all living species. The holocaust is known as the Great Dying AKA the Permian Extinction (I briefly reviewed the biology and paleontology of the
Late Permian here). After the dramatic success of the Impact Theory to explain the K-T Boundary, geoscientists now turned to this greatest fossil rift of all time. But the secrets of the Permian would not yield readily. The solution would be more subtle, demanding more imagination and technical vision than a relatively simple impact to account for the destruction. What caused it? According to many among the clueless, antiscientific right, the Permian biota were killed by a
myth.
In the 1960s geologists becomes aware of a region known as the Siberian Traps . This was once an enormous complex of active shield volcanos. Recorded in the Siberian Traps is a rupture in the crust the size of Texas caused by a mantle plume of unparalleled magnitude. Here, two-hundred and fifty million years ago, raw magma and hot gasses jetted into the biosphere (A smaller version smolders even now below the scenic forest of Yellowstone National Park. It's overdue and probably only a matter of time before it goes off and lays the western US to waste).
Radiometric dating confirmed the age of the traps was right smack dab in the middle of the Great Dying. A coincidence? No way! Geologists and climatologists now had their first piece of the puzzle and it was looking ugly.
Models indicated the Permian traps would have raised the planetary temperature by three to six degrees. That's quite a bit. It would wreak havoc on our modern civilization and ravage our delicate ecosystems. But it's not enough to fully explain the geological evidence for global warming which accompanied the Permian Extinction. That evidence is consistent with a world-wide increase of ten degrees or more.
Recent evidence from Greenland brought to light by Paul Wignall provided a new, high resolution window on the Late Permian. The apocryphal era was encoded in the Greenland strata, conveniently stretched out over several meters of deposits. It became clear the event took a hundred thousand years or more, and unfolded in two stages. One was the initial rise in global temperatures of 5 degrees, and could be incorporated neatly into the Shield Volcano scenario. But then the temperature shot up another five to ten degrees very quickly and huge amounts of carbon-12 were fixed into the rock suggesting a sudden injection of carbon into the air. But geoscientists were at a loss to explain how or why such an onslaught of carbon had been unleashed.
And then, it all came together in a eureka type moment in the mind of offshore drilling expert and geologist Gerry Dickens. Methane hydrate was a curious new substances found recently in the deep ocean. At high pressure and low temperature it existed as a stable cathrate looking like bands and chunks of yellowish ice threaded into the ocean formations. The strange material even supported colonies of chemosynthetic bacteria upon which a whole pocket sized ecology subsisted. Alien looking annelids, christened 'meth worms' by deep ocean researchers crawled and burrow into the methane ice. And the hydrate it turned out would convert to gas rather suddenly if the temperature rose just a few degrees, releasing methane gas rich in carbon-12.
The mystery of the Permian Extinction may have been solved by the two pronged explanation. First, greenhouses gases built as the shield volcanos in Siberia cut loose, billowing megatons of CO2 into the atmosphere producing a greenhouse effect raising the temperature five degrees world wide. The wound in the single super continent of Pangea would eventually tear the landmass apart and send pieces of it careening over the earth's surface forming the geography we see today. Over thousands of years the higher temperatures worked into the single global ocean, migrated down to the sea floor where mighty stores of methane hydrate had probably lain dormant for ages. The methane was tipped over a phase change thermal boundary, sublimated into gas, and bubbled furiously out of the ocean. It must have looked like a ridiculously large hot tub in places as whole watery regions the size of small nations furiously fizzed and whizzed with the escaping gas. The influx of carbon-12 ratcheted up the greenhouse effect another five to ten degrees. There it remained until the excess carbon was slowly leached out by rain and fixed back into the rock by geochemical action.
A ten to fifteen degree rise today would melt the polar ice caps, and together with thermal expansion, produce a marine swell sufficient to raise global sea levels by hundreds of meters. It would submerge almost half of all present day dry land, and turn latitudes as far north as Norway or Scotland, and as far south as the southern edge of Australia, into a parched arid wasteland. Regions such as the Sahara or Gobi might bake and sear under heat annually approaching 150 degrees! Driven by a massive influx of heat and moisture, super hurricanes and typhoons would rage over the planet for years at a time. This would explain both the geochemical evidence and the Great Dying. A double whammy runaway greenhouse effect triggered first by the death jags of a super continent followed by the silent yet deadly release of carbon bearing methane from the ocean bottom. The vast colonies of cyano bacteria inhabiting oceans, rivers, and lakes first faltered and then crashed, while jungles withered and died on land. The loss of so much key plant life underpinning the food chain took down the rest of the biosphere.
