Talk:Geologic time scale

Interpolation

This commment is copied/pasted from above, and I started a new section to discuss it: Some rock layers are accurately dateable, most are not. Using stratigraphic principles, those layers that are not dateable can be dated approximately around the correct age. This would be a good topic to cover. Hardyplants (talk) 02:26, 10 February 2009 (UTC)

I agree that this would be useful. Does anyone have a suggestion as to where this would be useful to insert? Off the top of my head, the methods used for dating units that are not directly absolutely datable are:

• Interpolation of sedimentation rates
• Correlation with units which contain material that may be absolutely dated
• Correlation of fossils present with absolutely-dated sections with the same fossils
• Cross-cutting and erosional relationships to provide upper upper or lower bounds on when the units could be deposited.

Awickert (talk) 02:56, 10 February 2009 (UTC)

Another significant contribution is the use of the climatological effects of Milankovitch cycles to date sequences either absolutely (eg in terms of years before present) or relatively (in terms of intervals). This is because the effect of long-duration cycles in the Earth's orbit - precession, obliquity and eccentricity - can be used to interpret sedimentological cycles in a manner analogous to the use of tree-rings to date wood, except that the Milankovitch cycles span many thousands of years rather than sequences of single years. This approach has made important contributions to the chronology of the Cenozoic and many other parts of the Phanerozoic (cf eg A Geologic Time Scale 2004, Gradstein et al). The use of annual and sub-annual (eg tidal) laminations in lake and some marine sequences has also made very important chronological contributions. Orbitalforam (talk) 18:48, 15 May 2011 (UTC)

Earth clock

Mapping geological time units to 24 hours is a potentially useful educational tool, however the present graphic is erroneous. Rescaling the dates presented in the article to 24 hours would have the Archean ending at 10:52 (not approx. 18:40 as indicated) and the Proterozoic much longer. The 2 ma of the Quaternary represents 37.8 seconds (not 17). Some of the other boundaries look a little off too.

I don’t have the graphics skills or software to replace the clock image so for now shall simply remove it. If anyone cares to redo the graphic I’d be quite happy to contribute a full set of calculations. Shythylacine (talk) 07:06, 7 March 2009 (UTC)

Maybe a simple way to do it would be to use the ICS chart divided by 4.567 billion years, and make a pie chart in Excel, which we could then annotate. Anybody think this is too shoddy? Awickert (talk) 07:16, 7 March 2009 (UTC)

Another suggestion I have come across recently (documentary & book) is a 365 day calendar representing the timespan of the earth. Now I am not suggesting to replace that with the 24 hour day but a nice addition if someone wants to take up the gauntlet :-) -- Phoenix (talk) 08:38, 7 March 2009 (UTC)

That sounds like a cool idea - do you know how to make a succinct graphic out of it? (The nice thing about the clock was the circle.) Awickert (talk) 08:45, 7 March 2009 (UTC)

OK, here's an Excel pie chart clock, pretty shoddy compared to the original image, but accurate. Now, where to put it? I think the original was out of place in the history section so would suggest below the graphical time-line. It wouldn't need much text, eg:

"Another method of envisioning the geological time scale is to compress its vast length to 24 hours.

Once again, at 37.8 seconds the Quaternary is too short to display on a clock face."

So, is it too shoddy? Perhaps superfluous? Shythylacine (talk) 06:54, 8 March 2009 (UTC)

I'm glad I checked Wikipedia - I was just starting to make one of my own, so I'll stop. I actually really like it - I say it should definitely go in, and is a really good graphic! Awickert (talk) 08:45, 8 March 2009 (UTC)

Thanks for the image but could you add the Hadean? I found this image and since it is made by the US government I believe we can upload it or just use it as a reference (here's another one). Maybe a clock in a clock might be a good idea? Strike all that wikipedia already has a nice one... I'll change it right now.

