Tag Archives: Mississippi

Mexican Gulf oil spill may have precedent

When being faced with this disastrous pollution crisis it may be useful to step back and put it into perspective, to avoid overreacting. We don’t want the patient to die of the side effects of the medication, do we? It turns out that we might be able to learn something from a pre-historic event that was similar, or even worse, than this one.

The reports today (e.g., NYTimes) say that about 210,000 gallons of oil is leaking out per day. In more normal measurement units that equals 800 m3/day, or 0.01 m3/s. It’s a trickle, it’s not even a stream. A small river would typically have several, or several tens, of cubic meters per second in discharge. This is just 10 liters per second – but it is oil, not water, so it is 10 liters too much.

Where does it go? Because of its density, it ends up at the water surface, impeding the interchange of gases between the atmosphere and the ocean. With time, driven by winds and currents it reaches land and pollutes one of the most important natural environments on Earth; the coast. It dirties beaches, and destroys the conditions for creatures such as turtles who depend on them. I suppose one could include tourists in “creatures.”

Petroleum is a mixture of different hydrocarbon molecules. A portion of the oil spill is likely to sink after a while, when the lighter fractions have evaporated or been decomposed. It may become buried in the sediments again, with each drop of tar covered with sand grains. Incidentally, there is a new factory in Miami that produces instruments for monitoring this accumulation of sediments, the SediMeter.

When considering the long-term effect of the oil spill, one should keep in mind that petroleum is a natural product, unlike some other compounds that man emits to the environment. In certain parts of the world petroleum slowly seeps out of the ground – or used to, until man came around and drilled into the reservoir underneath.

However, a petroleum reservoir may have been breached naturally at the end of Pleistocene, as I argued last year in a scientific article in Geografiska Annaler, “A jökulhlaup from a Laurentian captured ice shelf to the Gulf of Mexico could have caused the Bølling warming.” From the Conclusions:

“The Gulf Coast contains vast petroleum reserves. It is arguably very likely that gas and oil was released when the Mississippi Canyon was formed. This might be the source of the increased atmospheric methane concentration recorded in the Greenland ice core at the start of Bølling and Holocene.

“This chain of events may have acted in a similar way at the end of each major Laurentian glaciation, and possibly also at D/O events. Geological data suggests that it has been repeated at least eight, possibly a hundred times, all in the Pleistocene. It may play a decisive role in bringing about the sudden climate changes that are so characteristic of the Quaternary period, as well as in creating the Mississippi Fan.”

These events took place 14,600 and 11,500 years ago, and possible a first event occurred already 15,500 years ago. It is related to the end of the Ice Age; a giant flood in the Missouri and Mississippi scourged the continental shelf off the present coastline, and eroded a canyon a mile deep. The same thing has happened once or twice at the end of every ice age, 8 times the past million years. The material was then deposited as the Mississippi Sub-Marine Fan, a mile-thick accumulation of sand and mud that has accumulated in a geological instant: A million years.

When these past oil spills hypothetically occurred, the sea level was, however, much lower than the present. Still, at that time there were coral reefs near the water surface from the southern tip of Florida and far up the east coast of Florida, just like today. The oil may have been brought to these reefs by the currents, causing severe harm to them. However, unlike today the reefs will not have been given much chance to recover, because after the megaflood in the Mississippi the world sea level would have risen dramatically. A small rise was caused by the flood itself, but instability in other inland ice sheets, and sudden global climate warming, gave rise to much more sea-level rise; many meters in total each time.

The Mississippi has a fantastic geologic history, and amazingly there is still more geologic research to be done in understanding how this all came about. The thing to keep in mind here is that (with the exception of completely new chemicals) almost nothing man does hasn’t been done already by nature itself. There is always a lesson to be learned by studying geology, and the natural variability of landscape and climate on our planet.

Path of the inferred megaflood, or jökulhlaup.
Path of the inferred megaflood, or jökulhlaup.

Finally, I wish media would listen less to the sensationalists and pay more attention to the scientific fields that have taken on a topic from the ground up, like geology, and not from the vintage point of a specific hypothesis, like global warming.