Talk:Archean

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Viruses[edit]

"No fossil evidence has been discovered for ultramicroscopic intracellular replicators such as viruses." But didn't the genetic makeup of viruses suggest that they derive from the very earliest life forms? That virus-like creatures/entities were a middle stage between mere organic compounds and the first cellular beings? [probably not - since they are parasitic on cellular DNA they could not have arrived prior to their hosts. Books like the recent (2016)]A New History of Life have remarked this] I know there is no fossil evidence to back this up, and I'm not a biologist, but we might want to add that such things as viruses are thought to have been around throughout the Archean. Steinbach (talk) 17:06, 17 January 2016 (UTC)[reply]

Viruses by definition are entities that don't contain all the machinery necessary for replication -- they rely on their host cells to provide the machinery they lack. Thus viruses can't exist without host cells. It is possible, and perhaps likely, that there was a middle stage of complexity comparable to modern viruses, but they could not have been actual viruses: actual viruses can't exist without hosts. Looie496 (talk) 15:47, 18 January 2016 (UTC)[reply]
I know all this, but my point is: viruses are believed to have existed in the Archean, shouldn't the article mention this fact? Steinbach (talk) 17:51, 18 January 2016 (UTC)[reply]
Sure, if we can reference a reputable published source that states such a belief. Looie496 (talk) 02:25, 19 January 2016 (UTC)[reply]

Start date for Archean[edit]

Red Planet X (Hercolubus) has been editing the start date for the Archean to be 3800 Mya, both in this article and in Template:Geological history. When I reverted, and asked for a reliable source, the editor provided a toolserver URL and reverted me. The current state of the article is now self-contradictory: it states both 4000 Mya and 3800 Mya.

Toolserver is not considered a reliable source (see WP:CIRC). There is a reliable source given in the article: the International Commision on Stratigraphy lists 4000 Mya as the start, as of 2013 [1]. Is there a better reliable source for 3800 Mya? —hike395 (talk) 20:04, 12 January 2017 (UTC)[reply]

I agree with Hike. The article cites the ICS chart as its source and we must follow it both because we have cited it and because it is the definitive offical source. Dudley Miles (talk) 22:15, 12 January 2017 (UTC)[reply]
Oh! Thanks for telling me! — Preceding unsigned comment added by Red Planet X (Hercolubus) (talk • contribs) 12:01, May 2, 2017 (UTC)

Image: Archean landscape[edit]

@Triangulum: It's a nice-enough image for Earth's surface, but the Moon is depicted in a much later era. We see Aristarchus much as it appears today and Copernicus as a very young crater surrounded by fresh ejecta. We also see Procellarum, of course, as it predates Copernicus. I believe Copernicus has been dated as about 800 to 900 million years old and Procellarum at about a billion. Aristarchus, so bright because of its young age today, is considered approximately 450 million years old. In any case, Aristarchus is clearly a very young feature.

It may well be that the artist, rather than speculate on what may have occupied these parts of the lunar surface in Earth's Archean eon, played it safe by depicting the Moon with the features that we know about now. However, this means the Moon seen here is far more evolved than it was then. The near side would not yet have had all those maria.— BruceK10032 (talk) 06:58, 28 April 2017 (UTC)[reply]

Wow. I am a year late! Excuse me! I must have missed this. I'll see what I can do to make the image better and then I'll post it here for you to check if it is good. Triangulum (talk) 14:27, 14 January 2019 (UTC)[reply]
Alright, @BruceK10032: here's the image. Triangulum (talk) 14:49, 14 January 2019 (UTC)[reply]
@Triangulum: I hate to bother you after you have already made one fix to this otherwise very nice image, but there's a bigger problem. As shown, the Moon appears to be in front of some of the background clouds. --Colin Douglas Howell (talk) 05:11, 5 May 2020 (UTC)[reply]
Oh, you’re definitely not bothering me! I see the error. Funny how these obvious things can go unnoticed for so long. I will try to make it better very soon! Triangulum (talk) 00:10, 8 May 2020 (UTC)[reply]

Recent edit[edit]

Apologies for the first part which was a mis-reading on my part. However, the last sentence of the lead states (or implies) that continents only formed during the Archean, but the main text says that some experts believe that the earth cooled enough to allow the formation of continents after 500 million years, thus in the late Hadean. Dudley Miles (talk) 15:15, 15 April 2018 (UTC)[reply]

The section in the article that says continents in the first 500 million years is poorly supported, without any citations. Richard Armstrong died in 1991, so his theories may be outdated. There are different current conflicting hypotheses about the earliest continents. One hypothesis is that a continent, Ur formed about 3 Gya.[1]. Another hypothesis is that the earliest continent as Vaalbara, dating back to 3.6 Gya.[2]. However, both of these hypotheses are quite controversial, considering the lack of geological evidence.
For the lede of this article, I think it's safe to say that continents first formed in the Archean. —hike395 (talk) 17:58, 15 April 2018 (UTC)[reply]
The lead should summarise the main text. It is unsatisfactory and confusing for readers to have a lead which contradicts it. If you are expert enough to say that the first continents definitely formed in the Archean, it would be helpful to alter the main text accordingly rather than tag saying expert attention is needed. Dudley Miles (talk) 19:23, 15 April 2018 (UTC)[reply]

Confusing Sentence on Archaen Rocks[edit]

In the second paragraph on the geology of the eon, the following sentence is found: "Although a few mineral grains are known to be Hadean, the oldest rock formations exposed on the surface of the Earth are Archean or slightly older." Now, since any time "slightly older" than the Archaean is by definition part of the Hadean eon, this makes the sentence internally contradictory. I'm not sure what the author of the sentence intended. Should it be edited to remove the introductory clause about the mineral grains, or the final clause about "or slightly older"? Doug (talk) 22:37, 16 April 2018 (UTC)[reply]

Origin of Life[edit]

This article asserts that "(t)he earliest evidence for life on Earth is graphite of biogenic origin found in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland." I'm not an expert on the subject, but, to my knowledge, there is now evidence of even more ancient life, dating to 4.1 Ga during the early Hadean (as reported in Bell et al. 2015)[3]. The article should probably be updated to reflect this. Indianajoe13 (talk) 17:52, 29 March 2022 (UTC)[reply]

References

  1. ^ Rogers, J. J. W. (1996). "A history of continents in the past three billion years". Journal of Geology. 104: 91–107. Bibcode:1996JG....104...91R. doi:10.1086/629803. JSTOR 30068065.
  2. ^ Cheney, E. S. (1996). "Sequence stratigraphy and plate tectonic significance of the Transvaal succession of southern Africa and its equivalent in Western Australia". Precambrian Research. 79 (1–2): 3–24. doi:10.1016/0301-9268(95)00085-2.
  3. ^ Bell, E. A., Boehnke, P., Harrison, T. M., & Mao, W. L. (2015). Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon. Proceedings of the National Academy of Sciences of the United States of America, 112(47), 14518-14521. Retrieved from https://www.jstor.org/stable/26465850
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