Sounds bad? It was bad, and it would be catastrophic not just for civilization or our species if it happened again; it would knock off most the living creatures on earth just as it did 250 million years ago. But if you think it sounds nasty so far, it could be far, far, worse. To see how much worse we only need leave the earth for a moment and look one orbit in to our nearest planetary neighbor; Venus.
Perhaps for the first few billion years after the formation of the solar system, during the tenure of terrestrial snow and sleet here locally on a proterozoic earth, lovely Venus was also a water world. But the relentless increase in solar luminosity first evaporated and then began to outright boil the alien oceans, lifting the steamy vapor to the stratosphere, where UV and the harsh solar wind would break it down to constituent hydrogen and oxygen. Deprived of lubricating water, the great dynamo of plate tectonics seized up like an engine with sand thrown in the works. The surface rock was left exposed for eons to the rising heat, unable to recycle it's carbon back into the lithosphere. Carbon, sulfur, and nitrogen, was baked out of the rock by the megaton to join the increasingly dense atmosphere. The lighter hydrogen escaped to space, the oxygen combined with sulfur and carbon freed out of the now dry rocky tableau far below, forming dense layers of carbon dioxide and clouds of sulfuric acid. A runaway greenhouse effect ensued freeing more carbon from the strata, the cyclic process fed back on itself, and the temperature climbed to hundreds of degrees while the pressure grew a hundred-fold. Meanwhile geothermal heat built up inside the planet, and with no escape or release via the great heat engine of tectonics, it finally broke through. Judging by the incidence and age of crators on Venus, the surface eventually solidified 900 million years ago.
Thus, the surface of Venus was remade into a baked vista of pyroclastic flow and now dormant volcanic mountain chains. If there was ever life in those warm Venusian seas, it's long since been incinerated. It didn't have a chance ... Venus is no myth, it's an empirically observed set of facts available to anyone who cares to look. Greenhouse gases transformed Venus into an outpost of hell.
Speculation? Perhaps, but it's speculation worth considering. Because the same fate could sterilize the earth in two billion years- or less. Our sun continues to strengthen about 10% every billion years. As helium ash accumulates in the core and that inner sphere grows in size, the higher density holds the fusing hydrogen more tightly by gravity to its surface, burning hotter, and dumping even more helium ash inward. The surface area of that spherical helium core grows by the square of the radius, exponentially increasing the quantify of hydrogen fused per second on that surface. And for all we know, our calculations might be off a bit ...
The Permian teaches us that all it might take is a tiny push from industrial waste gases, nuclear war, or a nasty spate of volcanoes, to tip us over into ecological oblivion, a rise in global temperatures which would spell the end of our civilization and possibly our species along with scores more. We could be perched precariously at that edge right now and not know it. But the real disaster could be magnitudes worse; Our fragile biosphere could be sitting close to a runaway greenhouse phase encouraged by growing solar luminosity. A nudge, natural or manmade, might just move our inevitable rendevouz with a Dantean Inferno up a couple of billion years.
There are plenty of stores of methane left down there in the frigid ocean depths. They could be freed by another modest increase in ocean temperature. And there are other sources of runaway greenhouse gases, some of which we probably don't even understand yet. Our climate could began a meteoric rise to new balmy heights, our seas could began to evaporate, our precious water could drift higher as hot vaporous steam into the atmosphere in ever greater quantities, while carbon-12 was pumped out of a bubbling seascape from concealed stores of methane ice. It happened before, it could happen again. And this time it might not stop. In the future the oxygen could be separated from the hydrogen by UV ... in a stratosphere stripped of protective ozone by CFC's. Our water products too, could combine with the excess carbon, and drive our planet right over the Venusian precipice. In that grim future, the earth and Venus would truly be twin planets again, and much, much, sooner than we think. Planetary climate is a fragile, fickle thing. Geoscience teaches us just how terribly fragile it can be.
