Finland’s Magnetic Island: Jussarö, A Danger to Shipping

Coastal geology & environment, Regional History, Travel

Its been called a ghost town but the island’s massive concentration of iron ore under the sea⧆ exerts a powerful magnetic pull on passing ships and boats. The island of Jussarö is one of some 40,000 (and counting) islands off the coast that form Finland’s vast archipelago⌖.

(Image: julkaisut.metsa.fi)
(Source: Abandoned Spaces)

The “ghost town” tag comes from the closure of the island’s iron ore mining works in 1967☯ due to a decline in the world price for the mineral (‘Jussarö’, www.en.jussaro.net) …leaving the landscape scattered with the remnants of old industrial buildings abandoned to nature.

Hanneke Wrome (Image: alchetron.com)

Compass interference, a danger to shipping
The dense concentration of iron ore deposits within the island has been known to make the navigation equipment of passing vessels in the Gulf of Finland go haywire. The magnetic force emitted by the island tends to make ships malfunction and their compasses point in the wrong direction. Historically, a consequence of this has been a large incidence of marine accidents and shipwrecks in the vicinity. In 1468 the Hanseatic League cargo ship ‘Hanneke Wrome’ (or ‘Vrome’) was caught in a storm and wrecked near Jussarö island with the loss of over 200 lives and a vast quantity of expensive fabric, barrels of honey, gold coins and jewellery (‘Finland’s abandoned iron ore mine’, Abandoned Spaces, Bojan Ivanov, www.abandonedspaces.com). Perhaps the most famous shipwreck, known as “Jussarö I”, is a early 16th century ship belonging to the fleet of Swedish king, Gustav I Vasa (‘Jussarö Island’, www.visitraseborg.com). Given this hazard, Jussarö has been a haven for pilot stations and lighthouses (the island’s earliest pilot station dated from early 19th century).

Sundharu lighthouse

Raseborg’s teeth “ship trap”
Several smaller islands and islets south of Jussarö collectively known as Raseborgs gaddama (Raseborg”s Teeth”) are particularly prone to shipwrecks. This area is known to have caused disturbances in navigation as early as the 17th century. In 1751 Swedish naval cartographer “Jonas Hahn was able to explain the phenomenon by the high iron content in the underwater rock formation in the area”. The Sundharu lighthouse was stationed on one of the skerries here to try to counter the danger (‘Finnish cases: Four case study areas. Case 1 – Jussarö ship trap’, www submariner-net.eu).

When the mining activity ended, Jussarö was taken over by the Finnish Defence Forces and used for military training and urban war simulation. After the army left in 2005 the island came under the administration of Metsähallitus, a state-owned authority in charge of national parks, wildlife and forestry. The main activity today is tourism with day-trippers regularly commuting from the mainland.

Postscript: The island’s 13th century footnote in history
Jussarö first gets a mention in medieval Danish documents, appearing in King Valdemar II’s Survey (or “Court Rolls”), a document compared to William the Conqueror’s Doomsday Book record. The ‘Survey’ of Valdemar II of Denmark (reigned 1202–1241) was a land register of Danish settlements and their populations, c. 1231 (Nils Hybel, The Nature of Kingship c.800–c.1300: The Danish Incident , (2017)). Jussarö is included in the royal survey apparently because it was on the Danish route map (www.en.jussaro.net).

(Source: nationalparks.fi)

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⧆ the largest deposits of iron ore in Finland
⌖ Jussarö itself lies within the Ekenäs Archipelago
☯ the second time iron ore mining operations had been abandoned on Jussarö, previous it was mined, sometimes using Russian prisoners, from the 1830s to 1861