As for the calendar idea it was shown as a full year calendar with all the days coloured to represent the geological times. So you see all 365 days at once and the amount of time each eon/period/etc took up. -- Phoenix (talk) 09:46, 8 March 2009 (UTC)

Cool! But now I like both; the bottom one looks nicer, and the top one has all of the geological periods in 2 circles. I wonder if it would look bad to use both, or if we can get away with it. Awickert (talk) 10:25, 8 March 2009 (UTC)

Problem is you can't read the text on the lower image - even at the 600 pixel scale it's a challenge for my bleary eyes (maybe I need more coffee to clear the morning fog). Point being, do we need the second, unreadable image just 'cause it's "prettier" - seems redundant to me. Vsmith (talk) 13:03, 8 March 2009 (UTC)

Personally it showed up just fine on my PC at 600px. Well since the newly created one was re-inserted I placed the File:Geologic clock.jpg image I found on wikipedia higher since the articles title is Geologic time scale. But can anyone edit the File:Earth Clock 2.gif image to include Hadean? If not it should just show the pre-cambrian. -- Phoenix (talk) 03:04, 9 March 2009 (UTC)

I omitted the Hadean on account of its informal status, but have since seen that ICS use it (informally) on their 2008 [[1]]. So yep, agree that Hadean needs to be in. The term is such evocative counterpoint to all those -zoics too ;) Shythylacine (talk) 10:39, 9 March 2009 (UTC)

This article does not need two clocks. Of the alternatives I prefer the one with the black background for its greater information density, so shall delete mine. I also prefer its aesthetics - the round clock of earth in the black of space-time. It's not perfect, but it's not boring either. The present layout with the clock next to the introduction leaves space to add some caveats and disclaimers in an expanded caption. Will have a go at that now. Shythylacine (talk) 10:52, 9 March 2009 (UTC)

OK - but please leave it on Commons: I like it, and have some friends who teach intro geology who would find something like that useful. Awickert (talk) 00:05, 10 March 2009 (UTC)

Well if you do keep the image can you either edit or upload a version that has the Hadean in it? Either that or make it pre-cambrian :-) -- Phoenix (talk) 08:49, 10 March 2009 (UTC)

March 23, 2009 Vandalism

64.187.47.18 made a series of changes on March 23, 2009. Most were silly vandalism such as adding the everett to several random locations.

Two were more substantial. This person apparently removed the much of the "History of the Time Scale" section. This revision could not be easily undone, and restoring the section is beyond my wiki-abilities. This person also made a revision deleting several lines from the "Graphical Time Scale" section. Also could not be "undone". Could someone else fix these? —Preceding unsigned comment added by Ukemike (talk • contribs) 21:22, 25 March 2009 (UTC)

Time scale changes

I suggest that the eras in the Hadean Eon be removed. They do not reflect either the International Commission on Stratigraphy International Stratigraphic Chart 2008, the Commission for the Geological Map of the World Geologic Time Scale 2008 color coding, or USGS time scales (see below).

Also, the text states the colors are from the ICS standard, but this is not the case. They more closely resemble USGS time scale and geologic map colors.

-Parsa (talk) 02:31, 29 March 2009 (UTC)

I personally like having the Hadean subdivisions because, although not official, they are used in the literature.

The color issue has been brought up before; if there's a consensus to change the timescale templates to use the ICS colors, I'd say it would be a decent thing to do, and would help. Awickert (talk) 04:22, 29 March 2009 (UTC)

Page size

As of this posting, the page is 3.4MB in total! 59.167.39.47 (talk) 12:01, 28 April 2009 (UTC)

Help requested

In watching recent changes I came across this edit: [2]. Seeing this was a revert of a ClueBot reversion and noting a less than gentle appraisal of the redirect as it was, I reverted. The editor has taken issue with my reversion. With my limited experience in the technical details of the subject I am hesitant to take issue with the editor (even though I think the ClueBot version was correct). If the editors here could look into the matter I would appreciate it. If I'm making mountains out of mole hills, I will offer my apology in advance. Thanks. Tiderolls 15:33, 29 April 2009 (UTC)

including the terminology "age"

I was wondering in the Geologic time scale#Terminology the table of "Units in geochronology and stratigraphy" should include the classification systems of Age and The Great Year as footnotes.