Geology-A dry science of stone and mineral? A Gospel of sterile dirt and lifeless mud? Hardly. Geology informs us of long vanished creatures which fosters our imagination and leave us gasping, adult and child, in awe and delight at the rich history of life on earth. Earth sciences provide the critical basic resources of energy and materials upon which our entire civilization depends and this has always been the case. The first flint nodule napped into sharp flakes and hand axes, the beautiful obsidian blades crafted by skilled Mesolithic tool makers, the early bronzed aged implements of war and peace, the great infrastructure of bridges, roads, and tunnels, even the futuristic slowly ticking nuclear heat source powering distant spacecraft as they ply the avenues of empty space and beam images of far away worlds onto our home screens and books; all arise from deep within the domain of this wonderful science, for all are found in the good earth.
Geology teaches us of catastrophes past, and likely awaiting in the wings, from the perils roaming in trackless reaches of interplanetary space, to the danger hidden in our oceans, crust, and white-hot liquid mantle. From the study of the earth we learn that we are all sailors on a Hadean Sea and that our climate is precious, unique, and ephemeral. Geology is the study of the past, for the benefit of the present, and extends protection for all of humanity from a possibly unsavory future. But only if we are smart enough, only if we strain to hear the whispers from across the oceans of time, quietly spoken in the invective of science, echoing from the vestiges of stone, steel, and rock, can we benefit. Those faint murmurs are easily lost in the noise of wishful thinking and pseudoscience. Geology may not be your bag, you may not even care much for science. But you and I can and must stand political guard against the ever present forces of ignorance, political manipulation, and superstition. We owe that to ourselves, our children, and theirs.
By a quirk of shifting political fortune we liberals, reformed republicans, decent and thoughtful theists, atheists, agnostics, democrats, libetarians, scientists and teachers, stand at a cross road in history. We and we alone seem to be left holding the line against an increasingly deranged theoconservative cabal. These throwbacks would strike down hundreds of years of scientific progress, along with the most cherished democratic values of our nation, and replace it with Literalism as decreed by (Of course) themselves.
Some feel that science is not as critically important in the great scheme of things, in the political nightmare that is unfolding in the US, or in the fight against the forces of ignorance and disinformation infecting our country. I disagree only in that I feel it's all tied together. It's all part of the big picture, all part of our platform, and all under assault by the same group of theocratic gangsters: If not us, who speaks for truth? Who speaks for science?
Our species is heir to a vast fortune. Our generous benefactor is the mother earth. Our Gaia, a breathtakingly beautiful if occasionally violent matriarch. We are one and all the children of a motherworld who endows her sons and daughters lavishly with wealth and wisdom for the taking. She is rich in resources, steeped in natural history, stern yet forgiving of our youthful indiscretions. Given respect and attention she will nurture our young species through our growing pains and beyond. And if we learn her lessons well, one day, hopefully, as all mothers must, she will bid us goodbye. We will leave our terrestrial cradle and set sail for splendors as yet undreamed; to find our own ultimate destiny in the cosmos ...
My only goal here is a much more down to earth one; to buoy your aspirations and enlist your help, so that we as a species will prevail and science will continue to be our Candle in the Dark (Carl Sagan, RIP).
I would like to thank those of you who were gracious enough to lend me your time and read any one of my rambling installments on geology, science, and creationism, over the past week. For the kind words, helpful suggestions, constructive criticisms, for all the comments and recommendations, and for technical help with formatting and fact checking via SeattleLiberal and DevilsTower; I am most grateful to all.
I wrap this series with a simple quote. One I feel sums up why geology and all of science is so critically important to our species, one which says it all so well:
Those who cannot learn from history are doomed to repeat it-George Santayana
Update: Paul Rosenberg adds in comments:
This legacy of scientific discovery has always seemed to me the most amazing of all human accopmlishments, for it is, quite literally, the ability of metamorphosis. We are creatures born into a certain world, a world shaped by what is physically real, and our understanding of it. Our skin is the boundary between us and this world. And through our understanding, we are able to transform that world, that boundary, ourselves. We shed the skin we were born into, just as we shed the world we were born into. We become, with every new discovery, profoundly different creatures than we were before.
Indeed.
~DS~