Sederholm, Johannes Jakob

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(b. Helsinki, Finland, 20 July 1863; d Helsinki, 26 June 1934)

geology, petrology.

Sederholm was the third eight children of Clase Theodor Sederholm and Maria Sofia Christina Blomquist, His father, owner of a printing plant, founded and published the major daily newspaper of Helsinki and also published books. In 1882 Sederholm entered the University of Helsinki to study philosophy. His health was weak, however, and his doctor, doubtful of his recovery, recommended that he abandon formal academic pursuits for a branch of the natural science that would get him outdoors. he chose geology. Sederholm had to fight against illness throughout his life.

In the department of natural history at Helsinki, Sederholm met Axel Palmen, later a renowned ornithologist, and Wilhelm Ramsay, who became a leading geologist of Fennoscandia; they became lifelong friends. After receiving his B.A. in 1885, Sederholm continued his studies from 1886 to 1888 at the University of Stockholm, where he met Brøgger, who was teaching mineralogy and geology there. His imposing, multifaceted personality inspired several generations of Fennoscandian geologists, and Sederholm always spoke of him as “my dear teacher and master”;they remained life long friends.

During the summers Sederholm served as assistant geologist(1883–1887), and in 1888 was appointed a member, of the Geological commission (Geological Survey), To become more with familiar modern trends in ptrology, he studied with Rosenbhush at Heidelberg, where he met American geologists and thus began a lifelong link with America. Sederholm completed two important papers while at Heidelberg, on the eruptive rocks of southern Finland and on the rapkivi granties. metamorphosed and that two degrees of metamorphism can be distinguished, an idea that two degrees of metamorphism can be distinguished, an idea that was developed (metamorphic dept Zones) more than ten years later by Becke and Grubenmann. The paper on the rapakivi granites market the starting point of research that remained a lifelong concern. The former was also presented as dissertation on 30 May 1861 with F.J.Wiik, a declared antiactualist, as critic.

After having passed his examination in 1892, Sederholm received the doctorate at the age of twenty-nine, become director of the Geological Commission, and married Anna Ingeborg Mathilde von Christierson. They had two daughters and one son. As director of the Geological commission for over forty years, he not only created a modern research institution for basic and economic geology but also established new standards for the study of the world’s crystalline basements, the Precambrain continental shields. He retired during the summer of 1933 and died the following June.

Established in 1877 under the directorship of Karl Adolf Moberg, the Geological Commission was the first geological survey of Finland with geological mapping. The first sheet appeared in 1879 on a scale of 1:200,2000; bedrock and superficial deposits were represented on the same sheet. Thirty-seven quardrangles of this atlas were subsequently published, but only a few principle pertrolotical groups were distinguished within the basement. Under Sederhoim’s enthusiatic leadership, however, another type of map was adopted, with bedrock and superficial deposits published on separate sheets on a scale of 1:400,00. Whereas the earlier maps had been based on petrological distinctions, the new series employed principles proposed in Sederholm’s paper of 1893. Age relationships were of primary importance, but the methods of classical straigraphy were scarcely applicable: and new principles for deter mining the succession of geological events were needed. During the course of th8is long and exacting work, methods and classifications were constantly adjusted to conform with the growth of knowledtge and were influenced by critics and exchanges with other geologists. The continuintg feedback from field observations modified and improved the manner of mapping over the years. The dominant thread was always actualism.

One of the methods chiefly responsible for the final success of the survey was Sederholm’s idea of mapping crucially important areas or outcrops on a finer scale, and the geology of Finland was thus represented at different enlargements. Some outcrops were mapped at 1:10, others at 1:50, 1:200, or 1: 10,000. in the limit, photographs of ice-smoothed hillocks, of hand speciemens, and of thin sections under the microscope completed the spectrum of scales.

With Sederholm’s method of multiple levels of research, Finland became the classic example of a Precambrian basement: for in addition to various mapping scales, the Commission was also administered at various levels of organization. In this way the project, rather than becoming merely the sum of its parts, acquired new properties and the individual parts assumed new functions at different levels. Studies conducted at each lev3el had their own methodology and governing principles. Because of qualitative differences, the same methods of study are best applied to closely related levels. This distinction between different levels was not understood by those who sought a unity of methods to study the entire spectrum: for instance, those who advocated mapping only petrographic differences without paying attention to formations having the same or a different geological history.

