Posted by: coastlinesproject | August 9, 2011

How plankton reversed global warming, then became modern oil. etrolcooled our t

Chapter One
Paleozoic Problems

Millions of years ago, our planet was in a global warming crisis. Runaway volcanoes were belching gigatons of heat-trapping carbon dioxide into the atmosphere and giant conifer forests towered over fetid swamps. The forests’ immense trees swept carbon dioxide out of the air, then died and toppled back into the swamps, where their carbon-based trunks were sequestered under thick layers of anaerobic mud. Today, peat from those Carboniferous swamps make up our modern coal. But these early forests were limited in the amount of carbon they could sequester because they grew on land that only made up less than a third of the earth’s surface.

There were also large, stone-like structures in shallow waters along the coasts of the ancient continents. These structures, called stromatolites, contained layers of bluish-green bacteria that sequestered carbon by pulling carbon dioxide out of the supersaturated seawater. The stromatolites’ bacteria then mixed the carbon with calcium to construct their stony skeletons, much like modern corals do today. But, like the forests, the stromatolites were limited in the amount of carbon they could sequester because they could only live in sunlit waters less than a few feet deep.

Over millions of years, however, the forests and stromatolites removed enough carbon dioxide to cool our planet and stop the runaway greenhouse effect, but this shifted the earth into a bone-chilling ice age. Glaciers formed and sea levels dropped, killing the stromatolites as they became stranded on dry land. Without the stromatolites to sequester carbon, the earth once again careened back into a period of global warming. Our planet remained locked in this cycle of swings from one extreme to the other for hundreds of millions of years without a mechanism to temper the drastic changes.

About 160 million years ago, something mysterious and quite wonderful happened. A tiny new creature evolved that could draw carbon dioxide out of seawater and use it to construct its intricately beautiful calcareous shells. What was truly revolutionary about this shell-forming sea creature, was that it also evolved a planktonic lifestyle. Unlike the static stromatolites that were forever tied to the shallow waters on the edge of continents, these new creatures could drift freely over the world’s oceans that made up 70 percent of our planet’s surface and almost 90 percent of its volume. That original species then evolved into today’s riotous collection of gorgeously beautiful planktonic creatures with equally beautiful names; the foraminifera, globigerina, coccolithophores and “wing-footed” pteropods.

Billions of these tiny, planktonic calcifiers grew and reproduced. They could exist anywhere in the world’s oceans but they thrived best over deep-water basins where upwelling currents bathed them in a constant supply of nutrient-rich waters that fertilized their growth.

When these plankton died their calcareous shells rained down onto the deep ocean floor. The tiny droplets of waxy oil the plankton had used in life to keep them afloat accumulated into thousand-foot-thick deposits of calcareous ooze. Over time, these deposits were buried beneath more deep layers of sediments, and they started to cook in the heat from the earth’s interior.

Since phytoplankton is so ubiquitous, you would think oil would underlie all the world’s oceans. But petroleum is volatile stuff. If the temperature remains too cool the ooze will never cook; too hot, and the ooze will boil off as natural gas and quietly dissipate. However, if the temperature stays just right, between 212 and 275 degrees Fahrenheit, for just the right amount of time, about a million years or so, the oil simmers into a golden-brown rue of sweet, low-sulfur crude.

Only relatively small pockets of oil end up heating, under just the right conditions, for just the right amounts of time, to form commercially viable quantities of petroleum. One of the areas where this happened was below the ancient seabed of the proto Gulf of Mexico.

About 165 million years ago, the Yucatan Peninsula started to rift away from the North American plate. In its wake it left a restricted basin of warm, shallow water. Seawater would occasionally slosh into this basin and evaporate, leaving behind a thick layer of salt. The salt would be buried under succeeding layers of salt so that today the entire basin of the Gulf of Mexico is underlain by a five-mile-thick foundation of salt, called the Louann Formation.

Several ancient rivers also drained the early American continent, as the Mississippi River does today. At the same time, plate tectonics drove the American plate over a hot spot of rising magma, pushing up the earth to create the Rocky Mountains, raising the continent’s interior, and finally creating the volcano that made the modern-day island of Bermuda.

About 20 million years ago, during the Miocene, the Appalachian Mountains were pushed up by plate tectonics, creating fast flowing rivers that carried pulses of sand and mud to the eastern side of the Gulf of Mexico. Immense underwater fans of sand spread out over the slippery Louann Salt Foundation to fill up the basin of the Gulf of Mexico. The mud and sand formed river deltas and offshore islands much like those off the Mississippi River today.

As the mud and sand accumulated, they became compressed and eventually turned into sandstone and shale. Below all of this was the oil that, over time, migrated up through the formations, pooling in the porous sandstone and getting trapped beneath the impermeable strata of shale.

The shale and sandstone slid slowly over the salt foundation toward the depressed center of the Gulf of Mexico. The sliding caused the sandstone to sink down through the salt to form pockets and basins of oil, much like rock salt melts into snow. At the same time, pressure from the overlying rock caused the salt to squeeze up through and around the sandstone deposits in huge towering columns and overarching domes. The salt domes helped protect the nascent oil from overheating.

This then, was origin of sweet Louisiana crude, the genie in the lamp that saved our planet from global warming hundreds of millions of years ago. Today, that genie can either power our civilization for another 50 years, or plunge us back into another crisis of runaway global warming.

Since the early 1900’s, our species has created the planet’s four largest corporations to find and release these genies from their oily lamps. The genies have been found in Pennsylvania, California, Russia, in the ancient kingdom of Persia, off the deep-sea coasts of Brazil, the North Sea, and in the Macondo oil field in the Gulf of Mexico. Now, we have to decide if we want to put those genies back in their oily little subsea bottles once again.

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