In the Origin of Religion (part 2) it mentions that in the Ancient Science (Astronomy and Astrology), each 25,765 years is called The Great Year according to the 12 Celestial sphere Constellation, that is viewable from Earth. There hasn't been any new map/grid (proposals, theories, concepts...etc) published to the any research organization or to the general public and I think this infromation if perfectly valid, since current science still related information like Equinox, Solstices, Star navigation...etc. There is also scientific evidence that this time measuring system is based on the Earth's axial precession and each 2150 years is called an Age. --75.154.186.241 (talk) 22:59, 26 September 2009 (UTC)

Galactic Year

I've never seen the 'galactic year' used for purposes of geology other than on the linked page (which calls it a suggestion, not an accepted convention) and derivative Wikipedia entry. Moreover, the abbreviation "GY" is highly unfortunate as it may easily be interpreted as "gigayear" (properly "Ga"). I propose the section be deleted as non-notable. Orcoteuthis (talk) 21:30, 19 November 2009 (UTC)

Unreliable source - Muslimheritage.com material

Content from Muslimheritage.com / FSTC is an unreliable source, as discussed on Wikipedia:Reliable_sources/Noticeboard/Archive_18#History_of_Science. None of its publications are peer-reviewed, and its authors often exhibit a strong bias and incomplete or flawed citation practices. The site has been used as a source in numerous science and history of science articles to make extraordinary claims about Islamic invention and discovery. I am working to remove these extraordinary claims where they stem directly and solely from a Muslimheritage.com reference. Many of these claims were added by a user who has a history of using flawed sources for extraordinary claims, as discussed on Wikipedia:Requests_for_comment/Jagged_85. That page details numerous examples where claims from these sources contradict more reliable sources, on a scale which casts the entirety of the material originating from the site into doubt. If you would like to discuss this or any related removal with me, please leave a note on my talk page. Dialectric (talk) 12:05, 26 April 2010 (UTC)

Early Cambrian

There is a mess-up on the chart in the Early Cambrian section. The early is located in the Supereon when it shouldn't be there. I am not even going to attempt fixing it beacause I am not good at the table making stuff. Can someone fix this? Andrew Colvin | Talk 05:53, 4 June 2010 (UTC)

Misuse of sources

Jagged 85 (talk · contribs) is one of the main contributors to Wikipedia (over 67,000 edits; he's ranked 198 in the number of edits), and practically all of his edits have to do with Islamic science, technology and philosophy. This editor has persistently misused sources here over several years. This editor's contributions are always well provided with citations, but examination of these sources often reveals either a blatant misrepresentation of those sources or a selective interpretation, going beyond any reasonable interpretation of the authors' intent. Please see: Wikipedia:Requests for comment/Jagged 85. The damage is so extensive that it is undermining Wikipedia's credibility as a source. I searched the page history, and found 7 edits by Jagged 85 (for example, see this series of edits). Tobby72 (talk) 16:55, 18 June 2010 (UTC)

Children's books being used as a reference

I deleted references to the following book from this and several other articles today, on the basis that it is a children's book (aimed at 11–14 year old children, according to the publisher):

• Scheppler, Bill (2006). Al-Biruni: Master Astronomer and Muslim Scholar of the Eleventh Century. Great Muslim Philosophers and Scientists of the Middle Ages. New York: The Rosen Publishing Group. ISBN 978-1-4042-0512-3.

I do not believe that such a book can, by its very nature, be considered a reliable source; certainly such books don't seem to be considered appropriate by WP:SOURCES for example. (Note that I didn't delete the claim it was being used to support: I just replaced the reference with {{Cn}}.)
This change was reverted with the comment that "no evidence of unreliability yet adduced". As I say, I don't think that reliability or otherwise is the issue here: the book is simply unsuitable for a reference in an encyclopaedia. But as it happens, on the very page (86) being used as a reference (see Google books), we can find the claim that "Ibn Sina embraced the heliocentric theory" which is plainly false. The explanation on page 84 of that book about Biruni's reasons for placing the orbits of Mercury and Venus below that of the Sun also looks very confused to me.
If books such as this should be used as references for material such as this, could someone explain to me why, as I really don't see that it is appropriate.
Many thanks. –Syncategoremata (talk) 21:38, 18 June 2010 (UTC)

Individual Pages for Eras During the Archean Eon are Misrepresented a Eons

First off, I just wanted to note that this (the Geologic Time Scale) is truly a great addition to the ever-growing Wikipedia body of knowledge and I greatly appreciate the efforts of those involved to putting together the section.

