Editing Baltic Sea (section)

==Geology==
{{main|Geology of the Baltic Sea}}
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| image1 = Baltic History 7500-BC.svg
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| caption1 = [[Ancylus Lake]] around 8700 years [[Before Present|BP]]. The relic of Scandinavian Glacier in white. The rivers [[Svea älv]] (Svea river) and [[Göta älv]] formed an outlet to the [[Atlantic Ocean|Atlantic]].
| image2 = Suomi jaakauden jalkeen.png
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| caption2 = Much of modern [[Finland]] is former seabed or archipelago: illustrated are sea levels immediately after the last ice age.
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{{Evolution of the Baltic Sea}}
The Baltic Sea somewhat resembles a [[river]]bed, with two tributaries, the [[Gulf of Finland]] and [[Gulf of Bothnia]]. [[Geology|Geological]] surveys show that before the [[Pleistocene]], instead of the Baltic Sea, there was a wide plain around a great river that paleontologists call the [[Eridanos (geology)|Eridanos]]. Several Pleistocene [[glaciation|glacial]] episodes scooped out the river bed into the sea basin. By the time of the last, or [[Eemian Stage]] ([[Marine isotopic stage|MIS]]&nbsp;5e), the Eemian Sea was in place. Sometimes the Baltic Sea is considered a very large [[estuary]], with freshwater outflow from numerous rivers.<ref name="o502">{{cite journal | last1=Myrberg | first1=Kai | last2=Korpinen | first2=Samuli | last3=Uusitalo | first3=Laura | title=Physical oceanography sets the scene for the Marine Strategy Framework Directive implementation in the Baltic Sea | journal=Marine Policy | publisher=Elsevier BV | volume=107 | year=2019 | issn=0308-597X | doi=10.1016/j.marpol.2019.103591 | doi-access=free | page=103591| bibcode=2019MarPo.10703591M }}</ref>

From that time the waters underwent a geologic history summarized under the names listed below. Many of the stages are named after marine animals (e.g. the [[Littorina]] [[mollusk]]) that are clear markers of changing water temperatures and salinity.

The factors that determined the sea's characteristics were the submergence or emergence of the region due to the weight of ice and subsequent isostatic readjustment, and the connecting channels it found to the [[North Sea]]-[[Atlantic Ocean|Atlantic]], either through the straits of [[Denmark]] or at what are now the large lakes of [[Sweden]], and the [[White Sea]]-[[Arctic Sea]]. There are a number of named and dated stages in the evolution of the Baltic Sea:<ref>{{cite journal|last1=Rosentau|first1=A.|last2=Klemann|first2=V.|last3=Bennike|first3=O.|last4=Steffen|first4=H.|last5=Wehr|first5=J.|last6=Latinović|first6=M.|last7=Bagge|first7=M.|last8=Ojala|first8=A.|last9=Berglund|first9=M.|last10=Becher|first10=G.P.|last11=Schoning|first11=K.|year=2021|title=A Holocene relative sea-level database for the Baltic Sea|journal=Quaternary Science Reviews|volume =266|at=107071|doi=10.1016/j.quascirev.2021.107071|doi-access=free|bibcode=2021QSRv..26607071R }}</ref> 
* [[Eemian Sea]], about 130,000–115,000 years [[Before Present|BP]] 
* [[Baltic Ice Lake]], 16,000–11,700 years {{abbr|cal.|calibrated}} BP
* [[Yoldia Sea]], 11,700–10,700 years cal. BP
* [[Ancylus Lake]], 10,700–9,800 years cal. BP
* [[Mastogloia Sea]], 9,800–8,500 years cal. BP
* [[Littorina Sea]], 8,500–4,000 years cal. BP
* Post-Littorina Sea, 4,000–present

The land is still emerging [[isostasy|isostatically]] from its depressed state, which was caused by the weight of ice during the last glaciation. The phenomenon is known as [[post-glacial rebound]]. Consequently, the surface area and the depth of the sea are diminishing. The uplift is about eight millimeters per year on the Finnish coast of the northernmost Gulf of Bothnia. In the area, the former seabed is only gently sloping, leading to large areas of land being reclaimed in what are, geologically speaking, relatively short periods (decades and centuries).

===The "Baltic Sea anomaly"===
{{main|Baltic Sea anomaly}}
The "Baltic Sea anomaly" is a feature on an indistinct [[sonar]] image taken by Swedish salvage divers on the floor of the northern Baltic Sea in June 2011. The treasure hunters suggested the image showed an object with unusual features of seemingly extraordinary origin. Speculation published in [[Tabloid journalism|tabloid newspapers]] claimed that the object was a sunken [[UFO]]. A consensus of experts and scientists say that the image most likely shows a natural [[geological formation]].<ref name="Snopes">{{cite web|last1=Mikkelson|first1=David|title=UFO at the Bottom of the Baltic Sea? Rumor: Photograph shows a UFO discovered at the bottom of the Baltic Sea.|url=http://www.snopes.com/photos/supernatural/balticufo.asp|website=Urban Legends Reference Pages© 1995-2017 by Snopes.com|date=9 January 2015|publisher=Snopes.com|access-date=1 August 2017|archive-date=30 May 2020|archive-url=https://web.archive.org/web/20200530150111/https://www.snopes.com/fact-check/unidentified-submerged-object/|url-status=live}}</ref><ref name="HowStuffWorks">{{cite web|last1=Kershner|first1=Kate|title=What is the Baltic Sea anomaly?|url=http://science.howstuffworks.com/environmental/earth/oceanography/baltic-sea-anomaly.htm|website=How Stuff Works|date=7 April 2015|publisher=HowStuffWorks, a division of [[InfoSpace Holdings LLC.]]|access-date=1 August 2017|archive-date=12 October 2017|archive-url=https://web.archive.org/web/20171012154533/http://science.howstuffworks.com/environmental/earth/oceanography/baltic-sea-anomaly.htm|url-status=live}}</ref><ref name="LiveScience">{{cite web|last1=Wolchover|first1=Natalie|title=Mysterious' Baltic Sea Object Is a Glacial Deposit|url=https://www.livescience.com/22846-mysterious-baltic-sea-object-is-a-glacial-deposit.html|website=Live Science|date=30 August 2012|publisher=Live Science, Purch|access-date=1 August 2017|archive-date=2 August 2017|archive-url=https://web.archive.org/web/20170802043222/https://www.livescience.com/22846-mysterious-baltic-sea-object-is-a-glacial-deposit.html|url-status=live}}</ref><ref name=PopMech>{{cite journal|last=Main|first=Douglas|title=Underwater UFO? Get Real, Experts Say|journal=Popular Mechanics|date=2 January 2012|url=http://www.popularmechanics.com/technology/aviation/ufo/underwater-ufo-get-real-experts-say|access-date=14 March 2018|archive-date=28 December 2014|archive-url=https://web.archive.org/web/20141228221843/http://www.popularmechanics.com/technology/aviation/ufo/underwater-ufo-get-real-experts-say|url-status=live}}</ref><ref name=":0">Interview of Finnish planetary geomorphologist Jarmo Korteniemi (at 1:10:45) on {{Citation|last=Mars Moon Space Tv|title=Baltic Sea Anomaly. The Unsolved Mystery. Part 1-2|date=30 January 2017|url=https://www.youtube.com/watch?v=inIBLxONMBM&t=4245| archive-url=https://ghostarchive.org/varchive/youtube/20211123/inIBLxONMBM| archive-date=23 November 2021 | url-status=live|access-date=14 March 2018}}{{cbignore}}</ref>