Seafloor Ooze, Subduction, and Oil

When I was a young man, I thought that having my PhD meant that I was now a scientist, that the advanced academic degree was somehow the dividing line between scientist and not-scientist. If I had been a little better at history, I would have realized that some of the greatest minds in science – people like Michael Faraday and James Clerk Maxwell – did not have PhDs. What they DID have was a tendency to think about things. The following two queries came from someone I call Patrick the Plumber Scientist.

Q: I've read the seafloor  "ooze" contains a fair amount of carbon based material. When this ooze is carried along with the seafloor downward in subduction zones wouldn't the combination of heat and pressure along with the presence of water form hydrocarbons aka oil?

- Patrick D

A: You are an unusually thoughtful person to arrive at that conclusion. Not all the ooze, as you call it, actually goes down with the subducting oceanic crustal slab – some of it gets scraped off and in some cases rafted onto a continental margin. You can find some of these strange remnants on the northern California and southwestern Oregon coastal area, among many other places in the rest of the world.

At some point the carbon from the seafloor muck that DOES go down with the oceanic crust probably passes through an oil/hydrocarbon maturation phase, but at depths and circumstances where it could not be economically extracted (even if it could be located). The muck continues down even deeper with the oceanic crustal slab to depths where even greater heat and pressure subsequently break it down to even more primitive constituents. With the water and sulfur also found in these seafloor sediments, this leads to partial melting – the lighter constituents rise through the crust (like a lava-lamp), somewhere in-board of the subduction zone to form volcanic chains like the Cascades, the Kamchatka Peninsula, the Andes, the Indonesian Archipelago, etc.

The magma that actually rises is driven at least partly by CO₂ and H₂S gases that derive from that original seafloor muck and seawater. These constituents, along with the iron, manganese, and silica of the Mantle, comprise the rising magma.  As it comes closer to the surface of the Earth, the pressure decreases and the gases come out of solution (like uncapping a bottle of soda) in that rising magma to form bubbles. This has been studied in one of our laboratories in a hot-high-pressure cell. The increasing nucleation of bubbles expands the magma volume and this causes the whole mix to accelerate upward faster and faster toward the surface. There it can often reach a runaway explosion that we call a Plinian eruption (named after Pliny the Elder, who died at Herculaneum trying to rescue friends during the eruption of Mt Vesuvius). This bubble-filled magma becomes a froth exploding violently upward into the atmosphere; it cools in the air to form the ash and tephra that (along with effusive lava) form the slopes of stratocone volcanoes like Mt Fuji, Mt Hood, and Mount St Helens.

Volcanologists work hard to measure and track volcanogenic H₂S (the burnt-match smell) and CO₂ gases to get a sense of where a restive volcano is in its possibly-pending, probably-not eruption. When Mount St Helens erupted in 2004-2006, it was relatively non-violent (though you would have died if you had been inside the crater at the time). An earlier almost-eruption in 1998 never quite reached the surface. Seismologists could see the volcanic conduit below MSH "light up" with the rock-breaking activity of a magma approaching the surface, but it never broke through. In the intervening 6 years, apparently these gases largely escaped, reducing the explosive danger from the volcano when it finally did erupt on October 1, 2004. One way to know if the CO₂ is volcanogenic, or from the modern atmosphere, is to measure its isotopic makeup. Atmospheric CO₂ has ¹⁴C ("Carbon-14"), ¹³C, and ¹²C isotopes. Volcanogenic CO₂ has only Carbon-12 (¹²C), the stable isotope in it. The other two radio-isotopes have long since decayed during the millions of years passed while the carbon was deep inside the Earth. 

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When Will the World End?

I have received episodic queries asking if the world is about to end? Sometimes these correlate with apocalyptic movies being released. Sometimes they are triggered by an uneducated conspiracy theorist (an oxymoron) somewhere with nothing better to do than to look at seismic data freely available on the web. For instance, does the latest seismic activity in Yellowstone portend the end of the world? That one turned out to be an instrumentation issue not understood by the conspiracy theorist. Do the huge earthquakes off the coast of Chile and Japan mean that the End Times are approaching? We’ve all seen trailers for movies like “Volcano” (“The Coast is Toast”), and “2012”, and I have little patience with these attempts to make money.

But when will the world really end?  Or at least become unrecognizable to us, or even uninhabitable?

Current understanding of the evolution of the Sun suggests that it is about 5 billion years old and will likely continue burning for another 5 billion years. It may start fusing helium to carbon and turn blood red before then, but the time is so distant as to be irrelevant to us.

What about things heading south on somewhat shorter time scales? An article by Wolf and Toon (http://onlinelibrary.wiley.com/doi/10.1002/2013GL058376/abstract) suggests that there will first be a “moist greenhouse runaway” event, followed by the loss of all water from the surface of the Earth, followed by a runaway thermal greenhouse situation – like Venus is currently experiencing. The Sun increases its energy output by roughly 1% every 100-110 million years. In other words, it will continue growing slowly hotter on the planet Earth (see an earlier chapter on the Faint Young Sun Paradox here: http://askageologist.blogspot.com/2012/06/snowball-earth-faint-young-sun-paradox.html).