The large units of sedimentary and volcanic formations are separated by unconformities, breaks in geological history that are most evident if they are marked by conglomerates representing specimens of a former erosional surface. Sederholm’s eagerness to find conglomerates was rewarded by his important discovery of such formations in the sedimentary series of Lake Näsijärvi, near Tampere, in 1899. Many other sedimentary structures are well preserved, such as the varves containing some of the very ancient fossils Corycium enigmaticum. This was a triumpth for uniformitarian principles, and the area became a classic that was often visited by foreign geologists. Another important member of these series consists of basic volcanic rocks transformed into uraliteporphyrites.

In order to obtain a uniformitarian picture of the events that occurred in the Svecofennian area of the Precambrian basement, it was necessary to find the basement supporting the sedimentary series and the piles of volcanic effusions, as well as the source areas for the clastic rocks. But again, new obstacles appeared that could not be eliminated unitl the posibility of the reactivation of old basements was recognized. Observations of relevant exposures were described, and interpretive principles proposed, in 1897, when an official excursion of the Seventh International Geological Congress visited the shores of Näsijärvu; these views spread rapidly and soon aappeared in textbooks.

Dikes of volcamic and granitic intrusions wi5th their ramifications provided, by their intersections, still another means of establishing a chronological sequence; but continuing in this way, geologists soon became ensnared in riddles that at first sight appeared insoluble. Before further progress was possible, such problems had to be pursued on several levels. During the summer of 1906 Sederholm, then a member of the Diet, was obliged to remain near Helsinki and was unable to travel to the wilderness. He decided to study the Roches moutonnées of southern Finland with his assistant Hans Hausen. The multitude of phenomena of these southern rocks, varying from one step to the next although the number of mineral components and their combinations were sharply limited, was initially extremely confusing. These phenomena were only partly intelligible through methods of classical petrology, for which reason they had not been observed earlier, even though they occupy vast areas in crystalline basements of any age. A new set of ideas and methods was needed to describe and interpret the observations and to enable others to see these phenomena. Thus a new level of research was intercalated between the petrographic level, based mainly on microscopic study, and large-scale mapping. After the variegated patterns visible on the flat rock surfaces of southern Finland were mapped on scales form 1:10 to 1:200, an unsuspected wealth of new phenomena was revealed and time sequences were established. The apparatus of descriptive and interpretive terms that was created gave petrologists of the old school cause to shudder. Nevertheless, a new domain, existing from unknown ages and hitherto invisible, was revealed: and a new model for mass circulation within the sialic crust was proposed.

The mixed rocks, previously considered impure, were named migmatites and became the center of petrologic interest. Different patterns of such mixed rocks were distinguished, from “agmatities” (with angular fragments) to “nebulites” (with cloudy appearance), and from ptygamatic veins to palingenetic and analectic granites (older granites, gneisses, or schists grading into rocks that resembled granite). Sederholm considered these areas to be former “granite factories” or “granite works” (1907) arrested during their activity by cooling and rendered accessible by deep erosion, smoothed by glacial polishing, and washed bare by wave action. A new cyclic model was proposed, similar in some points to Hutton’s hypothesis; but in this sequence every phase was represented by visible outcrops, so that the whole of the events could be observed in the field. It was a new victory for uniformitarianism. The granites in the model came not from “unknown depths,” as a result of differentiation from a basic magma, but from reactivation in Situ of older materials (anatexis and palingenesis). These mobilized granites could then rise in the crust.

The case of the “paradoxical inclusions” illustrates the sort of problem that confronted Sederholm and his method of solution. These inclusions are both older and younger than the enclosing rocks. The explanation was that basic dikes were intruded into former gneisses or schists, which were later reactivated and transformed into palingenetic granite enclosing the fragments of the former dikes. These phenomena made it possible to distinguish the chronological sequence of events in areas characterized as ultrametamorphic and to coordinate these sequences over more extended areas.

On another level, belts characterized by distinct historical evolution could be distinguished and mapped, some with definite limits (such as the Karelian belt, well discernible from the much older basement in eastern Karelia) or more indistinct (such as the Svecofennian belt in southern Finland, characterized by the Bottnian formation). Sederholm published a series of maps of the basement of Finland, perfected after the progressive mapping. Most of them were included in the Atlas of Finland, a work in which he was deeply interested.

The study of fracture patterns cutting the old basement was conducted on the scale of the old shield (1911, 1913, 1932). After the deep erosion that removed the upper zones and exposed the metamorphic and ultrametamorphic levels, the brittle crust was broken into a mosaiclike patternm undergoing weathering, erosion, and glacial scouring, and thus producing some of the most characteristic features of the Fennoscandian landscape.

In “The Average Composition of the Earth’s Crust in Finland” (1925), another study of old crystalline basements, Sederholm attempted to characterize the average geochemical composition of deeply eroded crystal areas. The investigation differed from the usual mend of rock analyses (for example, Frank Wigglesworth Clarke’s) because the analyses entering into the calculation were weighted according to the areas actually underlain by the corresponding rocks. By establishing the weighted average composition, the result offered a valuable example-the only one thus far-of an extended crystalline basement cut at this deep level and represented an important contribution to the geochemical knowledge of the sialic crust.

