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One hundred years of continental drift: the early Italian reaction to Wegener’s ‘visionary’ theory
Abstract
One hundred years ago in 1915 ‘Die Entstehung der Kontinente und Ozeane’ by Alfred Wegener was published, destined to become one of the most controversial geological opus in the first half of the twentieth century. Wegener is the first to combine the most diverse geological (sensu lato) evidences in a single great synthesis. Nonetheless, apart from few upholders, the initial reaction to the drift hypothesis was fierce opposition, and the strongest criticism came from geophysics, the same discipline that, paradoxically, starting from the 1950s led to the Plate Tectonics revolution and, ultimately, to a complete re-evaluation of Wegener’s hypothesis. In the present paper we discuss the initial reaction of Italian scientists to the original continental drift theory, with particular focus on the period between the two world wars. Italian geologists like Fossa-Mancini and Gortani were almost favourable to the new theory, while authors such as Vardabasso and Sacco were neutral or even hostile to the new hypothesis, so iconoclastic for the widely accepted fixist vision of the time. In any case, all these scientists agreed that the new theory had great potential for reopening an enthusiastic debate on issues that were given as established paradigms – the genuine way for progress in science.
... He first thought of the continental drift hypothesis by noticing that the different large landmasses of the Earth almost fitted together similar to a jigsaw puzzle. It was the jigsaw puzzle-like landmasses of the Earth that inspired him to raise research ideas and guided him to verify this hypothesis through many repeated experiments and scientific arguments with his colleagues (Romano et al. 2017). On the other hand, inventions in fields of technologies and engineering of a design nature had their roots in simulation in the real world (Magana 2017;Xie et al. 2018). ...
Spatial ability is a powerful systematic source of individual differences in the areas of science, technology, engineering, and technology (STEM). Abundant research has evidenced that psychometrically assessed spatial ability is a strong predictor of STEM achievement. However, its underlying cognitive process and relevant role in STEM education are unknown. From the perspective of cognitive neuroscience, spatial ability is also considered a human intelligence deriving from the cognitive processing of spatial information in the brain. With the help of the cognitive neuroscience paradigm of spatial navigation, in the present work, we investigate the spatial cognitive process among STEM students and its role in STEM education. A total of 172 undergraduates majoring in veterinary science participated in a spatial navigation test. Participants attempted to return a toy to its original place in an arena when given either internal self-motion cues only, external landmark cues only, or both in a spatial navigation task. Modelling analysis of 172 participants’ spatial navigation behaviours showed that all the participants’ spatial cognitive processes featured navigation cue integration. The results of the different tests showed that students with higher levels of navigation cue integration had better academic performance in STEM learning. The results also indicated that, surprisingly, better academic performance in science and mathematics relied more on the use of internal self-motion cues, while better academic performance in engineering and technology relied more on the use of external landmark cues. This study sheds some light on the spatial cognitive process and its role in STEM education from the cognitive neuroscience perspective, thus deepening the functional understanding of spatial ability as a systemic source of individual differences for STEM education, and provides an empirical reference point for interdisciplinary studies on the role of cognition in the context of STEM education. Implications on STEM learning design and STEM teaching were discussed.
... About 50 years after Croll's contributions, Milutin Milankovitch began working on his orbital theory of paleoclimate, which differed greatly from the ealier theories proposed by Adhémar and Croll in the use, for the first time, of accurate mathematical calculations on the effect of orbital conditional insolation variations at the upper atmospheric boundary. The concept of climatic cycles proposed by the Serbian scientist (Fig. 3) was so revolutionary that it was of comparable scope to the theory of continental drift which had been proposed a few years earlier by the leading German explorer, geophysicist, and meteorologist Alfred Wegener (Miller, 1985;Romano & Cifelli, 2015a, 2015bRomano et al., 2017). It is no coincidence that from 1924 the two great scientists began a collaboration, together with the German meteorologist Vladimir Köppen (Wegener's father-in-law), to understand possible mechanisms to explain the ice ages. ...
