Talk:Hadean/Archive 1

Archive 1

USGS

How can it be said that the USGS doesn't recognize the Hadean when it is a term both in their Thesaurus and a search term in GEOLEX? --Bejnar 03:36, 17 January 2007 (UTC)

131.111.243.37It is the International Commission for Stratigraphy that does not recognise the Hadean; however since there are no sedimentary rocks of this age it is not really covered by them...

Azoic

I've suggested a merge of the currently-minimal Azoic Age article to here. However, I'm not sure whether it's strictly appropriate. It's my understanding that "Azoic" was used, up until the 1950's, to refer to the entire period of time now encompassed by the Hadean, Archaean, and a large part of the Proterozoic. Does someone have a definitive reference from that era (the 1950's, that is) that could be cited? Tevildo 02:56, 20 December 2006 (UTC)

There is no "Azoic" article in the 1911 EB, but there was a lot of geology science discovered/created by the 1960s. I'll see what other sources I have handy. One comes to mind and I think I know its location. (SEWilco 05:49, 20 December 2006 (UTC))

• I would suggest extreme caution in any such merger, for the very reason you state, namely the Azoic and the Hadean are not co-extensive. In fact by some definitions of the Azoic and the Hadean they don't even overlap. Originally the Cambrian was thought to be the beginning of life, and all Pre-cambrian rocks were Azoic. Since Hadean can be read as "before the earliest known rocks", you can see the problem. Now that the term Tertiary has been depreciated, it is not appropriate to confuse the current nomenclature with the previous. Just like Tertiary needs its own article, so does Azoic. It should be an article in the history of geo-science, and focus on that. The Hadean article should focus as it does on its place in the current geologic time scale. I will look in my old textbooks for a prevalent definition of the Azoic. --Bejnar 21:34, 27 December 2006 (UTC)

I have rewritten the Azoic Age article, correcting a misapprehension, and providing references. I do not think that merger is warranted. --Bejnar 22:47, 27 December 2006 (UTC)

There was a renaming of igneous rocks in 1902.[1] Might Azoic have become entangled in this? (SEWilco 07:21, 29 December 2006 (UTC))

I did find one brief mention in 1911 EB. The Geology article at the end of Part VII says "The stratified formations of the earth's crust, or geological record, are classified into five main divisions, which in their order of antiguity are as follows: (1) Archean or Pre-Cambrian, called also sometimes Azoic (lifeless) or Eozoic (dawn of life); …". So Archean seemed more common (and is used elsewhere in the article), while Azoic was less commonly used in this book. It might be a label for the start of the Paleozoic, as earlier fossils are hard to identify and thus life seemed to begin then (during much of the early 20th century). (SEWilco 08:07, 29 December 2006 (UTC))

Do read the rewrite on the Azoic Age, and check out the footnotes which will take you into books electronically on Google Book. The term Archean replaced the term Azoic, in part because of the evolution debate. The Archean was then limited at the early end by the Hadean, and the later end by the Proterozoic. Archeozoic is another old term that you will see tossed about for (part of) this same early time. (begin smile) There remains some doubt whether there was life in the early 20th century. (end smile) --Bejnar 20:55, 29 December 2006 (UTC)

OK, I think Azoic Age can stand on its own as an article now, and I'm no longer supporting the merge - the templates can be removed after the stautory two weeks unless anyone has a different opinion. Just one point - we'll need a definite source that the renaming was "because of the evolution debate". Was there really a _debate_ in 1900? I know that the relative roles of genetics and natural selection were a matter of scientific discussion, but I didn't think that the fundamentalist opposition to evolution per se started until the 1920's. Tevildo 21:10, 29 December 2006 (UTC)

Take a look at the cartoons in Punch, the British humor magazine, at the time of Huxley's defense of Darwin. --Bejnar 02:58, 16 January 2007 (UTC)

Yes, but that was in 1860. Was there a debate in _1900_? Louis Agassiz, the last serious creationist scientist, died in 1873 - the fundamentalist movement was founded in 1910. In any case, we'll need to substantiate the claim that "the evolution debate" (rather than the normal progress of the geological sciences) influenced the renaming. Tevildo 12:27, 16 January 2007 (UTC)

I see that the merge has been proposed again. I would Oppose the merge for the reasons stated above last year. Tevildo (talk) 16:13, 11 May 2008 (UTC)

intersting info someone might like to check out

anu research It is evidence for a major rethink of the Hadean era. Have fun kids The bellman 09:07, 30 November 2005 (UTC)

