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RE: mass extinctions and technology




At 03:19 PM 30/09/2002 -0400, you wrote:
> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Mark Harvey
>
> You have got to start somewhere.  To my knowledge, the organic
> environmental geochemistry of  extinction boundary sediments has
> never been
> examined.

Not so: organic (carbon isotope and other) geochemisty has been examined for
at least the K/T, and to a lesser degree some of the other events.

Not from an environmental perspective ie. PCB cogeners, DDT and it's metabolites or phthalates




> You are forgetting the dimension of time.  We may be abundant and
> widespread, but for how long?   One of the explanations given for SETI
> (search for extraterrestrial intelligence) NOT receiving any alien
> broadcasts is that civilizations capable of  radio technology
> don't last long.

While this would be true for the radio record (Fermi's paradox does indeed
neglect the time component) this would not necessarily hold for the
geological record.  We would not have to recover ALL the places humans
occupied (or dropped their trash), just a couple, in order to recognize they
we were here.

Paradigm changes generally do not occur overnight. A couple of anomalies in the fossil record are more likely to be ignored than be considered a breakthrough. Science generally demands results reproduced many times, by many different scientists before the results gain acceptance. It stands to reason that the longer we are around, the more evidence we will leave. Granted, if the soft sediments adjacent to a densely populated area were to produce some distinctive techno-fossils, and the techno fossils had hard parts amenable to mineralization, and the sediment encasing these fossils were subsequently eroded away or other wise disturbed at a time and place convenient for their discovery by a the right individual....


So many factors. How do you estimate the likelihood of fossilization of any macroscopic object existing at the earths surface for a given interval of time - natural or manmade. Such an estimate might be a good start to any discussion of the probability of us being discovered and recognized as 20th century level civilization:

For example, you might start by counting up the proportion of fossils from given area that lived in a given 1000 year period. Knowing the age of a fossil is a problem, and I suspect even this level of time resolution is not available. Maybe not even 10,000 years. This is probably what Walter Alvarez was trying to get a handle on.

If you could do this, then you might be able to say "we have recovered 0.000001 of the total tree stumps that existed in our swamp between 65,000,000 MYA and 64,010,000 MYA . You might argue that you could recover a similar proportion of plastic bottles from a swamp, over the same period, had they ever existed.

I don't think this kind of estimation has ever been attempted. So we can probably argue all day the probability of us being recognized 60,000,000 years from now. The truth is we don't even have an estimate. It may be more productive just to look for globally ubiquitous pollution tracers.


> >We have engaged in largescale transformation of the surface of the earth:
> >the foundations of shopping malls, airports, strip mines, etc. are some
> >rather large and distinctive trace fossils!!  (Particularly the
> latter, as
> >they actually enter the rock rather than merely unconsolidated
> sediment or
> >soil).
>
> Shopping malls and airports are relics of the last 100 years.
> This gives
> them a very short window of opportunity for preservation.  How
> much of the
> pyramids will remain in even another 10,000 years?

Quite a bit of the basal stones, and a lot of the quarries.


Ok, but I could have said 100,000 years still have orders of magnitude to play with.

 (In fact, the
primary evidence that would remain would, as in archaeology, be primarily
the unintended stuff: trash dumps, strip mines, houses and cars buried by
floods of the Mississippi or Hawaiian lava flows, etc.)

Also, what they lack in history shopping malls and the like make up for in
number, thereby increasing their chance of recoverability.

Professor Webster from PSU writes to me in regard to what we would leave after 65 MY:


"After 65 million years little or nothing is my guess, although a few artifacts of very imperishable materials (e.g. gold) would survive. One might be able to detect some big patterns in the ecosystem. For example, the microenvironments established over huge, human-modified urban centers such as New York might be very distinctive, but it might not be apparent why. Certain kinds of cultural contamination (particularly nuclear) would persist, and might be interpreted as human-related. But remember that 65 million years is an extremely long time. Continental drift and geomorphological restructuring would create a world that was very different from today's, thereby destroying, burying, or reducing to gibberish the archaeological record. "




> >We have been responsible for mass extinctions, but also for the
> large scale
> >homogenization of the terrestrial (and to a lesser degree
> aquatic) biota of
> >the Earth; useful and pest species are conciously (or unconciously)
> >transported by us across the planet.
>
> This homogenization could be obscured by an associated mass extinction /
> climate change = sea level instability.

However, we don't have to resort to the theoretical here. We a) have a
terrestrial fossil record and b) see no evidence at present there IS
taxonomic homogenization save for the Pangaean Late Triassic (and even here
there is regionalization).  Both terrestrial and marine paleobiogeography
are topics of some interest, and the expected results of a presence of a PHC
have yet to manifest themselves.

I concede I would expect see taxonomic some homogenization. Perhaps the "introduced species" went extinct before they had a good window of opportunity for preservation (say <1000 years). Perhaps those "introduced species" that did survive are not well represented in the fossil record. In any case, lack of evidence does not always constitute evidence of a lack. I would consider lack of industrial tracers in the geochemical record better evidence of a lack.



> >All these factors will make our presence exceedingly preservable.
>
> I think limited visible (> 1mm) evidence of our civilization may survive,
> but a combination of factors might render the evidence hidden,
> unrecognizable, or simply unrecognized.  ie. scarcity, burial, erosion,
> metamorphosis or confusion with contemporary trash.

I would argue against most of these.
Scarcity. This can always be used as an ad hoc defense for PHCs.  However,
given our current sample and given some theoretical basis (of an organism
capable of transforming some substantial part of the biomass to its own use)
we would expect that a PHC would easily be capable of population increases
in the exponential mode, as we have done.