Sederholm was a keen observer for whom a granite was not an abstract concept but the embodiment of a distinct “personality.” Appearance and behavior, related to composition and variability, formed the characteristic profile. Thus he was of ten able to predict other qualities invisible to the naked eye, such as a percentage of fluorine or other mineral components. These granite individuals were grouped into four families, which also were groups of different relative age that occupy special places in the evolution of the crustal sector.

To learn more about these individual characteristics, Sedenolm studied special textures: orbicular, spotted, and nodular granites and the rapakivi (1928). His paper on “synantectic” minerals (1916) was representative of work on the component material of the rocks. Here his main aim was to establish the sequence of events, and the phenomena of synantectic minerals are a good example. The interfaces of two adjacent minerals, formed in stable association, can begin to produce new minerals by interaction of the primary minerals; in this way two, and sometimes more, stages are marked in the evolution of the rock, characterized by different physicochemical conditions. More interested in transformations than in phase equilibriums, Sederholm noted the results of laboratory experiments but could hardly consider them final criteria. For him, they were useful only insofar as they could be integrated within the organic interdependence of different levels of apprehension.

In this way a spectrum of new methods of observation and interpretations, each set adapted to its own level, was created; it produced a hitherto unsuspected picture of curstal evolution in a historical perspective. Those accustomed to a taxonomic approach found it difficult to accept this manner of reasoning, which was unusual at the beginning of the twentieth century; and it became necessary to reply to the vigorous opposition.

Most of the old crystalline basements are more or less peneplained with low relief, and it was considered impossible to distinguish three-dimensional structures of higher orders of magnitude. Fortunately for Sederholm, a young Swiss geologist, C. E. Wegamann, appeared and showed how to obtain a three-dimensional interpretation, how to reconstruct ancient mountain chains with their different axial culminations and depressions, and how to discover the movements that they had undergone. The former belts became orogens with visible cross sections that were many kilometers in depth. Although in his sixties, Sederholm was still so open-minded and eager to complete his work that he became an ardent student of structural methods, even though their results contradicted some of his former hypotheses. On the other hand, they offered further evidence against the theory of the ubiquity of folding and furnished new conceptual tools for uniformitarian reconstruction.

Sederholm’s outstanding scientific achievements brought him many honors and medals, and the respect accorded him was turned to the welfare of his native land. In 1906 he became a member of the Diet, representing the third estate. An active member of the Workers Institution, he lectured on scientific and other topics and was the author of semipopular and popular articles, papers, and books, on social questions as well as earth sciences. He was a founder of the Geographical Society of Finland and served five times as president, and was one of the most active members of the editorial staff of the Atlas of Finland (1899–1925). With the establishment of the Republic of Finland in July 1919, Sederholm was entrusted with several important missions to the League of Nations,including that concerning the issue of whether the Aland Islands should be Swedish or Finnish. The League also appointed him a member of the Commission for the Independence of Albania. He made two journeys to that country to inspect its frontiers. Unarmed and without military escort, he met the Serbian guerrillas and arranged for their peaceful withdrawal.

Sederholm directed much attention to economic questions, not only economic geology but also general problems. As a member, and twice chairman, of the Economic Society of Finland, he delivered several lectures, one of them on the reasons for North American industrial supremacy (1905). F. W. Taylor’s system of scientific management interested him deeply, probably because of its multileveled reasoning, and in 1915 Sederholm published a noted monograph entitled Arbetets vetenskap (“The Science of Work”).

Sederholm was greatly interested in America, first in the Precambrian shield and its chronology, but also in the politics, economics, industry, social conditions, hospitals, and many other facets of the nation’s life. He traveled several times in Canada and the United States on lecture tours, accepting honors (including the Penrose Medal, in 1928), visiting important outcrops, collecting documents, and observing general conditions. He particularly enjoyed recalling his discussions with N. L. Bowen, the foremost leader of the diametrically opposed magmatist school of petrology. This great scientist admitted that many of the phenomena described by Sederholm were inexplicable by his own theory—in sharp contrast with other petrologists, who simply denied the possibility that they had occurred. One of Sederholm’s favorite projects was a book on America for Europeans, to have been entitled The Country of Broadbingnag. But after retiring, so many matters awaited completion that the time left him too limited to reap the entire harvest on the land he had lilled.


I. Original Works. There is a bibliography of all Sederholm’s main geological publications and a selection of his more important nongeological work in Sederholm’s Selected Works (New York, 1967), 589–594.

