In the Kvarken land uplift occurs at about 8–9 mm per year and has a major impact on our nearby nature. Land uplift is caused by the most recent Ice Age, which ended 10,000 years ago. During the Ice Age the continental ice pressed the Earth’s crust downwards. When the ice melted, the crust began to slowly rise again and a phenomenon was created that we still see today as land uplift on seashores and in their vicinity.
Land uplift occurs throughout the Baltic Sea area, but it is strongest in the Kvarken region. Although climate change is raising sea levels, in the Vaasa region the land is still rising faster than the sea.
Impact on shoreline nature
Land uplift continuously changes the shoreline as the waterline slowly shifts farther away. New land emerges from the sea, into which vegetation and wildlife gradually expand. Succession, that is the gradual change of species over time, is a natural progression on uplift coasts.
Vegetation areas on uplift coasts form distinct zones. Nearest the water grow grasses and reeds adapted to submerged conditions and tolerant of occasional submersion. Herbaceous vegetation transitions into a shrub zone, where species such as sea buckthorn can grow. The shrub zone gradually becomes a deciduous forest above the shoreline, with species such as grey alder and black alder and various willows. On drier ground the deciduous forest gives way to spruce-dominated coniferous forest and only the highest areas host pine.
Shoreline overgrowth and sedimentation accelerate the effects of land uplift.
Impact on built shorelines
Constructed shores do not show the same zonation as natural shores. Because of land uplift harbours become shallower and old piers stand on dry land. Land uplift lowers coastal waters and causes, among other things, a need to dredge navigation channels and to relocate and rebuild harbours closer to deeper waters.
In Vaasa the harbour location has been changed several times due to land uplift. For example, in Suvilahti you can see old stone quays on dry land. Former seafloor is also used as fields and pastures because of its flatness and nutrient richness.
Fladas and gloe lakes
Land uplift also transforms sea bays over time. As a result of land uplift bays gradually become cut off from the sea, first forming fladas and later gloe lakes. At first the bay is still connected to the sea. As the land rises the bay becomes a flada with only a narrow water connection to the sea. As the land continues to rise the flada turns into a gloe lake, into which seawater reaches only more rarely, mainly during storms and high tides. Eventually the area separates completely from the sea and wetland vegetation spreads along the shores of the gloe lake.
Fladas and gloe lakes are important for biodiversity because they provide valuable habitats for many species. Fladas and gloe lakes are, for example, spawning grounds for many fish such as perch, roach and pike. In addition they serve as resting and breeding areas for birds and provide sheltered habitats for insects.
