Jakob Johannes Sederholm (20 July 1863 – 26 June 1934) was a Finnish

petrologist Petrology () is the branch of geology that studies rocks, their mineralogy, composition, texture, structure and the conditions under which they form. Petrology has three subdivisions: igneous, metamorphic, and sedimentary petrology. Igneous an ...

most associated with his studies of

migmatite Migmatite is a composite rock (geology), rock found in medium and high-grade metamorphic environments, commonly within Precambrian craton, cratonic blocks. It consists of two or more constituents often layered repetitively: one layer is an old ...

s. Troubled by illness throughout his life, Sederholm originally chose to study

geology Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...

to allow him to work outdoors. After studying first in

Helsinki Helsinki () is the Capital city, capital and most populous List of cities and towns in Finland, city in Finland. It is on the shore of the Gulf of Finland and is the seat of southern Finland's Uusimaa region. About people live in the municipali ...

(where he was a student of Fredrik Johan Wiik), then in

Stockholm Stockholm (; ) is the Capital city, capital and List of urban areas in Sweden by population, most populous city of Sweden, as well as the List of urban areas in the Nordic countries, largest urban area in the Nordic countries. Approximately ...

and

Heidelberg Heidelberg (; ; ) is the List of cities in Baden-Württemberg by population, fifth-largest city in the States of Germany, German state of Baden-Württemberg, and with a population of about 163,000, of which roughly a quarter consists of studen ...

, Sederholm returned to Finland to work for the Geological Survey of Finland. In 1893 he assumed the role of director of this institution, a post he occupied until his death forty years later. Working on local

Precambrian The Precambrian ( ; or pre-Cambrian, sometimes abbreviated pC, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of t ...

basement rock In geology, basement and crystalline basement are crystalline rocks lying above the mantle and beneath all other rocks and sediments. They are sometimes exposed at the surface, but often they are buried under miles of rock and sediment. The baseme ...

s, Sederholm instigated a map-making programme that, between 1899 and 1925, published many maps and descriptions of their geological history.

Gneiss Gneiss (pronounced ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. This rock is formed under p ...

es in the areas he studied (the so-called

Baltic Shield The Baltic Shield (or Fennoscandian Shield) is a segment of the Earth's crust belonging to the East European craton, East European Craton, representing a large part of Fennoscandia, northwestern Russia and the northern Baltic Sea. It is composed ...

) were often of mixed composition, with layers of

granitic A granitoid is a broad term referring to a diverse group of coarse-grained igneous rocks that are widely distributed across the globe, covering a significant portion of the Earth's exposed surface and constituting a large part of the continental ...

rock being interleaved with

metamorphic rock Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, caus ...

. Sederholm termed these as

s, and viewed them as the product of the

intrusion In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

igneous Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

into metamorphic rocks at depth. During his career Sederholm received both the Murchison Medal from the

Geological Society of London The Geological Society of London, known commonly as the Geological Society, is a learned society based in the United Kingdom. It is the oldest national geological society in the world and the largest in Europe, with more than 12,000 Fellows. Fe ...

(1928) and the Penrose Medal from the

Geological Society of America The Geological Society of America (GSA) is a nonprofit organization dedicated to the advancement of the geosciences. History The society was founded in Ithaca, New York, in 1888 by Alexander Winchell, John J. Stevenson, Charles H. Hi ...

(also 1928). The mineral sederholmite is named in his honour. Aside from his geological work, Sederholm was a member of the

Diet of Finland The Diet of Finland (Finnish language, Finnish ''Suomen maapäivät'', later ''valtiopäivät''; Swedish language, Swedish ''Finlands Lantdagar''), was the Diet (assembly), legislative assembly of the Grand Duchy of Finland from 1809 to 1906 ...

, and undertook missions from this to the

League of Nations The League of Nations (LN or LoN; , SdN) was the first worldwide intergovernmental organisation whose principal mission was to maintain world peace. It was founded on 10 January 1920 by the Paris Peace Conference (1919–1920), Paris Peace ...

. From 1921 to 1923, he led the League of Nations' " Commission of Enquiry in Albania" in the

Principality of Albania The Principality of Albania () was a monarchy from 1914 to 1925. It was headed by Wilhelm, Prince of Albania, and located in modern Albania in the Balkans, Balkan region of Europe. The Ottoman Empire owned the land until the First Balkan Wa ...

. He was also a member and

chairman The chair, also chairman, chairwoman, or chairperson, is the presiding officer of an organized group such as a board, committee, or deliberative assembly. The person holding the office, who is typically elected or appointed by members of the gro ...

(twice) of the Economic Society of Finland. In the 1974

historical novel Historical fiction is a literary genre in which a fictional plot takes place in the setting of particular real historical events. Although the term is commonly used as a synonym for historical fiction literature, it can also be applied to oth ...

Centennial A centennial, or centenary in British English, is a 100th anniversary or otherwise relates to a century. Notable events Notable centennial events at a national or world-level include: * Centennial Exhibition, 1876, Philadelphia, Pennsylvania. ...

'',

James Michener James Albert Michener ( or ; February 3, 1907 – October 16, 1997) was an American writer. He wrote more than 40 books, most of which were long, fictional family sagas covering the lives of many generations, set in particular geographic locales ...

listed Sederholm among those scientists who made early estimates of the

age of the Earth The age of Earth is estimated to be 4.54 ± 0.05 billion years. This age may represent the age of Earth's accretion (astrophysics), accretion, or Internal structure of Earth, core formation, or of the material from which Earth formed. This dating ...

. Sederholm's estimate was 40 million years.

Papers

* ''Hackman V.'
Jacob Johannes Sederholm
Biographic notes and bibliography // Bulletin de la Commission géologique de Finlande. 1935. N 112. 34 p. * ''Papunen H.'
Jakob Johannes Sederholm – geologi, humanisti ja totuudenetsijä
// Geologi. 2009. N 2. P. 35-38.

References

External links

Biographical entry
(

Encyclopædia Britannica The is a general knowledge, general-knowledge English-language encyclopaedia. It has been published by Encyclopædia Britannica, Inc. since 1768, although the company has changed ownership seven times. The 2010 version of the 15th edition, ...

)
Sederholm, Johannes Jakob
Complete Dictionary of Scientific Biography, 2008.
Jakob Johannes Sederholm
- Lithos, 2010.
Murchison Medal winners
(Geological Society of London)

(Geological Society of America)

(

Mindat.org Mindat.org is a non-commercial interactive online database covering minerals around the world. Originally created by Jolyon Ralph as a private project in 1993, it was launched as a community-editable website in October 2000. it is operated by ...

)
Sederholmite mineral data
(WebMineral.com) 1863 births 1934 deaths Finnish geologists Petrologists Penrose Medal winners Members of the Royal Society of Sciences in Uppsala Geologists from the Russian Empire People from the Grand Duchy of Finland Finnish expatriates in Albania Murchison Medal winners People from Helsinki {{geoscientist-stub