I noticed the other day, while perusing the individual pages dedicated to the eras of the Archean Eon, that each of those eras, on their respective pages (in the colored graphics on the right side of the page), are misrepresented as eons. As I am relatively new to Wikipedia, I haven’t the ability to correct this and would offer the correction up to whomever is currently overseeing the aforemntioned pages. --Astro1001 (talk) 16:18, 5 August 2010 (UTC)

Thanks, the wrong template had been applied. I've removed Template:Geological eon as those aren't eons. Vsmith (talk) 21:43, 5 August 2010 (UTC)

Kaapvaal craton, Kalahari craton & Vaalbara

I would like to propose that these terms be inserted (with their respective links) together with the (Canadian Shield and the Pilbara Craton) under the Paleoarchean section as major events.
Furthermore would anybody be so kind and inform me as to what is required to improve the Kalahari craton page (http://en.wikipedia.org/wiki/Kalahari_craton) and the Kaapvaal craton page (http://en.wikipedia.org/wiki/Kaapvaal_craton) so as to meet Wikipedia's quality standards. Any help will be greatly appreciated.
Many thank SamiAEH (talk) 18:00, 16 August 2010 (UTC)

There is an incongruence in origin of animal phyla in the detailed scale. If there were trilobitomorphs since pre-cambrian (ediacaran according this scale), most of animal phyla were already established in that supereon, not in Cambrian. Trilobitomorphs are well-defined chelicerate, then we have to accept older origin of phyla. There were molluscan shells, already as gastropods or cephalopods, from pre-cambrian too. I would suggest anyone could take out "most modern animal phyla appear" from cambrian. One should search more about origin of phyla to write a better informatin about this... —Preceding unsigned comment added by 187.64.36.244 (talk) 15:48, 22 August 2010 (UTC)

Terminology: Late/Upper

I've tidied up the terminology section to make it a bit clearer that Upper/Lower refers to rocks and Late/Early refers to time. Hopefully I've got the intermediate right as well (middle = time, mid = rock), but that was based partly on memory and partly on the chart further down the page. Can someone less rusty confirm (or correct) this please. 62.172.108.23 (talk) 11:40, 1 September 2010 (UTC)

A comparative geological timescale

The graphic captioned "A comparative geological timescale" [File:Geological_Time_Scale.png] has some problems. The Miocene and the Holocene both are omitted from the Neogene in the fourth bar from the left (second to last bar), which is the most serious problem. Whether the fifth bar (subdivisions of the Holocene) even belongs in a graphic for this article is another question. --arkuat (talk) 06:18, 3 September 2010 (UTC)

Spiral graphic

The spiral graphic (http://en.wikipedia.org/wiki/File:Geological_time_spiral.png) is possibly outdated. According to the International Commission on Stratigraphy the Pennsylvanian and Mississippian are not periods, but epochs of the Carboniferous. It's a great graphic, though. (I also contacted the author of the original poster, via http://pubs.usgs.gov/gip/2008/58/) --Furrfu (talk) 19:15, 8 September 2011 (UTC)

Letter designations for periods etc

I wonder if we don't put somewhere within this page some reference to the letters which stand for each of the Phanerozoic periods and indeed the eras and eons of the Precambrian. I'm talking of course about N=Neogene, G=Palaeogene, K=Cretaceous, J=Jurassic, T=Triassic, P=Permian, C=Carboniferous, D=Devonian, S=Silurian, O=Ordovician, E=cambrian and X=Neoproterozoic, Y = Mesoproterozoic, Z=Palaeoproterozoic and A=Archaean. Many are straightforward enough, others may not appear so at first glance - some explanation for the lay-reader might assist. I don't know but I have always presumed that these were agreed by the ICS. Perhaps someone who is more familiar with the subject than I, might care to comment? cheers Geopersona (talk) 09:49, 12 December 2010 (UTC)