As solar output grows, the Earth’s surface temperature should steadily rise. When it does, water vapor concentrations in the lower atmosphere will increase, and this will lead to an increase in water vapor in the Stratosphere. Solar radiation there will break down water molecules, and the Solar Wind will then blow them away into space, leading eventually to a waterless surface.  This may be what happened to Mars billions of years ago, made to happen faster and earlier due to its weaker gravity. 

Some earlier research had suggested, based on computer simulations, that a “moist greenhouse runaway” process would start about 170 million years from now, and that a full thermal runaway (the “Venus Effect”) would start around 650 million years from now. However, Wolf and Toon factor in ocean-atmosphere moderating effects from those same surface waters, and calculate something more like 1.5 billion years before the onset of the “moist greenhouse runaway” event. 

Somehow I find this difficult to worry about.

What about bad things happening on shorter time scales? For instance, what is climate change really leading to? There is no shortage of either Climate Doomsday or Climate Rubbish prophets. A recent article in EOS (Transactions, American Geophysical Union, Vol. 95, No. 18, 6 May 2014, Wuebbles et al, link here: http://onlinelibrary.wiley.com/doi/10.1002/2014EO180001/abstract) provides several illuminating graphs included here for interested readers. Figure 1 shows the severity of weather in the United States on a decade-by-decade basis starting in the 1950’s. It’s hard to argue with a graph like this: climate change is clearly well underway (see the earlier chapter on Climate Change – is it real? Here: http://askageologist.blogspot.com/2013/07/climate-change-is-it-real.html).

Figure 1. Extreme weather events in the United States by decade since the 1950's (Wuebbels, et al., 2014).

Figure 2 actually lays out the consequences for climate change: what things will look like for different parts of the country for the 2070-2099 timeframe. A short summary: it all gets hotter (no surprise), and the precipitation generally increases (surprise), except for the southwest, where precipitation will decrease (no surprise). More and greater hurricanes are projected (no surprise), but the numbers of severe tornadoes and severe East Coast winter storms have not increased in six decades and may not with the increasing CO2 and methane in our atmosphere (surprise). The minimum temperature in Alaska will be between 12 and 15 degrees (Celsius) warmer – not bad for people like me who don’t like white stuff on the ground. Perhaps more surprisingly, the northern tier of the Continental United States will get warmest – by about 6-11 degrees Celsius by the end of the century. Mean precipitation will stay pretty much the same in the Southwest – but it will be 6-8 degrees Celsius hotter, leading to drier conditions even with that precipitation. This will make those Phoenix afternoons somewhat less survivable as the century develops. 

Figure 2. What we can expect, region by region, from climate change if CO2 and methane continue to be produced by fossil fuel consumption at current rates (Wuebbels et al., 2014). 

What about economic impacts? The American Breadbasket of the central and northern plains will be seriously threatened by increasing drought conditions. Perhaps we should stop wasting 10% of our corn crop for ethanol. 

What can anyone do on their own? You should consider investing in land in the Canadian Prairie Provinces – but NOT anywhere near a modern coastline. Estimates of seawater rise vary – but they are all on the positive side, and low-lying areas like the Jersey coast, Florida, and New Orleans will be the Big Losers. An attempt to rationalize flood insurance following Hurricanes Katrina and Sandy lasted just two years – then appeals to congresspersons for relief from dramatically increased flood insurance rates “won” again. The end result is that people are rebuilding low-lying areas, and the American taxpayer will be expected to bail them out at enormous expense yet again.  Hurricane by hurricane. Science deniers apparently don’t believe in gravity, either.

Ultimately, if the world was going to end in 1,000 years, how would that be different from 1,000,000 years or 1,000,000,000 years? How would you change your life?

If you’re rational, you would not worry about the End of the World too much - unless you live on the Jersey Shore, or Florida, or New Orleans. If you are both rational and responsible, you would consider replacing your gas-guzzling SUV for something that gets better mileage. If you are still bothered, go help at a Sharing House for people who cannot get enough to eat, and you’ll feel quite a bit better afterwards.  

You will have increasing opportunities for this with time.

Aquamarine

Some people may be sitting on a gold mine – literally. I’m acquainted with some once-hard-scrabble ranchers in Arizona whose lands sat atop what would eventually become a gold or copper mine. They live in large houses and drive late-model pickups now. Other people may have stumbled on a rare fossil (a woman in Montana accidentally stumbled onto what turned out to be the most complete T Rex fossil ever found), or a rock that turns out to be a gem in more ways than one. 

Q: I have an aqua marine stone, approx 15 pounds . I would like to know it's value.
- Terry M

A: If you mean "aquamarine", then there are several possibilities:
a. a pale blue or greenish gem variety of beryl,
b. an aquamarine sapphire,
c. an aquamarine topaz, or
d. an aquamarine tourmaline.

15 pounds of any of these would be worth quite a bit, depending on the grade and quality. However, in the US Geological Survey we do highly applied research in geology and geophysics (some field offices work on ecosystems and biology). We have very specific line-item assignments in this agency, assignments set by Congress, and they do not include dealing with gem stones. As a result, we have never hired a gemologist per se as far as I know. 

I wish I could provide more help, because this is fascinating to me. In Bangkok, Thailand, there is a Wat (temple) that houses something called the "Emerald Buddha" that is apparently a carved statue of rough-grade emerald. In several senses of the word, this is a priceless artifact. Your stone would not be on par with this (it's not carved or sculpted I assume), but it is still worth something - if only as a source of material that gemologists can cut/extract high-quality raw gems from.