Monday, April 29, 2013

Re: [Geology2] Naming "Deep Time" was The Earth Moved



The majority of these boundaries are marked by an extinction event as I recall from my geology class a couple of years ago...


On Mon, Apr 29, 2013 at 8:50 AM, Lin Kerns <linkerns@gmail.com> wrote:
 

I don't recall an extinction event between the Triassic and the Jurassic. Also, between the Carboniferous and the Devonian. I remember something about how man designates the end of some periods by the change in stratigraphy. Am I thinking right on this?

Lin


On Sun, Apr 28, 2013 at 8:37 PM, MEM <mstreman53@yahoo.com> wrote:
 

It shouldn't be so counter-intuitative but we are kind of stuck in a circular argument.  Extinction events were what made us take notice of the changes in lifeforms. ( Not all extinction events gave rise to an ages or period designation)  They didn't fully comprehend it at the time but, "extinction followed by radiation" was what early geologist were taking mental note of when assigning names to time segments. It isn't that "bad stuff" happened at the end of these man named time periods but, we named the ends when we found the "bad stuff".

Geological-time designation is an artifact of man not nature.  Extinction events are how we designate the end of all units of geological time.  I can think of only one which is not extinction related: Eudicarian. This was not an extinction but a radiation where life started leaving "fossil-lizable" soft structures.  Ok-- one more-- the "onset" of the Cambrian when life again left a different kind of body structure: "hard body", which could be preserved.

Eman

From: Kim Noyes <kimnoyes@gmail.com>
To: Geology2 <geology2@yahoogroups.com>
Sent: Sunday, April 28, 2013 7:07 PM
Subject: Re: [Geology2] Re: The Earth Moved

 
In some cases those, too. However, foremost on our minds is the End Cretaceous Event and the Cretaceous is a period. I suppose we could expand my comment to include "most eras, epochs, periods, etc. Bad shit seems to mark the boundary of one of these time frames.


On Sun, Apr 28, 2013 at 2:38 PM, Lin Kerns <linkerns@gmail.com> wrote:
 
Kim, don't you mean eras?



On Sun, Apr 28, 2013 at 3:56 PM, Kim Noyes <kimnoyes@gmail.com> wrote:
 
For the most part all the geologic periods in Earth's history are separated from one another by catastrophes of global proportions.


On Sun, Apr 28, 2013 at 1:44 PM, Clay Chesney <fossrme@yahoo.com> wrote:
 
Very good article by Richard Conniff. It points out how rigid and resistant to change the scientific community can be. As a general rule, I follow the advice of the philosopher Bertrand Russell, who said it is alright to disagree with the experts when they are strongly divided, but it isn't wise to do so when the great majority agree on an issue. In this case, however, the great majority was wrong, and we don't have to look far to find other examples.
 
 In 1980 when Luis and Walter Alvarez proposed that the extinction of the dinosaurs at the end of the Cretaceous was caused by the catastrophic impact of a large meteorite their hypothesis was met with a firestorm of ridicule from geologists. This reaction came, in large part, because of a conflict between religion and the fledgling science of geology in the 1800s. The religious establishment saw the earth as having been shaped by cataclysms induced by God's wrath, while the geologists countered with the principle of uniformitarianism which emphasized the influence of slow natural processes of the kind we see acting around us every day. As a counterweight to religion and superstition, uniformitarianism became so entrenched in the basic wisdom of geology, that claims of catastrophic events were immediately rejected. This was something I heard many times as a geology student. When the Alvarezes announced their meteorite theory, with all its attendant media attention, geologists rushed forward, hotly proclaiming that the story was like something from the pulp magazines at the check out counter. It took a number of years before the accumulated evidence was persuasive enough to win over the geological establishment, which is still not entirely convinced. Extremely rare events, especially highly destructive ones, were just not a part of the normal criteria for evaluating the world, even among a group that studied eons of earth history. The resistance to Wegner's continental drift theory wasn't based only on the lack of a reasonable explanation of how continents might move across the earth's surface; it depended equally on how tenaciously we all cling to apparently logical decisions, amplified and reinforced by a community of peers and backed by the authority of established institutions.





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