Söderfjärden is a

polder A polder () is a low-lying tract of land that forms an artificial hydrology, hydrological entity, enclosed by embankments known as levee, dikes. The three types of polder are: # Land reclamation, Land reclaimed from a body of water, such as a ...

in Ostrobothnia, western

Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...

, 10 kilometres south of the town of

Vaasa Vaasa (; , ), formerly (1855-1917) known as Nikolaistad (; ),impact crater An impact crater is a depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...

dating back to more than 640 million years ago (

Proterozoic The Proterozoic ( ) is the third of the four geologic eons of Earth's history, spanning the time interval from 2500 to 538.8 Mya, and is the longest eon of Earth's geologic time scale. It is preceded by the Archean and followed by the Phanerozo ...

, near the end of the

Cryogenian The Cryogenian (from , meaning "cold" and , romanized: , meaning "birth") is a geologic period that lasted from . It is the second of the three periods of the Neoproterozoic era, preceded by the Tonian and followed by the Ediacaran. The Cryoge ...

). The crater's diameter is and its maximum depth is . It is filled with

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s leaving only the outer rim visible. There is also a central uplift, which is buried. After rising from the sea due to

post-glacial rebound Post-glacial rebound (also called isostatic rebound or crustal rebound) is the rise of land masses after the removal of the huge weight of ice sheets during the last glacial period, which had caused isostatic depression. Post-glacial rebound an ...

, Söderfjärden was a wetland but was later drained with help of a pump station. It is currently cultivated and is clearly visible from air as a large hexagonal field. This makes Söderfjärden unique among the other impact structures in Finland which are at least partially below sea level. The area of the basin is divided half and half between

Vaasa Vaasa (; , ), formerly (1855-1917) known as Nikolaistad (; ),Korsholm Korsholm (; ) is a municipality in Finland, located on the west coast of the country. Korsholm is situated in Ostrobothnia (administrative region), Ostrobothnia, along the Gulf of Bothnia. The population of Korsholm is approximately , while the Va ...

, with a small corner belonging to

Malax Malax (; , ) is a municipality in Finland, located on the west coast of the country. Malax is situated in Ostrobothnia, along the Gulf of Bothnia. The population of Malax is approximately , while the sub-region A subregion is a part of a large ...

References

External links

Sundom village
travel information page about Söderfjärden.

in Finnish impact structures homepage.
The homepage
of a local exhibition site, called ''Meteoria'', in Swedish, ''Meteoriihi'' in Finnish, describing the area. Ria (riihi) is a kind of

barn A barn is an agricultural building usually on farms and used for various purposes. In North America, a barn refers to structures that house livestock, including cattle and horses, as well as equipment and fodder, and often grain.Allen G ...

, where crop is dried, and the building looks like one.
Google Earth view
Impact craters of Finland Proterozoic impact craters Landforms of Ostrobothnia (administrative region) Polders {{WesternFinland-geo-stub

See also

References

External links