Söderfjärden is a
polder
A polder () is a low-lying tract of land that forms an artificial hydrological entity, enclosed by embankments known as dikes. The three types of polder are:
# Land reclaimed from a body of water, such as a lake or the seabed
# Flood plains s ...
in
Ostrobothnia, western
Finland, 10 kilometres south of the town of
Vaasa. The plain is in an
impact crater which was made at least some 640 million years old (
Proterozoic
The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided ...
, near the end of the
Cryogenian
The Cryogenian (from grc, κρύος, krýos, meaning "cold" and , romanized: , meaning "birth") is a geologic period that lasted from . It forms the second geologic period of the Neoproterozoic Era, preceded by the Tonian Period and followed by ...
). The crater's diameter is and its maximum depth is . It is filled with
Cambrian
The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...
sandstones 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, 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 circular 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 and
Korsholm, with a small corner belonging to
Malax.
See also
*
Impact craters in Finland
References
External links
Sundom villagetravel information page about Söderfjärden.
in Finnish impact structures homepage.
The homepageof a local exhibition site, called ''Meteoria'', in Swedish, ''Meteoriihi'' in Finnish, describing the area. Ria (riihi) is a kind of
barn, where crop is dried, and the building looks like one.
Google Earth view
Impact craters of Finland
Proterozoic impact craters
Landforms of Ostrobothnia (region)
Polders
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