Inland sea (geology)

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An inland sea (also known as an epeiric sea) is a shallow sea that covers central areas of continents during periods of high sea level that result in marine transgressions. In modern times, continents stand high, eustatic sea levels are low, and there are few inland seas, none larger than the Caspian Sea. Modern examples might also include the recently (less than 10,000 years ago) reflooded Persian Gulf, and the South China Sea that presently covers the Sunda Shelf.[1]


This 1830 map of Australia depicts a 'Great River' and a 'Supposed Sea' that both proved nonexistent.

At various times in the geologic past, inland seas have been greater in extent and more common than at present.

  • A vast inland sea, the Western Interior Seaway, extended from the Gulf of Mexico deep into present-day Canada during the Cretaceous.
  • At the same time, much of the low plains of modern-day northern France and northern Germany were inundated by an inland sea, where the chalk was deposited that gave the Cretaceous Period its name.
  • The Amazon, originally emptying into the Pacific, as South America rifted from Africa, found its exit blocked by the rise of the Andes about 15 million years ago. A great inland sea developed, at times draining north through what is now Venezuela before finding its present eastward outlet into the South Atlantic. Gradually this inland sea became a vast freshwater lake and wetlands where sediment flattened its profiles and the marine inhabitants adapted to life in freshwater. Over 20 species of stingray, most closely related to those found in the Pacific Ocean, can be found today in the freshwaters of the Amazon, which is also home to a freshwater dolphin. In 2005 fossilized remains of a giant crocodilian, estimated to have been 46 ft (14m) in length, were discovered in the northern rainforest of Amazonian Peru.[2]
  • In Australia the promise of an inland sea is often said to have been one of the prime motives of inland exploration during the 1820s and 1830s. Although this theory was championed by the explorer Charles Sturt, it enjoyed little support among the other explorers, most of whom were more inclined to believe in the existence of a Great River which discharged into the ocean in the north-west corner of the continent.[3]
  • Also in Australia, the Eromanga Sea existed during the Cretaceous Period. It covered large swaths of the eastern half of the continent.
  • The Baltic Sea is a brackish inland sea, arguably the largest body of brackish water in the world (other possibilities include the White Sea).[4] It occupies a basin formed by glacial erosion.

See also[edit]


  1. ^ The Lord Howe Rise that covers much of the sunken "continent" of Zealandia and the largely submerged Mascarene Plateau that includes the Granitic Group islands of the Seychelles could not be considered "inland"
  2. ^ "Peru finds giant crocodile fossil in Amazon". Daily Times. September 12, 2005. 
  3. ^ Cathcart, Michael (2009). The Water Dreamers: How Water and Silence Shaped Australia. Melbourne: Text Publishing. chapter 7. ISBN 9781921520648. 
  4. ^ Baltic Sea Portal

External links[edit]

Geology Project - Inland Sea Movement Through Time