When Vuoksi broke through 5,700 years ago, the flowing water eroded a channel into the fractured bedrock, which is nowadays known as Imatrankoski. The eastern side of the channel is steep and its lower section is more worn, because the flowing water eroded the schistose mica gneiss more than the resistant granite above it. The western edge of the channel on the other hand is a gentler slope and descends into the channel in the same direction as the schistosity of the mica gneiss. There are also granite boulders at the bottom of the channel which have detached from the upper part of the eastern slope. On the eastern side of the channel is the Kruununpuisto island, where flowing water has ground potholes into the rocks during Vuoksi’s early stages, when the river was wider. In the middle of the island is a group of around 50 smaller potholes, while there is a larger double pothole with open sides in the north of the island.


Coordinates: x=595347,817 y=6782867,26 (ETRS-TM35FIN)

The above coordinates are working in GPS-devices and karttapaikka.fi services.

The below coordinates are working in Google maps services.

Coordinates: 61.168663265, 28.772491377 (ETRS89 maantieteelliset(~WGS84))


Image: Arto Hämäläinen