February 16, 2010
100 Million Year Ago Volcanoes Cut Oxygen Supply

The natural history of the planet Earth is full of extreme events that would wipe out humans if they occurred today.

Geoengineering -- deliberate manipulation of the Earth's climate to slow or reverse global warming -- has gained a foothold in the climate change discussion. But before effective action can be taken, the Earth's natural biogeochemical cycles must be better understood.

Two Northwestern University studies, both published online recently by Nature Geoscience, contribute new -- and related -- clues as to what drove large-scale changes to the carbon cycle nearly 100 million years ago. Both research teams conclude that a massive amount of volcanic activity introduced carbon dioxide and sulfur into the atmosphere, which in turn had a significant impact on the carbon cycle, oxygen levels in the oceans and marine plants and animals.

For a planet that is 4.5 billion years old 100 million years ago is recent geological history. What I want to know: Can Earth do this level of volcanic eruption again?

The volcanic eruptions cut ocean oxygen so much that one-third of marine life died.

Both teams studied organic carbon-rich sediments from the Western Interior Seaway, an ancient seabed stretching from the Gulf of Mexico to the Arctic Ocean, to learn more about a devastating event 94.5 million years ago when oxygen levels in the oceans dropped so low that one-third of marine life died.

The authors of the first paper, titled "Volcanic triggering of a biogeochemical cascade during Oceanic Anoxic Event 2," reveal that before oxygen levels dropped so precipitously there was a massive increase in oceanic sulfate levels. Their conclusion is based on analyses of the stable isotopes of sulfur in sedimentary minerals from the central basin of the Western Interior Seaway, located in Colorado.

A sulfate spike in the oceans increased phosphorus availability (how?) and phytoplankton went wild and created massive dead zones.

The researchers theorize that a massive amount of volcanic activity caused this sulfate spike, which triggered a cascade of biogeochemical events. More sulfate led to an abundance of the nutrient phosphorous, which allowed phytoplankton populations in the oceans to multiply. The phytoplankton thrived and then died. Their decomposing bodies depleted oxygen levels in the oceans, leading to the widespread death of marine animals.

We see a similar phenomenon on a smaller (albeit still large) scale today at the mouths of major rivers. Fertilizer run-off from farms causes massive dead zones. We need to restore wetlands that can serve as cleaners of rivers and also reduce agricultural run-off.

Share |      Randall Parker, 2010 February 16 10:30 PM  Climate Biodiversity


Comments
Brett Bellmore said at February 17, 2010 3:54 AM:

Maybe we need to aerate the ocean, so that the added nutrients can simply drive higher levels of productivity, instead?

jvon said at February 17, 2010 11:29 AM:

I'm all for that idea. I think we should members of Congress out on boats each armed with a long plastic straw, and tell them to get blowing.

I believe this would also improve the operation of our government immeasurably.

Estragon said at February 17, 2010 11:34 AM:

Obviously there is an urgent need for strict regulation of volcano standards. As usual, it should begin with higher taxes and several academic study commissions.

ajacksonian said at February 17, 2010 11:43 AM:

Can the Earth still do this nasty stuff? We can't even prepare for the light stuff, and when it gets to heavy... well, yes.

Techie said at February 17, 2010 12:06 PM:

I haven't read the papers in question yet, but a dramatic increase in ocean sulfate could lead to a phosphate increase by short-circuting the Iron-Phosphorus cycle in sediments.

Basically, bacteria in sediments can utilize Iron (Fe) (amongst other things) for respiration of organic matter, releasing dissolved iron to pore waters. This iron diffuses upwards towards the sediment/water interface until it encounters dissolved oxygen, at which point it oxidizes to Fe(III), which is insoluble and falls out as amorphous Fe-OOH. This Fe-OOH is tremendously "sticky" to Phosphate compounds and traps a significant fraction of these compounds in the sediments, rather than letting them return to the water column. This additional phosphate was released by the bacteria "re-mineralizing" the organic matter.

Umm.... this is getting too long.

