Talk:Archean

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Image: Archean landscape

@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]

I'm an instinctive critic. While I could question the value of an "artistic depiction", it may, in general, have some use. Unfortunately, I suspect that this one fails the test of being approximately right. I have the following issues: 1. My main complaint is that the atmosphere was methane rich and not likely to be "blue sky". In fact, there's another artist's depiction in this same article showing Earth from space as having a pink atmosphere! 2. The scene doesn't seem like a typical landscape. Why is the ...ocean?...depicted as being shallow and wave-less? 3. The background volcano: why? 4. The mountainsides in the background suggest they're tree covered. 5. Speaking of background, with all the "action" being in the ocean, why is most of the picture of land? 6. And yeah, achronological moon. I suggest the skies were probably too opaque to see the moon, certainly not in the detail depicted. (Not to mention so close to an active volcano.) Combine all this and there's one almost certain conclusion: that this scene is too unrealistic to be included here. Sorry to rain on the parade. There's innumerable photographs of lifeless terrain which could easily have their skies made a hazy orange-pink. FWIW. There's also innumerable photographs of the moon behind fog or clouds which could be used as a template for what an Archean sky could look like.98.17.181.251 (talk) 03:07, 12 July 2024 (UTC)[reply]

Recent 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

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

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]

It's customary in the 2020's to state "there is evidence of X" to mean "there is clear, unambiguous evidence" or "there is clear indirect evidence" or "there is some data which may be evidence". It should be apparent that there's a vast difference between these meanings. The evidence for life existing on Earth before 4 Gya isn't unambiguous. It may be biogenic, but abiogenic processes have also been suggested as alternatives. The evidence for life existing 3.7 Gya is clear and unambiguous. (keep in mind, only the scientific illiterate believe there's such a thing as "settled science"...although admittedly there is some science that is certain beyond a reasonable doubt.)98.17.181.251 (talk) 02:46, 12 July 2024 (UTC)[reply]

reflist

References

^ 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.
^ 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.
^ 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

3.26 Ga impactor's effects: a 'giant fertilizer bomb'

Paper: https://www.pnas.org/doi/full/10.1073/pnas.2408721121 "Effect of a giant meteorite impact on Paleoarchean surface environments and life" https://doi.org/10.1073/pnas.240872112 Press account @Reuters: https://www.reuters.com/science/ancient-meteorite-was-giant-fertilizer-bomb-life-earth-2024-10-21/ Interesting study. This was an impactor ~50 to 200× larger than the famous K-Pg impactor. The meteorite was a type called a carbonaceous chondrite that is rich in carbon and also contains phosphorus. Its diameter was approximately 23-36 miles (37-58 km). "Imagine these impacts to be giant fertilizer bombs," senior author Drabon said.

I'll be adding a para based on these two accounts soon. Pete Tillman (talk) 22:35, 23 October 2024 (UTC)[reply]

[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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