Märket

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title: "Märket" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["landforms-of-åland", "finnish-islands-in-the-baltic", "swedish-islands-in-the-baltic", "international-islands", "finland–sweden-border", "uninhabited-islands-of-finland", "uninhabited-islands-of-sweden", "islands-of-norrtälje-municipality", "islands-of-uppsala-county", "skerries", "former-populated-places-in-finland", "östhammar-municipality"] description: "Uninhabited skerry between Sweden and Finland" topic_path: "geography/sweden" source: "https://en.wikipedia.org/wiki/Märket" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Uninhabited skerry between Sweden and Finland ::

::data[format=table title="Infobox islands"]

Field	Value
name	Märket
native_name
image_name	Märket Island map.svg
image_caption	Märket Island with its inverted 'S' international border of 1985.
location	Baltic Sea
coordinates
area_km2	0.03
length_km	0.35
width_km	0.15
country	Finland
country_admin_divisions_title	Region
country_admin_divisions	Åland
country1	Sweden
country1_admin_divisions_title	Counties
country1_admin_divisions	Uppsala län
country1_admin_divisions_1	Stockholms län
population	0
timezone1	EET and CET
module	{{Infobox lighthouse
qid	Q3378321
image_name	Märket lighthouse.jpg
location	Märket Islet, Baltic Sea
coordinates
yearbuilt	1885
automated	1979
construction	stone and cast iron tower
shape	cylindrical tower on an octagonal basement rising from a 2-story keeper’s house
marking	white tower and lantern
height	14 m
focalheight	17 m
characteristic	Fl W 5s.
::

::callout[type=note] the island ::

| name = Märket | native_name = | image_name = Märket Island map.svg | image_caption = Märket Island with its inverted 'S' international border of 1985. | location = Baltic Sea | coordinates = | area_km2 = 0.03 | length_km = 0.35 | width_km = 0.15 | country = Finland | country_admin_divisions_title = Region | country_admin_divisions = Åland | country1 = Sweden | country1_admin_divisions_title = Counties | country1_admin_divisions = Uppsala län | country1_admin_divisions_1 = Stockholms län | population = 0 | timezone1 = EET and CET | module = {{Infobox lighthouse|embed=yes | qid = Q3378321 | image_name = Märket lighthouse.jpg | location = Märket Islet, Baltic Sea | coordinates = | yearbuilt = 1885 | automated = 1979 | construction = stone and cast iron tower | shape = cylindrical tower on an octagonal basement rising from a 2-story keeper’s house | marking = white tower and lantern | height = 14 m | focalheight = 17 m | characteristic = Fl W 5s.

Märket ('The Mark', ) is a 3.3 ha uninhabited skerry in the Baltic Sea shared by Sweden and Finland (in the area of the autonomous region Åland), with a lighthouse as its salient humanmade feature. Märket has been divided between the two countries since the Treaty of Fredrikshamn of 1809 defined the border between Sweden and Grand Duchy of Finland as going through the middle of the island. The Finnish side of the island is part of the Municipality of Hammarland in the autonomous region of Åland and is the westernmost land point of Finland. The Swedish part of the island is itself divided between two counties of Sweden: Uppsala County (Östhammar Municipality) and Stockholm County (Norrtälje Municipality).

Geography and history

::figure[src="https://upload.wikimedia.org/wikipedia/commons/b/b8/Marketmap.png" caption="Märket Island with the international border and the county border on the Swedish part"] ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/b/b6/Märket_in_Sweden.png" caption="Location of Märket Island"] ::

The 6 NM Understen–Märket Passage links the Bothnian Sea to the Baltic proper. The skerry is roughly 350 m long by 150 m wide, and has an area of about 3.3 ha. The island is gaining height due to post-glacial rebound, and was probably underwater before the 1500s.

Märket is the smallest sea island shared by two countries. It used to have a straight border until the Grand Duchy of Finland built the lighthouse on the Swedish side and then, they had to change the border. The name Märket ('the Mark') probably comes from its usefulness as a navigation mark before there were lighthouses. The route between Sweden and Åland has a passage about 15 NM long over open sea. Before the lighthouse was erected, the island and its shallows were dangerous navigational hazards, which seafarers tried desperately to avoid. In 1873, as many as 23 ships were grounded on the Swedish coast and its archipelago trying to avoid Märket, and eight of them were shipwrecked. Märket is detached from the main Åland archipelago, with the closest island more than 10 km away, and the closest harbor, Berghamn, 23 km away in Eckerö. There is no deep harbor; the island can only be reached with boats. There are small, barely surfacing rocks northwest of Märket, called Märketshällor ("stones of Märket"), which are too small to sustain vegetation.