This article is in dire need of a controversy section

Kent Hovind & his ministry is an infamously unreliable source -- dismissed even by many creationists, and thus no basis for adding material to the article, and a very poor basis even for article talk discussion. WP:NOTAFORUM
The following discussion has been closed. Please do not modify it.
The stance of Creation Science Evangelism as well as CMI and many other creationist ministries is that the earth is NOT billion of years old as is seen throughout their audio-video materials available online such as this one from CSE http://www.drdino.com/seminar-part-1-the-age-of-the-earth In regards to the carbon dating bezerk stuff which is all one big huge assumption based on the CIRCULAR REASONING of the geologic tables (the fossils are dated by the layers and the layers are dated by the fossils) their stance is also the same, as in it being an utter fairy tale. Here is one source content from CSE http://www.drdino.com/questions-and-answers-seminar-part-7a Someone REALLY has to add this section to the article due to the fact that after watching these 2 videos in their entirety (the first deals with the ASSUMPTION that the earth is millions of years old based on the same ALLEGED datings by carbon dating which is covered in video number 2) one CAN NOT ascertain that the statement according to which the earth is billions of years old (As the fairy tale line says "Once upon a time") is anything buth a lie, myth and deliberate speculation. PLEASE ONLY COMMENT TO THIS POST AFTER WATCHING BOTH VIDEOS YOU CAN NOT APPROPRIATELY COMMENT IF THE CONTENT THAT IS ACCUSING THIS HAS NOT BEEN VIEWED AND UNDERSTOOD Sergiu-Daniel (talk) 18:08, 16 December 2010 (UTC)

Please don't shout. And as noted in reply to your identical rant on talk:Age of the Earth, take it to Dating creation or the religion article of your choice. This article is about the geologic timescale and its development. Vsmith (talk) 18:29, 16 December 2010 (UTC)

OK, scrap Hovend, what about CMI http://creation.com/age-of-the-earth and other creationist ministries that clearly refute the "once upon a time the earth formed" phrase and support the young earth theory. Their arguments are the same as Hovend's, the gology column is based on circular reasoning, the layers are dated by the fossiles and the fossiles are dated by the layers. Can any of you give me one bit of scientific evidence for this fairy tale of a geology column? Who came up with the numbers? The radiocarbon dating that can't properly date a NY Times paper, or anything else of known age for that matter? Here are some of CMI's arguments: Many fossil bones “dated” at many millions of years old are hardly mineralized, if at all. (http://creation.com/dinosaur-bonesjust-how-old-are-they-really) They have at least 101 arguments against your holy geology column which atheists venerate so religiously!!! "Billions of years agooooo........" Do you think that 101 arguments from only 1 website (with accredited scientific research) is enough for you guys to start a controversy cathegory on this article??????????????????????? — Preceding unsigned comment added by Sergiu-Daniel (talk • contribs) 20:49, 30 December 2010 (UTC)

How many arguments do you need me to post here before someone will start a controversy section on this article? There obviously is one between evolutionists and creationists on this very subject, why has Wikipedia fallen behind at catching up with this? Sergiu-Daniel (talk) 20:58, 30 December 2010 (UTC)

No, there is no controversy about the geological time scale. A few religious fanatics will try to claim otherwise, but this is an article about science, not about fringe religious sects. DuncanHill (talk) 21:11, 30 December 2010 (UTC)

OK. When I'll have some spare time after the holidays I'll bombard this discussion page with REAL SCIENTIFIC facts against this overrated religious geology column that is always being introduced with the oh so venerated "unce upon a time" (billions of years ago...) Sergiu-Daniel (talk) 22:28, 30 December 2010 (UTC)

<chuckles> First you'd have to find some "real scientific facts". Given that you have cited nothing but Creationist Christian apologetics here & on Talk:Age of the Earth, I consider (i) that it is unlikely that you even know where to look for them & (ii) that your claim that the "geology column" is ludicrously WP:POT. In any case controversy sections are depreciated per WP:STRUCTURE. Hrafn^Talk_Stalk(P) 03:09, 31 December 2010 (UTC)

