Skerries are most commonly formed at the outlet of fjords where submerged glacially formed valleys at right angles with the coast join with other cross valleys in a complex array. In some places near the seaward margins of fjorded areas, the ice-scoured channels are so numerous and varied in direction that the rocky coast is divided into thousands of island blocks, some large and mountainous while others merely rocky points or rock reefs, menacing navigation.
Examples
The island fringe of Norway is such a group of glacially formed skerries (called a skjærgård); many of the cross fjords are so arranged that they parallel the coast and provide a protected channel behind an almost unbroken succession of mountainous islands and skerries. By this channel one can travel through a protected passage almost the entire 1,600 km route from Stavanger to North Cape, Norway. The Blindleia is a skerry-protected waterway that starts near Kristiansand in southern Norway, and continues past Lillesand.
The Swedish coast along Bohuslän is likewise skerry guarded. Even the east coast of Sweden, in the Baltic sea has many big skärgårdar (archipelago) , notably Stockholm archipelago - Stockholms skärgård - skjærgård.
The southwestern coast of Finland also has a large amount of skerries, so many, in fact, that they form an archipelago.