Burial, erosion, metamorphism. If we are talking about PHCs evolving in the
later Phanerozoic (say the mid-Paleozoic onward) then the only remains that
would be lost to metamorphism would be through deep burial or those on (at
the time) continental margins, which have since been turned into mountain
ranges by collisions or lost through subductions.  Nevertheless, we still
have substantial records of parts of the Earth throughtout this interval.

Confusion with contemporary trash. This would be unlikely when you crack
open a Permian shale and find the trash therein! Remember that other
materials with similar preservability to garbage (i.e., animal parts,
leaves, twigs, pollen & spores, etc.) are routinely recovered from ancient
sedimentary rocks.  If they weren't, there would be no science of
paleontology!

Sorry to include a third parties argument, but I want to demonstrate some of the professionals are on my side. After all, the thought of a PHC does seem a bit radical:


David Fortsch from the Idaho State University writes to me:


"Let's consider the question from the preservation potential. What evidences of our having been here are most likely to survive? At various places around over the globe are what should appear to a sapient being at some future date accumulations of materials which would be out of 'normal/natural' context. These, of course, would be the remains of our urban centers. Over 65 millions of years vast amounts of change would have occurred, but 'abnormal' concentrations of admixed iron (mainly, but other metals as well), rocks of various types, some still possessing a sort of geometric arrangement might be found. It is axiomatic that preservation -- fossilisation, if you will -- requires whatever is being preserved be interred in some sort of protective medium which would exclude the natural processes of destruction --- weathering and erosion. Thus, quick burial. [Point of interest: There are striations on relatively soft rocks exposed near the southern end of the African Continent, striations resulting from glacier-related processes which occurred during pre-Cambrian time over 540 million years ago. The environment in which they occur is relatively stable, of course. Having said that, consider that the rocks at the top of Mount Everest were marine bottom sediments 65 million years ago. This makes it clear that you must put continental drift into your equation. Those current metropolitan centers on the leading edges/active margins of the continental plates would almost surely be destroyed; those on the passive margins/trailing edges would have a MUCH better chance of surviving, at least in part, as would those occupying intra-plate locations so long as these latter were not at too great elevations (severity of weathering/erosion increases with elevation and exposure to the elements). Too, consider our cemetaries. In these places we have already interred the remains of our species --- removed them from immediate destruction due to weathering and erosion. This is, at best (or worst), only temporary. If, due to geologic processes, these remains are further buried and percolating groundwaters move through to petrify or permineralise the remains, a fair number might survive. [But whether they might be subsequently discovered by a sapient being.... .] So yes, there is a chance, but not an especially good one, that remains of our civilisation and of our selves might be preserved and (even less good) subsequently discovered. "

More of my correspondence with scientists on this topic can be viewed at www.geocities.com/manpaleo/resources.html


> >The only
> >way that I envision our presence not being recoverable in the 10s-100s of
> >millions of years time scale would be if, for some reason, all Holocene
> >sediments and surfaces were somehow removed from sampling.  This
> seems very
> >unlikely.
>
>
> It would certainly by recoverable, but you would have to be
> looking for the
> right tracers in the right environment.

> Good point, but maybe such disruption has been metamorphosed.  Also, I do
> not know the estimated depletion of  earths late Paleozoic coal
> deposits.  If  we have only scratched the surface of these deposits, then
> this would reduce the chance of the same deposit being mined twice.

Actually, there are pretty good estimates for their distribution, abundance,
and resource size (as you can imagine, there are many vested interests in
getting this information!).  True, some of these resources were obviously
lost during erosion of the Appalachians and other regions.  Nevertheless,
there do not appear to be big erosional surfaces that one would expect if a
coal-based technology utilized substantial portions of this limited
resource.

I wonder what the estimates are? Also for oil, natural gas, copper, iron etc. It would be nice to know the range of ages, geographical distribution and reserves of these resources. I would be encouraged to see that most of our oil is too young to have been available in the late cretaceous. Something to investigate.



> I totally agree with you .  It takes an impact scenario these days to get
> the public interested in mass extinction (see the first five minutes of
> "Armageddon" where Bruce Willis clubs golf balls at the Greenpeace
> protesters from his oil platform).  Try to tell someone that the earth is
> warming by .5 celcius every 10 years and they will yawn and turn up the
> sport on the television.

Indeed...

> No-one was invoking an impact hypothesis until the boundary sediment's
> inorganic geochemistry was checked for by Walter Alvarez.

For the K/T, no, although it had been suggested long ago for the Late
Devonian extinction.  Furthermore, the Alvarez team wasn't even
investigating the K/T extinction event, despite popular claims to the
contrary.  They were instead simply trying to find out how much time was
represented by the boundary clay, using what they hoped would be a
time-averaged stable preservable tracer.  Unfortunately, the assumption of
time-averaging was a bit skewed in this instance... :-)

> I think an alien landing is far less likely to leave globally ubiquitous
> geochemical footprint.  Having said that, NASA will probably get
> around to
> checking for these compounds on Mars before anyone bothers to check
> earth.  I think the real reason we are slow to check  these old
> sediments (
> from the perspective of organic environmental geochemistry) is that:
>
> 1.  The technology has only been around to do so for 20 years

True.

> 2.  We think we are pretty special (see the dark ages when we literally
> thought the univers revolved around us)

See rather the points I suggested previously: i.e., without additional
supporting evidence one might not run the costly analyses.  That being said,
there has been a LOT of examinations of organic and inorganic material at
the K/T boundary, and some (but less so) at other boundaries.

Nothing is more costly than regret. A correlation between mass-extinction and industrial civilization might be just the warning we need to clean up our collective act.


Mark

50% of the worlds flora and fauna could be on the path to extinction
within the next 100 years - National Geographic