So here is one argument that is against the geologic time scale. http://www.icr.org/article/445%20/ The Polystrate Trees and Coal Seams of Joggins Fossil Cliffs initially discovered by Sir Charles Lyell, friend and colleague of Charles Darwin. Why aren't his findings not even mentioned on this article? Petrified trees sitting upside-down throughout the hole column. This really shoots the geologic time scale between the eyes...Sergiu-Daniel (talk) 21:55, 6 January 2011 (UTC)

I believe I said "real scientific facts" -- not bogus pseudoscientific claims, made by a geological engineer not a geologist, and published by an organisation that could not even convince the state of Texas (hardly a liberal hotbed) that what they were teaching is "science education". For a scientific treatment of the topic, read Polystrate fossil, and then the sources cited there. Hrafn^Talk_Stalk(P) 04:29, 7 January 2011 (UTC)

See also Creationist Claim CC331, which links to further rebuttals. I would note that this claim is old and long-debunked. Hrafn^Talk_Stalk(P) 05:10, 7 January 2011 (UTC)

Please stop feeding the troll and holding up this soapbox. This is not the place for debunking science, there are plenty of blogs in cyberspace. It's time to close down this discussion as an abuse of a wikipedia article talk page. --Kleopatra (talk) 05:15, 7 January 2011 (UTC)

Errors in Terminology section

"If the entire history of the Earth was to be compressed into one day, ... the first life will appear at 6:00 pm"

That's about 1.5 billion years ago, yet the graphic shows that life originated on earth at least 3.8 billion years ago. I guess "life" in that section should be corrected to "multicellular life" since that appears to be what the graphic indicates. Ashwan (talk) 18:36, 8 November 2011 (UTC)

Also:

"the Moon will be forming at 5:00AM"

That would put the moon formation sometime around the end of the Archaen. The time should be more like 12:05AM. 65.102.180.83 (talk) 05:10, 5 December 2011 (UTC)

supereon: when? where? who?

The timescale chart in this article includes a unit of geological time called a "supereon". Since I have never encountered this term before, I would be interested to know more about it. For many years the term "precambrian" has been used to (informally) identify any time earlier than the cambrian (period); I guess the motivation for this was that, throughout much of the early development of geology, fossil evidence (more or less) started in the cambrian. To formalise this by creating a time unit corresponding to the precambrian is not unreasonable (since the term "precambrian" is not assigned to any other geological time unit). However, naming the following supereon the "cambrian" is unsystematic (since it duplicate the long-establised name of the cambrian period). It seems very unlikely to me that an organisation such as the International Commission on Stratigraphy would adopt such an unsystematic practice. Can anyone identify a primary source for the formal adoption, firstly, of a time unit called "supereon", and, secondly, of a supereon called the "cambrian". When was it first published? In what article or publication? By whom? FredV (talk) 19:42, 13 November 2011 (UTC)

The International Commission on Stratigraphy's guidelines explicitly permit the use of 'super-' and 'sub-' when applied to stages/ages, series/epochs and periods/systems so as to enable useful grouping and dividing though no reference appears to be made to either eras/erathems or eons/eonothem in this respect - either in support or to the contrary. See http://www.stratigraphy.org/upload/bak/chron.htm It may perhaps then be seen as a natural and convenient extension (if not officially sanctioned) of the application of the prefix 'super-' to collectively describe the Precambrian eons which alone (maybe?) in stratigraphic terms would otherwise have no following noun - so 'supereon' does perform a role. However any reference to a 'Cambrian Supereon' would simply be an error. cheers Geopersona (talk) 05:40, 22 February 2012 (UTC)

Correction needed in Table 2

In the table that lists the "Units in geochronology and stratigraphy", the number of eras is listed as 12. But from the time scale it is pretty much clear that the number is 10. I believe that when removing the eras from the Hadean eon this number went unnoticed. — Preceding unsigned comment added by 122.178.18.231 (talk) 16:51, 14 November 2011 (UTC)