• Mark Harrison, and others, in the above research studied hafnium isotopes derived from lutetium radioactive decay and found indications of a continent within 100 million years of the formation of the Earth (4.25-4 Ga). A molten Earth should not have cooled that quickly, which implies a cool planetary formation.
• Harrison and Bruce Watson also studied titanium in zircons and also found an age of 4.25-4 Ga, and the implication of a water ocean, which requires rather cool temperatures and an atmosphere.[2]
• John W. Valley, and others, found zircons of age 4.4-2.5 Ga with oxygen isotopes indicating a cool Earth and liquid water.[3]
• Other planetary formation work calculates that water molecules would have escaped Earth's gravity until a radius of about 40% of the current size, and water (and other volatiles) would have been retained after that point.[4]
• The giant impact hypothesis assumes a lot of melting during the creation of the Moon, but much of the Moon may be from the impactor.[5] Also present composition does not match complete melting and it is hard to completely melt and mix huge rock masses.[6]

So it appears either the Hadean is misnamed or it happened very early in the planet's formation. (SEWilco 04:53, 22 August 2006 (UTC))

Well, the true Hades had various places, including places of gloom, floods of lava where the Furies made their best on sinners in afterlife, and cool nice places behind the river of Forgetfullness. "Hadean" is a better name than "Azoic" anyways, and easy to remember. Said: Rursus ☻ 20:44, 21 June 2008 (UTC)

What existed before.

Is there an attempt to explain what existed before the Hadean ?

At least we can work back from this period to the present but what was before the hadean ? Kendirangu 10:24, 25 May 2007 (UTC)

The point is that the Hadean is the earliest era at which it makes sense to talk about the planet Earth. Before the Hadean, there was a protoplanet that would eventually become the Earth. Before that, it was a planetesimal (or possibly a variety of different ones that together made up the protoplanet). Before that, it was a discrete ring of dust. Before that, it was an undifferentiated part of the protoplanetary disk. These phases together are probably only a few dozen million years long.

Prior to that, the Earth was part of the even more undifferentiated solar nebula, which may have lasted for a very long time until a nearby supernova caused a shock wave that sped its rotation, flattening it into a disk and jump-starting the Sun.

See History of Earth and solar nebula for details. --216.15.6.87 12:29, 19 September 2007 (UTC)

(IN THE FUTURE, ALMOST 1 YEAR LATER, A YOUNG USER (seriously, one of the youngest users here you are dealing with) SAID THIS) Here's Earth's history (That is, the part before life)

Pre-Earth

Big Bang

Virgo Supercluster formation

Milky Way formation

Solar System formation

Sun formation

Earth formation

Hadean

-Sneaky Oviraptor18 (talk) 01:19, 24 June 2008 (UTC)

S** S** S** S** (!)

(random heading)

(random heading inserted by Said: Rursus (☻) 08:29, 30 December 2008 (UTC))

What does "after they were dep" mean? -phma

According to the author(s) of the current entry: "The term Hadean seldom occurs. W. B. Harland has coined an almost synonymous term: the "Priscoan period"." I have encountered the term 'Hadean' many times, and never 'Priscoan'. An informal Google check shows 'Hadean' (23,100) being used 25 times more often than 'Priscoan' (923). Seems the author of that sentence is pushing a terminology agenda for some reason. In other words, exaggerating or outright lying.

Let's assume good intentions and not make hasty accusations. If you check this link you will find neither of those terms, rather the new term Eoarchean for the earliest era. The International Commission on Stratigraphy is changing the rules or the names. The link above is the current status of the officially accepted nomenclature. Popular searches such as Google won't return many hits for the newly proposed official version. Vsmith 23:33, 25 July 2005 (UTC)

From my experience most astrobiologists use the term "Hadean". I personally never heard of the term "Priscoan" and I do research directly applicable to the Hadean ocean (though I guess it shows a good deal of ignorance on my side). --Asmirnov 07:44, 24 February 2006 (UTC)

The link shows a timeline starting at 3600 Ma. Hadean has traditionally referred to the period of time starting at ~4500 Ma or whenever the Earth actually formed. Regardless, synonymizing 'Eoarchean' with 'Hadean' is inconsistent with the geologic charts provided on Wikipedia with the definition of Hadean and even Eoarchean itself, and the associated 'followed by' / 'preceded by' links and notes. Even if it is the 'correct' terminology the charts should be made consistent with the text before Eoarchean is defined in the text to cover the same period, unless it is clarified that this is not the same thing as a synonym (Eoarchean has 'no defined start', but in a chronology where both terms coexist Hadean would be defined to end before Eoarchean begins). I do believe from experience that the usage of Hadean is current, regardless of the wishes of any commissions.