One hundred years ago the Serbian engineer, mathematician and geophysicist Milutin Milanković published the seminal work "Mathematical Theory of Thermal Phenomena Caused by Solar Radiation", which laid the foundation for mathematical modelling of climatic cycles. Milanković succeeded in linking major climate change to three known astronomical parameters which controlled the amount of solar radiation on Earth during different seasons and at different latitudes, these are: Earth's orbit eccentricity around the Sun; the tilt or obliquity of Earth's axis of rotation; and the precession of the rotation axis or 'wobblelike' movement. The proposal of periodic fluctuations in Earth's climate (now known as Milanković cycles) was rejected and ridiculed during the 1950s, but received acclaim in the seventies following publication of the outcomes of seminal multidisciplinary research by Hays, Imbrie and Shackleton.
... In conclusione, Alberti stupisce anche per la concezione veramente moderna rispetto ai tempi di un pianeta dinamico in continua evoluzione. Una concezione mobilista della Terra che sarà pienamente afferrata solo nella seconda metà del ventesimo secolo, portando a un vero e proprio cambio di paradigma (Hurley, 1974;Bosellini, 1978;Romano & Cifelli, 2015a, 2015bRomano et al., 2016b). La visione mobilista con evoluzione del paesaggio è stata in parte sicuramente presa in prestito dal maestro Aristotele, come indicato da questa citazione letterale riportata dall'Alberti: "Aristotile dice che il moto de le cose è continuo, e che in processo di tempo avverrà che il mare si scambierà di luogo con i monti, di qui disse colui: "Ciò ch'è sotterra in processo di tempo, Si scoprirà palese, e verrà fuori, E le cose scoperte andran sotterra" (citazione originale di Aristotele non in corsivo; ibid., p. 377). ...
The geological elements found in the De re aedificatoria by Leon
Battista Alberti are discussed for the first time in detail. In Alberti
we find the enlightened conception of how architectural works must
be conceived to adapt to natural processes and their evolution, and
not vice versa. The great architect uses, in a first place, a purely
pragmatic approach to geological knowledge. Noteworthy elements
are the detailed study of historical earthquakes to get an idea of
‘seismic hazard’ characterizing a specific area, a deep understanding
of the evolution of river systems, the use of wells to investigate
the composition of the terrains in the underground to build solid
foundation. These pragmatic elements are also accompanied by more
theoretical interpretations, including very interesting reasoning about
diagenesis, and on sedimentological aspects such as gradation, events
of flooding and fluvial deposition, and river systems progradation due
to the secular sediment supply. In his scientific interpretations, and
in the new proposed vision of art, Alberti manages to reconcile in a
harmonious way the innovations made by Brunelleschi, Masaccio and
Donatello, fully embodying the spirit of the Florentine Renaissance,
where art presupposes a profound understanding of nature and not its
simple imitation in artist works.
... Tra questi vanno sicuramente considerati il rifiuto del diluvialismo imperante, confutandolo con dati diretti osservati in campagna (e non basandosi su ipotesi astruse ricostruite a tavolino e sradicate dal dato fenomenico); i ragionamenti propriamente attualistici utilizzati nelle confutazioni (Romano, 2018b); i primi semi netti di uniformitarianismo metodologico (sensu Gould, 1965;Romano, 2015bRomano, , 2018b; il concetto di un Pianeta dinamico, dove non è il mare a dover salire per portare i fossili sulle più alte montagne, ma sono le montagne stesse a emergere e sollevarsi dai fondi marini. Un problema fondamentale delle scienze geologiche, che sarà risolto in pieno nella sua complessità solamente con la rivoluzione della tettonica delle placche, a partire dalla fine degli anni settanta del ventesimo secolo (Hallam, 1974;Dietz & Holden, 1974;Hurley, 1974;Bosellini, 1978;Romano & Cifelli, 2015a, 2015bRomano et al., 2016). ...