Well, other bacteria in the sediments use sulfate (SO4) and release sulfide (S^-2) as the by-product. The sulfide reacts with the iron to form Fe-S compounds, known as pyrites. These pyrites aren't nearly as "sticky" to phosphates, and thus the return rate of P to the water column increases. Also, these pyrites don't really cycle and represent a net "loss" of "available Fe" in the system for future organisms.

BarrySanders20 said at February 17, 2010 12:21 PM:

So, we need to restore "wetlands" to prevent to extinguishment of human life? Maybe we shouldn't allow so much fertilizer to run off into rivers, but that's quite a leap from the very interesting points in the rest of the post about extreme events and the limited knowledge of our understanding of (and implict helplessness of humans to impact) the Earth's natural biogeochemical cycles.

Achillea said at February 17, 2010 12:35 PM:

As usual, it should begin with higher taxes and several academic study commissions.

And a regular sacrifice -- of Republicans, of course -- to the volcano gods.

Dave Eaton said at February 17, 2010 12:48 PM:

A sulfate spike in the oceans increased phosphorus availability (how?)

Just perusing the literature, it looks like phosphorus is released from Fe phosphates in the presence of sulfate. The chemistry is a little complicated, but there seems to be some good literature precedent for thinking this is so.

Gabe Skee said at February 17, 2010 1:00 PM:

Hold on - I thought global warming is now understood to be an artifact of bad science and/or bad data - are we sure we want to be messing around with geo-engineering when we aren't even sure there is any warming to be worried about?

Brian said at February 17, 2010 1:09 PM:

Congress has blown to many science related issues as it is. Anyone advocating that congress consider yet another science related issue is likely blowing congress and expecting compensation for services rendered.

McElhaney said at February 17, 2010 1:15 PM:

You're comparing fertilizer runoff to massive vulcanism that wipes out over a third of marine life?
Instead you need to be explaining why the planet survived this massive tipping point without experiencing irreversible runaway warming or cooling.
What a delicate little flower this planet is, eh?

ron said at February 17, 2010 1:34 PM:

jvon said at February 17, 2010 11:29 AM:

I'm all for that idea. I think we should members of Congress out on boats each armed with a long plastic straw, and tell them to get blowing.

I believe this would also improve the operation of our government immeasurably.


Wouldn't that dangerously raise the ocean temperatures?

M. Report said at February 17, 2010 2:01 PM:

Can Earth do this level of volcanic eruption again?

Yes: Yellowstone has blown repeatedly, and new seismic mapping
shows the underlying magma channel to be bigger and badder than
previously thought.

See also Keith Laumer's "Disaster Planet" :)

jimbo said at February 17, 2010 2:16 PM:

"Obviously there is an urgent need for strict regulation of volcano standards. As usual, it should begin with higher taxes and several academic study commissions."

I'm a volkano expurt, where do I apply for federal funds?

Wrauny said at February 17, 2010 2:58 PM:

"And a regular sacrifice -- of Republicans, of course -- to the volcano gods."
Do you say "Republican" since it's hard to find a Democrat that's a virgin?

apodoca said at February 17, 2010 6:41 PM:

jvon said at February 17, 2010 11:29 AM: Brilliant comment. LMAO!!!

Kralizec said at February 18, 2010 11:10 AM:
But before effective action can be taken, the Earth's natural biogeochemical cycles must be better understood.
But it seems that the very point of the article and this post is that cycles are not the only things that have "biogeochemical" effect. We've already fought this out in politics, several hundred years ago; Machiavelli made the point that, even if regimes succeed each other in a cycle, such a cycle is frequently interrupted by a foreign power's intervention. Volcanic eruptions and other telluride catastrophes seem to stand in relation to biogeochemical cycles as foreign intervention stands in relation to a putative cycle of regimes. And I'm here to interrupt whatever process it is that has human beings continually trying to impose a cyclical understanding on an accident-laden world.
Randall Parker said at February 18, 2010 10:43 PM:

Krazilec,

Agreed about the overemphasis on cycles. I see the embrace of cycles as driven by a desire for comfort. Cycles imply predictability, certainty, and a world that operates within manageable limits. But history is full of radical departures from previous patterns. The K-T boundary comes to mind. Ditto the Deccan Flats and the Yellowstone eruptions.

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