Hadean Rocks section

I'm a little concerned by the lack of citations in the section titled Hadean Rocks. Some of the claims are fairly hotly contested topics, such as the origin of the carbon in the Isua sediments and the implication that photosynthesis is implicated. That latter one is an enormous stretch; it's anecdotal but I am familiar with the people involved in this discussion and they're very far from a consensus view on this rather extraordinary claim. Inclusion of the supposition is fine in my view, but a citation should be provided that might help clarify the evidence for the claim. Also, are the younger, Australian rocks that are mentioned the Apex chert? I think more specifics and better citation are needed here.javascript:insertTags('70.108.60.28 (talk) 13:35, 27 April 2010 (UTC)',,)

Bad link

Refrence number two (to a MAPS article) gives a content not found error. Cwmagee (talk) 05:23, 28 April 2011 (UTC)

I found a full text copy of the paper hosted at a university website and changed the url accordingly. Mikenorton (talk) 08:41, 28 April 2011 (UTC)

More details

As much as I can see, the section "Atmosphere and oceans" is almost only handling two post-Lunar-impact states: the short rock-vapor state, and a metastable hot greenhouse state. Whether the proto-Earth was before Hadean, or in the early Hadean is not clear, if I would choose by myself, it wouldn't be reasonable to define a ridiculously short eon from about 4550 Mya to the Theia-proto-Earth collision (4535 Mya?). Anyways: what happened in Hadean was about the following:

• maybe the very early phases, with a very early very heavy bombardment,
• Giga-smack (with Transbulundum Filimanjunk Extension)!! (Lunar-impact),
• 100-1000 years of silicate atmosphere, still early heavy bombardment (EHB for simplicity)
• Does anyone besides me think that the following statement in the article is WRONG: However, a fair fraction of material should have been vaporized by this impact, creating a rock vapor atmosphere around the young planet. The rock vapor would have condensed within two thousand years? Yeah, a "giga-smack" would have created a lot of heat, but enough to keep rock in gaseous form for 2000 years? I would really like to see a solid reference for that statement. I looked at the reference provided and saw nothing there backing up that statement. — Preceding unsigned comment added by PDP-Anonymous (talk • contribs) 06:03, 6 March 2012 (UTC)
• a carbon dioxide heavy atmosphere without liquid water (X years),
• a carbon dioxide heavy atmosphere with liquid water and oceans as described in article,
• cool early earth from c:a 4300 Mya to maybe 3950 Mya, a pretty low meteorite influx, worldwide oceans, a meta stable solar system with some potential shotgun trigger instability,
• late heavy bombardment (LHB), from c:a 3950 Mya to about 3800 Mya, where the previous instability is released and creating a bombardment, my private computations gives at hand that the ocean is never-ever evaporated under this episode, but that the LHB is just an era of heavy asteroid/cometoid influx, reshaping the surface of moons and Mercury, while Earth, Mars and Venus is hottened some 20-30K for a while, and in the astroblemes some vulcanism.

(the range of LHB is not that clear, the start is variously assigned to between 4100 Mya to 3950 Mya, circa, no sources... ... said: Rursus (^mbork³) 08:40, 30 September 2009 (UTC))

Furthermore: there are some theories that the kind of hot, dry, thick and stiff crust of Venus might have been the initial state also of Earths crust. At a certain state such a crust must have transformed to the generally conceived extraordinarily mobile plate tectonics of an Early global ocean. Maybe in a Geology_of_Venus#Global_Resurfacing_Event (GRE)? Such hypothetical events are some kind of hot on the surface, Venus'es hypothetical (latest?) such GRE is believed to have been 1200°C or so. Said: Rursus ☻ 21:18, 21 June 2008 (UTC)

Abiogenesis link - please restore

the abiogenesis Zn-world paragraph including collateral links has been restored please let link stand — Preceding unsigned comment added by Lankenau (talk • contribs) 09:04, 22 March 2012 (UTC)

Hadean Atmosphere?