The island consists of mostly smooth diabase rock, with a maximum natural elevation of 2 m. Most of the area is regularly washed over with seawater in storms, and scoured by drift ice in winter. Plant life, which is limited to low-growing grasses and herbs, persists only in some protected spots. Twenty-three plant species have been identified altogether. The halophilic grass Puccinellia capillaris and the herbaceous Sagina nodosa (knotted pearlwort) are found scattered throughout the island. Among rarer species, Spergularia marina (salt sandspurry) grows on Märket. Salix caprea (goat willow) grows on an abandoned building.

There are large grey seal communities around Märket, and the island has been a target for seal safaris.

International border and lighthouse

::figure[src="https://upload.wikimedia.org/wikipedia/commons/4/47/Märket_Lighthouse,_Finland_IMG_3374.jpg" caption="The island lighthouse"] ::

There is a lighthouse on the Finnish side of the current border, which has been unmanned and automated since 1979. When it was built by the Grand Duchy of Finland in 1885, the island was considered a no-man's land, so the lighthouse was simply built upon the highest point of the island. However, the location selected was within the Swedish portion of the island. Though the lighthouse was formally on the Swedish side of the border, it was never considered Swedish, nor administered from Sweden.

As a result, the border was adjusted in 1985 so that the lighthouse is now located on Finnish territory. The adjustment was carried out such that no net transfer of territory occurred, and the ownership of the coastline was unchanged so as not to interfere with each country's fishing rights.

This resulted in an unusual shape for the international border to satisfy both Finnish and Swedish interests. The adjusted border takes the form of an inverted 'S', and the lighthouse is connected to the rest of Finland only by a short stretch of land. The border on the island is around 480 m long. The border is regularly resurveyed every 25 years by officials representing both countries. The last such joint inspection took place in August 2006. The border is marked by holes drilled into the rock, because the seasonal drift ice would shear off any protruding markers. Because of the Nordic Passport Union and the Schengen Agreement, there have been no passport checks or other border formalities at the border since 1958, so intra-Nordic/intra-Schengen visitors may visit the island freely.

The lighthouse has been automated since 1979 and the surrounding buildings are no longer used. The increasing general availability of GPS has made the lighthouse's primary function redundant.

Radio amateurs activity

Radio amateurs around the world consider the Finnish part of Märket (Märket Reef or Market Reef as they call it) a separate entity, distinct from Finland, the Åland Islands and Sweden. The Finnish part of Märket Reef used to be one of the world's most desired "countries" to contact among radio amateurs because of its special status and relative remoteness. One or more amateur radio expeditions to the island occur most years, weather permitting. During these expeditions, tens of thousands of radio contacts are made with people in several parts of the world. At high seas, landing is only possible with a helicopter. Pictures of Märket are shown on QSL cards. The official prefix for use on the Finnish side is OJ0 call sign prefix for Märket Reef. An OJ0 vanity callsign can be obtained, for a fee, from Traficom.fi, the Finnish Transport and Communication Agency. Amateurs with licenses in countries supporting CEPT can operate from the reef while using the OJ0/ prefix in front of one's own call sign. All radio activity on the island is by visitors on DX-peditions. When the Finnish part of the reef was given its special status in amateur radio, in the late 1960s the lighthouse keeper himself became a licensed amateur radio operator, who initially used the call OH0MA. On the Swedish side of Märket Reef, the call signs 8S9M and SI8MI have been used.

Climate

Märket has a continental climate affected by oceanic influences; it has a reputation for being one of the windiest places in Finland. A meteorological station has been managed by the lighthouse keepers since 1896, and an automatic station of the Finnish Meteorological Institute was inaugurated on 10 November 1977, shortly before its automation.

