Sorry for the late review, turns out it's more difficult to understand geological reports than I thought. Jo-Jo Eumerus, pinging, since I have completed the review and put it on hold for the time being. I might have missed some things so I'll go over it again but for the most part there are some prose issues to be resolved from my understanding. Tayi ArajakateTalk18:45, 22 October 2020 (UTC)[reply]
Jo-Jo Eumerus, I think the article by now meets the criterion of a good article so I'll pass it, especially since there doesn't seem to be any other "former lakes" among good articles. The prose is a lot better now but I have a bit of reservation on this, for example it could have been expanded a lot more from the sources that are present here, in terms of geology, geological history as well as research history. Tayi ArajakateTalk08:31, 24 October 2020 (UTC)[reply]
The word "highstand" may be confusing for those unfamiliar with geology as a subject, I'd suggest adding a dating or period for the highstand in the lead itself to make it more clear.
The following lines, "The lake was a high altitude lake in southern Colorado. It reached an elevation of 2,335 meters (7,661 ft) at highstand and covered most of the San Luis Valley/San Luis Basin north of the San Luis Hills. Westwards, Lake Alamosa reached to the San Juan Mountains close to Monte Vista to the west. Northwards, it almost reached the present-day location of Saguache." could be phrased better.
I could suggest one, for example in the following form, "The lake was a high altitutde lake in southern Colorado covering most of San Luis Valley. It reached an elevation of 2,335 meters (7,661 ft) at highstand and spread across the San Luis Basin till the north of San Luis Hills. In the west, Lake Alamosa spread towards the San Juan Mountains and close to Monte Vista. While in the north, it almost reached the present-day location of Saguache."Tayi ArajakateTalk17:47, 23 October 2020 (UTC)[reply]
The following line, "The lake would have been nourished by glacial meltwater coming from the San Juan, Sawatch, and Sangre de Cristo Mountains." should use "was" instead of "would have been".
Couldn't the section just be merged with "Overflow" which could be renamed "Overflow and aftermath"? The last paragraph under "Overflow" does describe a bit of the aftermath. Tayi ArajakateTalk17:30, 23 October 2020 (UTC)[reply]
The following lines, "Jacob Fowler first described the existence of the former lake in 1811–1812. Decades before the region was settled and earlier than other geologic expeditions such as these of John Wesley Powell, he recorded the following:" read awkwardly and can create confusion between the two people. It should also use "those" instead of "these".
How about something akin to the following, "Decades before the region was settled and earlier than geologic expeditions such as those of John Wesley Powell, in a 1811–1812 hunting and trapping expedition, Jacob Fowler had recorded the following:" ? Tayi ArajakateTalk17:28, 23 October 2020 (UTC)[reply]
The following lines, "In 1910 proof of the existence of the lake was found in well logs. The lake is named after the Alamosa Formation, which in turn received its name from Siebenthal 1910 who in that year postulated the existence of a former lake in the Alamosa Basin." read awkwardly as well, also shouldn't it be "named by Siebenthal"? There also needs to be comma after "In 1910" and there shouldn't be a need to mention the year twice.
In that case, I'd suggest reframing it to something like the following, "The lake is named after the Alamosa Formation, which in turn was designated its name in the paper Siebenthal 1910; Claude Siebenthal had postulated the existence of the former lake in the Alamosa Basin. The proof of the existence of the lake was found in well logs in the same year."Tayi ArajakateTalk17:20, 23 October 2020 (UTC)[reply]
The following line, "Later, the geologist Ferdinand Vandeveer Hayden in 1875 wrote a more detailed account of the former lake, although he got some details wrong." is left a bit vague and can be elaborated on a bit since some examples are given in the cited source. The line should also come before the preceding line.
Pass
Neutral