His earlier writings include “Über die finnländischen Rapakiwigesteine,” in Tschermaks mineralogische und petrographische Mitteilungen, 12 (1891), 1–31; “Studien über archäische Eruptivgesteine aus dem südwestlichen Finnland,” ibid., “Om bärggrunden i södra Finland. Deutsches Referat,” in Fennia, 8 , no. 3 (1893), 1–137; “Les excurisions en Finlande,” in Guide du VII Congrès géologique international, XIII (St. Petersburg, 1897), 1–22, written with W. Ramsay; “Übereine archä’ische Sedimentformation im südwestlichen Finnland und ihre Bedeutung für die Erklärung der Entstehungsweise des Grundgebirges,” in Bulletin de la Commission géologique de la Finlande, 6 (1889); “Über die Entstehung des Urgebirges,” in Förhandlingar vid Nordiska Naturforskare och läkaremöter (Helsink) (7 July 1902), 88–109; “Über den gegenwärtigen Stand unserer Kenntnis der kristallinischen Schiefer von Finnland,” in Comptes rendus du IX Congrès géologique international (Vienna, 1903), 609–630; “Om granit ochgneis, deras uppkomst, uppträdande och utbredning inom urberget i Fennoskandia,” in Bulletin de la Commission gé de la Finlande, 23 (1907); and “Einige Probleme der präkambrischem Geologie von Fennoskandia,” in Geologische Rundschau, 1 (1910), 126–135.

Subsequent works include “Om palingenesen i den sydfinska skärgården samt den finska urbergsindelningen,” in Geologiska föreningens i Stockholm förhandlingar, 34 (1912), 285–316; “sur les vestiges de la vie dans les formations proterozoiques,” in Comptes rendus du XI Congrès géologique international (1912), 515–523; “Die regionale Umschemlzung (Anatexis) erläutert an typischen Beispielen,” ibid., 573–586; “Subdivion of the Pre-Cambrian of Fennoscandia,” ibid., 683–698; “Hutton och Werner,” in Festskrift tillägnad Edvard Westermarck (Helsinki, 1912), 279–291; “Über ptygmatische Faltungen,” in Neues Jahrbuch für Mineralogie, Geologie und Paläontologie, supp. 35 (1913), 491–512; “Über die Entstehung der migmatitischen Gesteine,” in Geologische Rundschau, 4 (1913), 174–185; “On Regional Granitization or Anatexis,” in Comptes rendus du XII Conreès géologique international (Toronoto, 1913), 319–324; Arbetets vetenskap (“The Science of Work”; 1915); “Different Types of Pre-Cambrian Unconformities,” ibid., 313–318; “On Synantectic Minerals and Related Phenomena,” in Bulletin de la Commission géologique de la Finlande, 48 (1916); “On Migmatites and Associated Pre-Cambrian Rocks of Southwestern Finland, I : The Pellinge Region,” ibid., 58 (1923); “The Average Composition of the Earth’s Crust in Finland,” ibid,. 70 (1925), also in Fennia, 45 , no. 18 (1925), 1–20; “On Migmatites and Associated Pre-Cambrian Rocks of Southwestern Finland. II : The Region Around the Barösundsfjärd West of Helsingfors and Neighbouring Areas,” ibid,. 77 (1926); “On Orbicular Granites, Spotted and Nodular Granites and the Rapakivi Texture,” ibid., 83 (1928); “On Migmatites and Associated Pre-Cambrian Rocks of Southwestern Finland. III : The Aland Islands,” ibid., 107 (1934); and “Ultrametamorphism and Anatexis,” in Pan-American Geologist, 61 (1934), 241–250.

II. Secondary Literature. See Pentti Eskola, “Outline of Sederholm’s Life and Work,” in Sederholm’s Selected Works (New York. 1967), 577–594, with portrait and bibliography; Victor Hackman, “Jakob Johannes Sederholm,” Bulletin de la Commission géologique de la Finlande, no. 117 (1935), with portrait and bibliography; Hans Hausen, “J. J. Sederholm,” in Svenska folkskolans vänners kalender (1934), 151–159, with two portraits; and Hans Hausen, The History of Geology and Mineralogy in Finland, 1828–1918 (Helsinki, 1968), with bibliography; Aarne Laitakari, “Geologische Bibliographie Finnlands 1555–1933,” Bulletin de la Commission géologique de la Finlande, no 108 (1934); and Väinö Tanner, Jakob Johannes Sederholm (Helsinki, 1937), read to the Swedish Academy of Technical Sciences in Finland on 22 Mar. 1935.

Eugene Wegmann

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