Thanks, I changed it to 10 - I don't believe that there are any formally accepted subdivisions of the Hadean. Mikenorton (talk) 17:51, 14 November 2011 (UTC)

time scale condensed into a single day

Whilst I am aware this analogy gets used, I am doubtful as to its value in an encylopaedia article. It does not really add value to the extensive scientific presentation of the time scale presented above. Would we also end up comparing the Structure of the Earth to a peach? Babakathy (talk) 07:31, 6 January 2012 (UTC)

I would have to agree. Hrafn^Talk_Stalk(P) 08:06, 6 January 2012 (UTC)

So I will also have to reluctantly agree. (Rats.) I have to remember WP:NOTTEXTBOOK: "Wikipedia is an encyclopedic reference, not a textbook. The purpose of Wikipedia is to present facts, not to teach subject matter." I'm a teacher, and just naturally fall into what I do best.

On the light side, Babakathy, no, not a peach; an apple! :-) Yopienso (talk) 10:13, 6 January 2012 (UTC)

Ah yes, shows more heterogeneity than a peach...Babakathy (talk) 10:48, 6 January 2012 (UTC)

Agree with all. Not encyclopedic, its as simple as that. Cadiomals (talk) 19:04, 6 January 2012 (UTC)

Historical use of terms era and period

We ought perhaps to make reference in the article to the fact that the fourfold division of Earth history employed by early geologists made use of the term era for each of these divisions. Two (the primary and Secondary) were abandoned at an early stage but use of both Tertiary Era and Quaternary Era continued into modern times - these eras being subdivided into the Miocene Period, Eocene Period etc. Only later was the Tertiary reclassified as a period itself and its subdivisions downgraded to epochs -I am not sure exactly when that occurred but for example Britain's Institute of Geological Sciences' fourth edition of the regional guide to the geology of 'The Wealden District' of southeast England (which was published in 1965) refers to the Tertiary, the third geological era (p45) and goes on to talk about the Eocene System and so on. cheers Geopersona (talk) 05:53, 22 February 2012 (UTC)

Completely Earth-centric

Mercury also has eras. It would be nice to list other planets/bodies that have a time scale. Solar Apex (talk) 08:25, 23 April 2012 (UTC)

It also would be nice to create a comparative time scale for planets. Solar Apex (talk) 08:27, 23 April 2012 (UTC)

I have absolutely no idea what this is talking about! The Geologic Time Scale to which the main article refers is a human construct, developed to organise the observed structure of the geological record. Since Geology is study of the structure of the Earth, it is no surprise that the timescale only refers to the Earth. What does it mean to say "Mercury (or the Moon, or Rigel) have eras or have a time scale"? If it just means they have existed for a long time, then most of the objects in the universe have eras. If it means that a study of their structure would reveal recognisable stages of change with time, this is very likely true, but until such a study is undertaken, there will be no defined time scale; I am not aware of any observation-based time scale for any astronomical body other than the Earth (we simply don't have the millions of stratigraphic observations required to establish such a time scale). FredV (talk) 12:43, 23 April 2012 (UTC)

We know comparatively little about the geological histories of other planets and moons within our solar system but it seems that we do know enough to have established geological time scales for some of them eg Mercury, Mars and our own Moon. These might be considered provisional divisions of the timescales just as we have been able to refine the timescale for the evolution of the Earth. Now, the lunar and Martian subdivisions are styled 'periods' whereas the timespans which they occupy equate broadly with terrestrial eons. I can see that there may indeed be merit in laying out, side by side, these timescales and those of other nearby bodies with a view to making comparisons - after all there are elements of shared history amongst the members of our solar system family - the early and late heavy bombardments come to mind. This article is not the place to do so however. cheers Geopersona (talk) 19:16, 23 April 2012 (UTC)

Just to clarify my point. The term "geologic time scale" applies not only to the Earth even though "Geos" in Greek means Earth (See Lunar geologic timescale as an example). So I would expect this to be an article that talks about what geologic time scale is in general with references to geologic time scales for some bodies, the Earth included. For example, most of the contents of this article could be transferred to something like "Geologic time scale of the Earth". Or even better, just rename this article to "Geologic time scale of the Earth", and have another article about general stuff. Certainly, there is a value of laying timescales side-by-side, but on a separate page. Solar Apex (talk) 21:49, 23 April 2012 (UTC)