The Ice Ages

[Ophiolite]

I hope these observations about the initial recognition of Ice Ages is more in line with what Rick was aiming for.



As the 18th century, the Enlightenment and the scientific revolution progressed; scholars sought an explanation for the strange boulders, or erratics, spread across northern Europe. These distinctive rocks, often igneous or metamorphic, lay atop softer, sedimentary, layers. Their probable origin could frequently be traced to outcrops hundreds of miles away. In some cases these erratics were associated with deposits of clay dozens or even hundreds of feet thick.


The popular explanation was that these were the product of Noah’s flood. John Playfair, friend and defender of James Hutton and a leader of the Scottish Enlightenment, suggested in 1802 that they were evidence for an extensive glaciation in the geologically recent past. This proposal was largely ignored until the Europeans Venetz and Charpentier revived the notion, in the 1820s, the latter adding the observation that deep gouges in rock outcrops could have been readily produced by erratics carried by the ice and in no other obvious way.



Louis Aggasiz, from an initial position of skepticism of these works, became convinced that the three elements, erratics, boulder clay and striations, demonstrated the former existence of a vast ice sheet covering most of northern Europe. Numerous other investigators in the latter half of the 19th century, in Europe and North America, studying these data and the additional evidence afforded by such features as lake varves and raised beaches, confirmed the reality of the Pleistocene glaciation and began to work out its details.

 

[RickG]

I hope these observations about the initial recognition of Ice Ages is more in line with what Rick was aiming for.

Somewhat Ophiolite, but actually my intention is to present the science of how past climates are determined. That is an educational thread, not an "I'm right you're wrong thread", as almost threads here are. I appreciate any contributions or questions you may have.

 

[Ophiolite]

Somewhat Ophiolite, but actually my intention is to present the science of how past climates are determined. That is an educational thread, not an "I'm right you're wrong thread", as almost threads here are. I appreciate any contributions or questions you may have.

Then I am slightly puzzled. My remarks address precisely how a specific set of past climate - Ice Ages - was determined. They are, I think, pure education and free of any partisanship. They can easily be built upon, by extending them in time and scope. So, I am not quite sure what you are looking for. Would you clarify please, as it is a topic I have an interest in.

 

[RickG]

Then I am slightly puzzled. My remarks address precisely how a specific set of past climate - Ice Ages - was determined. They are, I think, pure education and free of any partisanship. They can easily be built upon, by extending them in time and scope. So, I am not quite sure what you are looking for. Would you clarify please, as it is a topic I have an interest in.

Glad to see you have an interest in past climates. You might want read through posts 13 & 14 again if you haven't already. As you can see with those posts, by specifics, I mean how do we derive information about past climates.

Here's an example. Oxygen isotope ratios in oceanic planktonic foraminifera (forams), can be used to determine past sea surface temperatures (SST). How? Forams are microscipic plankton that form calcareous shells. The composition of those shells are primarily CaCO3. Of significance there is the Oxygen (O) part of the formula, or more specifically the stable isotopes of oxygen, 16-O, 17-O, and 18-O. The important ratio there is between 16-O and 18-O, in that fractionation takes place between the two due to temperature. Thus, 18-O being heavier, will fractionate out more and more as temperature decreases. So the cooler the temperature the lower the ratio of the two isotopes, and vice verse for warmer temperature. Over time these forams die and sink to the ocean floor where sedimentary layers are formed. Drill cores are taken and analyzed for the proxy indicators in core profiles.

Now, there is much much more detail to this than I have explained and this is only a scratch on the surface of what can be learned about past climates. Sea water salinity and global ice volume can also be determined through oxygen isotopes, not to mention many other useful isotopes through biological and inorganic materials yield all sorts of information.

Though dated, here is a land-mark paper describing the process. Note that they describe many problems and uncertainties that are all now hind-sight today. Of course that doesn't mean that uncertainties are no longer encountered, indeed there are, but of a different nature and magnitude.

https://courses.seas.harvard.edu/cl...and-paleotemperature/more/Urey-et-al-1951.pdf

http://climate.colorado.edu/research/CG/CraigGordon1965_Noone_small3.pdf\

 

[Ophiolite]

We are, to some extent, talking past each other. I take a considerable interest in the evolution of ideas, that is, the history of science. In that regard the now simple observations of erratics, till, scouring and geomorphology, were what allowed 19th century scientists to recognise past climates.

For me it is valuable to begin a discussion of current methods with a review of how we began, then developed, study in any particular field.

All that said, I am still a little vague on what your goal is in this. Some possibilities, by no means exhaustive, are:
1. Point out to YECs the sophistication and wealth of evidence for one aspect of current scientific theory that challenges their worldview.
2. Educate those interested on this topic.
3. Just chat about techniques with like minded people.
4. etc.

If you could pinpoint your goal I can try to make a more relevant contribution.

 

[RickG]

We are, to some extent, talking past each other. I take a considerable interest in the evolution of ideas, that is, the history of science. In that regard the now simple observations of erratics, till, scouring and geomorphology, were what allowed 19th century scientists to recognise past climates.

I agree.

For me it is valuable to begin a discussion of current methods with a review of how we began, then developed, study in any particular field.

All that said, I am still a little vague on what your goal is in this. Some possibilities, by no means exhaustive, are:
1. Point out to YECs the sophistication and wealth of evidence for one aspect of current scientific theory that challenges their worldview.
2. Educate those interested on this topic.
3. Just chat about techniques with like minded people.
4. etc.

If you could pinpoint your goal I can try to make a more relevant contribution.

Unfortunately, in debates in the CF and other forums are little more than an exchange of rebuttals. My goal is to have doubters of, that we can actually look into the past, to ask questions as to how information is obtained and verified. It is not the guess-work they insist it is. There are proxy's left behind that occur only under specific conditions through chemical reactions and physical principles.

Unfortunately, few if any here care to actually engage in an exchange of information for the purpose of gaining knowledge and learning as you can see from some of the previous post in this thread.

Perhaps with your comments and contributions we can get some meaningful interest generated.

 

[Ophiolite]

Thanks for the clarification. I think you have a worthwhile goal, though there is a likelihood we will be set up for a doubles tennis match only to find no one on the other side of the net.

While we wait to see if anyone picks up a racquet I'll ponder alternative approaches.