A story in Helsingin Sanomat (€) about a deserted lighthouse on a small reef caught my attention last Sunday.

Located about 20 kilometres off and between the shores of Åland and Sweden, Märket reef surfaced in 1700s as a result of post-glacial rebound, ie. the rising of land. Waters here became increasingly dangerous to ships sailing between Gulf of Bothnia and Baltic Proper and a lighthouse needed to be built.

In 1809 however, Russian Empire invaded Finland and for some reason this rock became split with Sweden in the process of drawing the border between the new Grand Duchy of Finland and the Kingdom of Sweden. Eventually the Swedes persuaded the Russians to build a lighthouse on Märket, which was completed in 1885. It was soon discovered, that it was actually built on the Swedish half.

The reef has since risen one metre more from the sea and gained more land area. The lighthouse was automated and left unmanned in 1976. Five years later it was agreed to move the border so, that the lighthouse became a part of Finland and Sweden was accordingly compensated 0,4 hectares of unbuilt reef. For this micromanagement to be complete, the border had to be given the above illustrated S-shape. The area of each country's possessions had to remain unchanged and the coastline too – rearrangement would have unnecessarily interfered with each country's fishing rights.

As if this wasn't technical enough, the new border had to be acknowledged by eight other European countries. Namely those who had signed the Treaty of Åland in 1921, which established the autonomous and demilitarised status of the Åland Islands. That deal came too late for Märket's sister lighthouse on Bogskär, which was fired down in the first world war.

Radio amateurs have always had special interest in the 350 x 150 m reef. It is the world's smallest sea island with an international border, quite inaccessible and treated, apparently incorrectly, as an exclave of Finnish territory. Temporary radio stations set up by yearly expeditions have a callsign of their own and an exlusive QSL card to be sent to those radio amateurs, who've been in contact with the reef.

The Finnish Lighthouse Assosciation is raising funds for the renovation of the lighthouse. It is too rugged to attract more tourists than storm chasers or marine biologists, but it could additionally act as an outpost for climate change research, because of its precarious affair with sea levels and geology.