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

Finnish Finnish may refer to: * Something or someone from, or related to Finland * Culture of Finland * Finnish people or Finns, the primary ethnic group in Finland * Finnish language, the national language of the Finnish people * Finnish cuisine See also ...

petrologist Petrology () is the branch of geology that studies rocks and the conditions under which they form. Petrology has three subdivisions: igneous, metamorphic, and sedimentary petrology. Igneous and metamorphic petrology are commonly taught together ...

most associated with his studies of

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

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

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

to allow him to work outdoors. After studying first in

Helsinki Helsinki ( or ; ; sv, Helsingfors, ) is the capital, primate, and most populous city of Finland. Located on the shore of the Gulf of Finland, it is the seat of the region of Uusimaa in southern Finland, and has a population of . The city ...

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

Heidelberg Heidelberg (; Palatine German language, Palatine German: ''Heidlberg'') is a city in the States of Germany, German state of Baden-Württemberg, situated on the river Neckar in south-west Germany. As of the 2016 census, its population was 159,914 ...

, Sederholm returned to Finland to work for the

Geological Survey of Finland The Geological Survey of Finland ( fi, Geologian tutkimuskeskus abbreviated GTK, sv, Geologiska forskningscentralen) is the geological survey of Finland. The organization was founded in 1885 when Emperor Alexander III decreed that the Geological ...

. 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 basement rocks, Sederholm instigated a

map-making Cartography (; from grc, χάρτης , "papyrus, sheet of paper, map"; and , "write") is the study and practice of making and using maps. Combining science, aesthetics and technique, cartography builds on the premise that reality (or an im ...

programme that, between 1899 and 1925, published many maps and descriptions of their geological history.

Gneiss Gneiss ( ) 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. Gneiss forms at higher temperatures a ...

es in the areas he studied (the so-called Baltic Shield) were often of mixed composition, with layers of

granitic A granitoid is a generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz- ...

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 of

igneous Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or ...

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

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

Murchison Medal The Murchison Medal is an academic award established by Roderick Murchison, who died in 1871. First awarded in 1873, it is normally given to people who have made a significant contribution to geology by means of a substantial body of research and ...

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 The Penrose Medal was created in 1925 by R.A.F. Penrose, Jr., as the top prize awarded by the Geological Society of America. Originally created as the Geological Society of America Medal it was soon renamed the Penrose Medal by popular assent of t ...

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. Hitch ...

(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 ''Suomen maapäivät'', later ''valtiopäivät''; Swedish ''Finlands Lantdagar''), was the legislative assembly of the Grand Duchy of Finland from 1809 to 1906 and the recipient of the powers of the Swedish Ri ...

, and undertook missions from this to the

League of Nations The League of Nations (french: link=no, Société des Nations ) 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 that ...

. He was also a member and chairman (twice) of the Economic Society of Finland. In the 1974 historical novel ''

Centennial {{other uses, Centennial (disambiguation), Centenary (disambiguation) A centennial, or centenary in British English, is a 100th anniversary or otherwise relates to a century, a period of 100 years. Notable events Notable centennial events at ...

'',

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 in particular geographic locales and ...

listed Sederholm among those scientists who made early estimates of the age of the Earth. 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 (Latin for "British Encyclopædia") is a general knowledge English-language encyclopaedia. It is published by Encyclopædia Britannica, Inc.; the company has existed since the 18th century, although it has changed ownership various t ...

)
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)
Sederholmite mineral data
(WebMineral.com) 1863 births 1934 deaths Finnish geologists Petrologists Penrose Medal winners Members of the Royal Society of Sciences in Uppsala {{geoscientist-stub