سودرفیردن

thumb|250px|View of the basin of the crater remnant from Öjberget, a hill that belongs to the Rim (crater)|crater rim Söderfjärden is a polder in Ostrobothnia, western Finland, 10 kilometres south of the town of Vaasa. The plain is in an impact crater dating back to more than 640 million years ago (Proterozoic, near the end of the Cryogenian). The crater's diameter is and its maximum depth is . It is filled with Cambrian 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 wetla