The Seas Could Turn
to Sulfur
By Peter D. Ward
Peter Ward has been
active in Paleontology, Biology, and more recently, Astrobiology for more
than 40 years. Since his Ph.D. in 1976, Ward has published more than
140 scientific papers dealing with paleontological, zoological, and
astronomical topics.
He is an
acknowledged world expert on mass extinctions and the role of
extraterrestrial impacts on Earth. Ward was the Principal Investigator of
the University of Washington node of the NASA Astrobiology Institute from
2001-2006, and in that capacity led a team of over 40 scientists and
students. His career was profiled by the Pulitzer Prize winning reporter
William Dietrich in The Seattle Times article "Prophet, Populist, Poet of Science."
His books include
the best-selling "Rare Earth: Why Complex Life Is Uncommon in the
Universe" (co-author Donald Brownlee, 2000), "Under a Green Sky:
Global Warming, the Mass Extinctions of the Past, and What They Can Tell Us
About Our Future" (2007), and "The Medea Hypothesis: Is Life on Earth
Ultimately Self-Destructive?" (2009).
TRANSCRIPT
Question: What
non-greenhouse extinction events have happened in the past, and are they likely
to recur?
Peter Ward: Well, we
certainly know that we were hit 65 million years ago by a very large rock from
space, Hollywood knows this with the two blockbusters, “Armageddon” and “Deep
Impact,” so it must be true. It was really interesting, in ’95, Spielberg sent
his minions to a conference to where a number of us were attending about this
particular hit and indeed, there is a great danger out there. We are surrounded
by asteroids, some become berth crossing. Jupiter has a way of perturbing
comets and sending them from stable orbits to earth-crossing orbits. We will
get hit again. How big the hit will be is only a matter of time until we get
something the same size that killed off the dinosaurs, should humanity last
long enough that is. But that size hit looks like only once every 100 million
years, or more. We haven’t had a hit that size for the last 500 million years.
So, it does look like it is a rare event to have something that big; a 10
kilometer asteroid hit us.
Question: Given
the low number of extinction events in recent Earth history, are we “due” for
another?
Peter Ward: Well,
no, it’s just the whole sense of when is it going to happen again and it
appears that most of the big mass extinctions have been caused by these nasty
volcanic events. The last one didn’t cause a mass extinction. It was in the
Tertiary Period. This was in my own home state, Washington State, the Columbia
River Basalts. Out came all this basalt, as liquid lava, and a lot of the carbon
dioxide came out too, but not enough to cause the earth to go into a really
nasty mass extinction. The mass extinctions caused by the basalts again, are
simply by heating the world. Now when you heat the world you heat the pole more
than you do the equatorial region. When that happens, you start losing
circulation. The only reason you have wind now is you have a hot spot and a
cold spot and they’re trying to equilibrate. Well, an ocean current you have
the same thing. You have a cold Antarctic and then you warm them up, the ocean
circulation system is dampened down; there’s much less heat difference.
So when we heated
the poles to the point that there is no longer – or already in a very sluggish
ocean circulation, the ocean is going oxic, they lose their oxygen. They only
keep oxygenated now because of this vigorous mixing. Well, even when you have
oxygen in the atmosphere and contact with the surface, once you slow down any
circulation, that whole basin can lose this oxygen. The Black Sea is the same
case. It’s sits under a 21% oxygen atmosphere, and yet the Black Sea, except
for the top several meters, in anoxic. It’s black because it’s producing a lot
of sulfur-producing bacteria and there’s very nasty gasses that are produced.
We now think the
big mass extinctions were caused by global anoxia. The oceans themselves so
sluggish that the hydrogen sulfide bacteria are produced in huge areas of the
ocean bottom bubbles up to the surface and starts killing things; rotten egg
killing. It would be extremely nasty. Hydrogen Sulfide poisoning is a horrible
death. Two hundred hydrogen sulfide molecules among a million air molecules is
enough to kill a human. I mean, just breathing in 200 of those little things
amid all the million you’re got in oxygen and boom, you’re down, horribly down.
So, this is a
really nasty poison and it was certainly present in past oceans during these
short-term global warming events. That’s why it’s really spooky what we’re
doing now.
