[Phys-L] the ultimate causative agent was global temperature reduction (see Paleocene–Eocene Thermal Maximum). Re: snowball Earth

[bernard cleyet <bernard@cleyet.org>]

"The collection at that time went from the small four-toed forest-dwelling Orohippus <https://en.wikipedia.org/wiki/Orohippus> from the Eocene <https://en.wikipedia.org/wiki/Eocene> through three-toed species such as Miohippus <https://en.wikipedia.org/wiki/Miohippus> to species more like the modern horse. By looking at their teeth he could see that, as the size grew larger and the toes reduced, the teeth changed from those of a browser to those of a grazer. All such changes could be explained by a general alteration in habitat from forest to grassland.[citation needed <https://en.wikipedia.org/wiki/Wikipedia:Citation_needed>] And, it is now known, that is what did happen over large areas of North America from the Eocene to the Pleistocene <https://en.wikipedia.org/wiki/Pleistocene>: the ultimate causative agent was global temperature reduction (see Paleocene–Eocene Thermal Maximum <https://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Thermal_Maximum>). The modern account of the evolution of the horse <https://en.wikipedia.org/wiki/Evolution_of_the_horse> has many other members, and the overall appearance of the tree of descent is more like a bush than a straight line."

https://en.wikipedia.org/wiki/Thomas_Henry_Huxley <https://en.wikipedia.org/wiki/Thomas_Henry_Huxley>  



What we are doing is only slightly less rapid than asteroids, and vulcanism.  No? 


bc   



> On 2021/Apr/16, at 08:28, Brian Whatcott <betwys1@sbcglobal.net> wrote:
>
> [Phys-L] snowball Earth
> Anthony Lapinski <alapinski@pds.org>Thu, Apr 15 at 11:27 AM
>
>   - While I was discussing the Hubble Law and expansion of the universe today   
> in my astronomy class, a student (senior) asked me an unrelated question   
> about the snowball Earth idea - that the Earth's surface was completely   
> frozen in the past, much more than a typical "ice age." How could this   
> happen? Is there any strong evidence for this? Does anyone teach this idea   
> or know of good research/papers (appropriate for high school kids)?   
>
>
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> I found that the NASA piece and the Wikipedia piece were quite accessible.The latter is replete with 95 citations
> https://www.giss.nasa.gov/research/features/201508_slushball/
>
> https://en.wikipedia.org/wiki/Snowball_Earth
>
>
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