The effect of the sea is very important to the climate of the island; thermal inertia dramatically reduces the temperature fluctuations during the year compared to those of the continent, and to a lesser extent, those of the central part of Fasta Åland, the largest island of the archipelago of Åland. Märket holds five records for daytime temperatures among Finnish weather stations, all in the period between 29 November and 1 January, with 10.2 °C on 15 December 2006, and 8.8 °C on 31 December 1975. The average yearly temperature is roughly 6 °C and is one of the highest in Finland, with the month of January being milder than on the continent (-2.5 °C on average), and a warm summer (15.9 °C on average in July). The island is drier than the mainland; the average annual rainfall does not usually surpass 550 mm.

| location = Hammarland Märket (1991–2020 normals, extremes 1995- present) | collapsed = | metric first = Yes | single line = Yes | Jan record high C = 9.3 | Feb record high C = 9.0 | Mar record high C = 12.8 | Apr record high C = 15.5 | May record high C = 23.3 | Jun record high C = 24.8 | Jul record high C = 27.8 | Aug record high C = 26.0 | Sep record high C = 23.1 | Oct record high C = 18.2 | Nov record high C = 13.6 | Dec record high C = 10.3 | year record high C = 27.3 | Jan mean C = -0.1 | Feb mean C = -1.2 | Mar mean C = 0.4 | Apr mean C = 2.9 | May mean C = 6.5 | Jun mean C = 11.5 | Jul mean C = 16.0 | Aug mean C = 16.5 | Sep mean C = 12.9 | Oct mean C = 8.0 | Nov mean C = 4.2 | Dec mean C = 1.6 | Jan record low C = -13.7 | Feb record low C = -19.4 | Mar record low C = -10.3 | Apr record low C = -4.0 | May record low C = -1.3 | Jun record low C = 4.2 | Jul record low C = 8.2 | Aug record low C = 7.7 | Sep record low C = 4.2 | Oct record low C = -1.7 | Nov record low C = -8.3 | Dec record low C = -10.7 | year record low C = -19.4 | source 2 = Extremes 1995-present{{cite web | url = https://kilotavu.com/fmi-tilastot.php?taulukkomoodi=true | title = FMI open data | publisher = FMI | access-date = 6 July 2025}} | source = 1991-2020 FMI normals{{cite web | url = https://www.ilmatieteenlaitos.fi/1991-2020-lampotilatilastot | title = 1991-2020 FMI normals | publisher = FMI | access-date = 22 April 2023}}

References

References

1. {{cite rowlett. ala
2. [http://kansalaisen.karttapaikka.fi/kartanhaku/paikannimihaku.html?query=hae&hakutapa=paikannimihaku&nimi=M%C3%A4rket&kunta=&cx=3454345&cy=7216161&scale=8000000&tool=siirra&styles=normal&lang=en-GB citizen's Map Site – National Land Survey of Finland]
3. Frank Jacobs. (24 April 2012). "One Island, Two Countries". [[The New York Times]].
4. Frank Jacobs. (24 April 2012). "One Island, Two Countries". The New York Times.
5. [http://www.worldislandinfo.com/SUPERLATIVESV2.html World island superlatives]
6. Tom Backmansson, 1998. TV series "Fyren - Majakka", episode 10: Märket. First shown on Yle TV1, 16 July 2000 17.59. Produced by Yleisradio Oy, http://areena.yle.fi/1-682613 https://www.youtube.com/watch?v=ytNqj9QfG70
7. (1998). "Märket - en märklig ö". Daphne.
8. "Hyljesafari".
9. [http://www.bsis.org/Dokument/1998-2%20Market.pdf ''Märket – a remarkable island''] {{Webarchive. link. (27 October 2017 by Joakim Ekman, Lars-Gunnar Bråvander, Gabriel Ekmand, and Ebbe Zachrisson {{in lang). sv includes a map of the island
10. [[Lantmäteriet]]. (28 November 2024). "Min karta".
11. Shifting Territories: Märket Reef, [http://www.hiddeneurope.co.uk/article_info.php?articles_id=272 Hidden Europe Magazine], 11 (November 2006), pp. 26–29.
12. https://dxnews.com/market-reef-mistake/
13. "Islands on the Air - IOTA Directory - Group Information".
14. {{in lang. fi [http://www.majakkaseura.fi/fin/market/nain_matkustat_marketille/ Association finlandaise des phares] {{webarchive. link. (27 September 2007 – Presentation of the Island)
15. {{in lang. fi [http://www.ilmatieteenlaitos.fi/saa/havainto_20.html Institut météorologique national de Finlande] – A list and characteristics of the meteorological stations of Finland
16. {{in lang. fi [http://www.fmi.fi/saa/tilastot_66.html Institut météorologique national de Finlande] – Statistiques nationales pour le mois de décembre
17. {{in lang. link. (14 October 2007 – Statistiques générales sur Åland)
18. {{in lang. en [http://www.fmi.fi/weather/climate_6.html Institut météorologique national de Finlande] {{Webarchive. link. (27 April 2010 – Statistiques climatiques de la période 1971–2000)

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::