Söderfjärden is a plain

Plain

In geography, a plain is land with relatively low relief, that is flat or gently rolling. Prairies and steppes are types of plains, and the archetype for a plain is often thought of as a grassland, but plains in their natural state may also be covered in shrublands, woodland and forest, or...

 in Ostrobothnia

Ostrobothnia (region)

Ostrobothnia is a region of Finland. It is located in Western Finland. It borders the regions Central Ostrobothnia, Southern Ostrobothnia, and Satakunta and is one of the four regions making up the historical province of Ostrobothnia....

, western Finland

Finland

Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

, just 10 kilometres south of the town of Vaasa

Vaasa

Vaasa is a city on the west coast of Finland. It received its charter in 1606, during the reign of Charles IX of Sweden and is named after the Royal House of Vasa...

. The plain is located in an impact crater

Impact crater

In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 some 560 million years old (late Ediacaran

Ediacaran

The Ediacaran Period , named after the Ediacara Hills of South Australia, is the last geological period of the Neoproterozoic Era and of the Proterozoic Eon, immediately preceding the Cambrian Period, the first period of the Paleozoic Era and of the Phanerozoic Eon...

). The crater has a diameter of 6.6 km and a maximum depth of 300 metres. It is filled with Cambrian

Cambrian

The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...

 sandstone

Sandstone

Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...

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

Post-glacial rebound is the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period, through a process known as isostasy...

, Söderfjärden was a wetland but was later drained. It is currently cultivated and is very 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 under water.

External links

• Sundom village travel information page about Söderfjärden.
• Söderfjärden in Finnish impact structures homepage.
• The homepage of a local exhibition site, called Meteoria, in Swedish, Meteoriihi in Finnish and English, describing the area. Ria (riihi) is a kind of barn
  Barn
  A barn is an agricultural building used for storage and as a covered workplace. It may sometimes be used to house livestock or to store farming vehicles and equipment...
  
  , where crop is dried, and the building looks like one.