Editing Neva (section)

===History of the delta===
In the [[Paleozoic]], 300–400 million years ago, all the delta region was covered by a sea. Modern relief, eminences, were formed by glacial scouring. Its retreat formed the [[Littorina Sea]], the level of which was {{convert|7|to|9|m|ft|0}} higher than its successor the Baltic Sea. Then, the [[Tosna]] was flowing in the modern lower half of the Neva as today, into the Litorinal Sea. In the north of the [[Karelian Isthmus]], the sea was united by a wide strait with [[Lake Ladoga]]. The [[Mga (river)|Mga]] then flowed to the east, into Lake Ladoga, near the modern source of the Neva. Thus the Mga then was separate from the Tosna/lower-Neva basin.<ref>{{cite book|url=https://books.google.com/books?id=LElrclnl0C8C&pg=PA217|pages=217–219|title=Climate development and history of the North Atlantic realm|author=Wefer, Gerold|publisher=Springer|year=2002|isbn=3-540-43201-9|access-date=3 December 2021|archive-date=10 April 2023|archive-url=https://web.archive.org/web/20230410073933/https://books.google.com/books?id=LElrclnl0C8C&pg=PA217|url-status=live}}</ref>

Near the modern Lake Ladoga, by [[glacial rebound]] land rose faster, and an endorheic lake briefly formed. This overspilled, eventually the whole Mga valley and thus broke into the western valley (the valley of the Tosna/lower-Neva). The Ivanovo [[rapids]] of the modern Neva were created at the breakthrough. According to early books, the breakthrough may have been about 2000 BC, but according to more recent research, this happened at 1410–1250 BC, making the river rather young.<ref>{{cite journal|title=Shoreline displacement of Lake Ladoga — new data from Kilpolansaari|last1=Saarnisto |journal=Hydrobiologia|first1=Matti
|year=1996|last2=Grönlund|first2=Tuulikki|author8=Saarnisto, Matti and Grönlund, Tuulikki
|volume= 322| issue = 1–3|pages=205–215|doi= 10.1007/BF00031829|s2cid=42459564 }}</ref>

The valley is lined with glacial and post-glacial sediments and has changed little over 2,500 years.<ref name=Geogr>{{cite book|author = Darinskii, A.V.|title = География Ленинграда|trans-title = Geography of Leningrad|publisher = Lenizdat|year = 1982|pages = 12–18|url = https://books.google.com/books?id=KuRdPAAACAAJ|access-date = 3 December 2021|archive-date = 10 April 2023|archive-url = https://web.archive.org/web/20230410074002/https://books.google.com/books?id=KuRdPAAACAAJ|url-status = live}}</ref> The delta was formed at that time, technically a pseudodelta, as not from accumulation of river material but by scouring past sediments.<ref name=SPBe>St. Petersburg: Encyclopedia. – Moscow: Russian Political Encyclopedia. 2006; {{ISBN|5-8110-0107-X}}</ref>