Should there be more discussion on differences between planet Earth and other planets that led to a creation of an atmosphere sufficient to keep water vapor in and thus create oceans? After all, if all the inner planets were a molten mass, then presumably the same conditions and processes should have appeared on each inner planet. Yet clearly, Earth was of such a unique place, that only Earth--of the inner planets--ended up with sizable oceans. What was the significant difference or differences? More detailed discussion re distance from the sun, or magnetosphere, or asteroidal/comet impacts. StevenTorrey (talk) 15:13, 13 July 2012 (UTC)

Awkward intro

The introduction of this article mentions "the name "Hadean" derives from Hades, Greek for "Underworld", referring to the "hellish" conditions on Earth at the time". But where in the article does it mention the hellish conitions? The image of a volcano reads "the Hadean eon is often characterized by extreme volcanism as Earth continued to cool", but there is no content about this extreme volcanism. Since it appears to be an important subject of the Hadean, it should be in the article. It dosen't even mention how Earth formed. Volcanoguy 14:40, 27 September 2012 (UTC)

I tried to clarify what is meant by "hellish" conditions. Did it address your concerns? Cadiomals (talk) 03:07, 29 September 2012 (UTC)

That's what I thought "hellish conditions" ment. What I am saying is there is nothing in the body of the article that mentions these things per WP:Lead section. Volcanoguy 15:34, 29 September 2012 (UTC)

I realize this is an old discussion; but according to Hugh Rollinson, Early Earth Systems: A Geochemical Approach, the actual etymology is that "hadean" refers to the hidden nature of this time period, in that the lack of solid rock hides it from our examination. Unfortunately, Rollinson does not give references for this etymology. --Yaush (talk) 16:52, 6 July 2015 (UTC)

images any one

i suggest that we add pictures —Preceding unsigned comment added by Bdoom (talk • contribs) 19:13, 8 October 2009 (UTC) What about a Chesley Bonestell image of early earth? — Preceding unsigned comment added by Hydrogeology (talk • contribs) 22:29, 3 June 2016 (UTC)

What marks its end?

What event marks the end of the Hadean and the beginning of the Archaean? -- 77.189.29.100 (talk) 14:53, 23 October 2011 (UTC)

 Done - The end of the Hadean and the beginning of the Archean is a defined-value (4000 Ma). It is now mentioned in the Archean article. Source: http://www.stratigraphy.org/ICSchart/ChronostratChart2013-01.pdf --Tobias1984 (talk) 09:27, 8 June 2013 (UTC)

This page says the Hadean ends at 4,000 million years ago while the circular graphic on this page's parent page ( https://en.wikipedia.org/wiki/Eon_(geology) ) shows it ending at 3,800 million years ago - this is confusing.  :( I know nothing about geology, by the way. Paisleypants (talk) 23:59, 15 December 2013 (UTC)

Sorry, the circular graphic is outdated. Usually 4000 million years is used now. The most official version is the chart found on the page of the international commission on stratigraphy (http://stratigraphy.org/). If your interested in how these boundaries are defined you can look at some of the pictures on https://engineering.purdue.edu/Stratigraphy/gssp/index.php?parentid=all - It is interesting to see how rocks that are older than fossilized life, are really hard to partition. --Tobias1984 (talk) 09:56, 16 December 2013 (UTC)

"The Eons of Chaos and Hades" by Goldblatt et al (which we currently have as ref #5) proposed a preceding Chaotian eon, as well as a subdivision of the Hadean into eras and periods, as described in the last paragraph of our section Subdivisions. In this proposal, the Hadean ends with the end of the Late Heavy Bombardment.

The ICS has not accepted these proposed Hadean subdivisions, nor has it accepted moving the Hadean/Arachaean boundary. However, there are enthusiasts who have embraced Goldblatt et al. Some are graphic artists who design fictional worlds for video games, etc., but based on the real world. Sometimes they make really great-looking charts and graphs. Zyxwv99 (talk) 03:57, 30 October 2016 (UTC)

Start of Hadean

The article says that Hadean starts at 4bn years ago, but spends much of the time talking about "Hadean" events around 3.8bn years ago. This needs clarifying. Fig (talk) 14:35, 6 April 2013 (UTC)

Ugh... Do you mean the end of Hadean? Red Planet X ^(talk) 12:16, 27 February 2017 (UTC)

Unreasonable precision

The infobox says that the eon began 4567.17Mya. While I am not a geologist, that seems absurdly precise for any eon, let alone this one. I am at a loss to find just where that figure is inserted into the infobox, so I was not bold. Robert A.West (Talk) 06:43, 8 June 2013 (UTC)

Hi Robert. The number is hidden in the template Template:Eons_graphical_timeline which gets the number from Template:Period_start. I made a request on the talk page of the latter to change the number to 4600. Instead of using a measured value, the base of the Hadean is now a by-definition number. I think they are planning to find a geologic event that can be radiometrically dated as a base for the Hadean to replace that number. --Tobias1984 (talk) 09:23, 8 June 2013 (UTC)