Among historians of geology, the end of the seventeenth century is
well known for the appearance of many detailed theories of the Earth
which attempted to achieve great syntheses of natural processes and
phenomena in order to explain the evolution of the Planet from its
original state to the one that could be observed in the field. Among the
most famous hypotheses are those advanced by English authors such
as Burnet, Ray, Warren, Whiston, and Woodward. These theories met
great success on the European continent, and Italy was no exception:
here, Woodward’s hypotheses were followed by the so-called School of
Bologna, and strongly supported by important authors like Giuseppe
Monti. However, it is exactly from the Italian peninsula that the most
detailed and organic criticism to these theories of the Earth arose.
This paper focuses on the confutation made by Anton Lazzaro Moro:
in his work “De’ Crostacei e degli altri marini corpi che si truovano su’
monti”, the Italian Abbot and naturalist reported the main hypotheses
advanced by Burnet and Woodward, which he criticized and refuted.
Significantly, Moro’s argument relied on the observation of geological
outcrops in the field, where empirical evidence led him to reject the
great syntheses proposed by British authors. Moro’s work reveals a
remarkable awareness of the existence of a uniformity in natural laws:
from this point of view, his thought bears a significant resemblance
with the uniformitarian theories expressed by many naturalists in the
following centuries.
... Probabilmente il Professor Accordi sorriderebbe nel vedersi esso stesso parte della gloriosa storia della nostra disciplina, che tanto lo appassionò sul finire della sua intensa carriera, tenendo il filo che si dipana per secoli da Ristoro d'Arezzo a Raimondo Selli e agli altri scienziati italiani che contribuirono all'affermazione della teoria tettonica globale a partire dagli anni '60 del secolo scorso (si veda Romano et al., 2017). Possiamo però asserire senza timori che la figura di Bruno Accordi si staglia, al pari dei suoi predecessori dei secoli andati, nel Pantheon della Geologia italiana. ...
Nel 2016 ricorreva il centenario della nascita di Bruno Accordi,
figura centrale per geologia romana e italiana a partire dalla seconda
metà del secolo scorso. Tra i diversi contributi e materie analizzate
in una lunga carriera ‘vecchio stampo’, realmente caleidoscopica
e onnivora, Accordi ha avuto anche il merito di aver rilanciato per
primo l’interesse per le radici identitarie delle nostre discipline in
Italia. A partire dagli anni sessanta del secolo scorso, Accordi ha
pubblicato sistematicamente sulla rivista Geologica Romana, giornale
da egli stesso fondato nel 1962 per rendere noti i nuovi progressi fatti
nello studio dell’Appennino, numerosi contributi su figure italiane
centrali per il primo avanzamento delle Scienze della Terra sensu lato.
Il presente contributo vuole essere un tributo al grande geologo e alla
sua opera in campo della Storia della Scienza, che lo vide impegnato
e appassionato negli ultimi anni di vita, lasciando un esempio da
seguire e solide fondamenta per studi futuri in materia.
... Dopo queste intuizioni isolate e quasi estemporanee, a partire dagli anni settanta del secolo scorso, in un periodo di grande fermento per le Scienze della Terra (e.g. Bosellini 1978;Miller 1985;Romano & Cifelli 2015a, 2015bRomano et al. 2016), la letteratura conta un numero decisamente più consistente di contributi su questo tema (e.g. Lamb 1970;Taylor et al. 1980;Kelly & Sear 1984;Mass & Portman 1989). ...
Understanding the relationships between extensive geological phenomena and short and longterm
meteorological manifestations is a scientific achievement that can only be traced back to the
seventies of the twenty century. Despite this, the direct or indirect effects of particularly significant
geological events did not escape the observers of the past and often had repercussions on beliefs,
folklore, artistic and literary works. The present contribution is based on manuscripts and news
recorded between the eighteenth and nineteenth centuries that highlight anomalous meteorological
effects likely connected to intense volcanic activity. Among these, the “strange atmospheric
anomalies” recorded in the meteorological diary of the physicist Giuseppe Bonfioli in 1821, quite
similar to those occurred in 1783 in connection with the eruption of Laki.
... Both objectives would be achieved, Italy proving competitive in various research sectors, as well as Earth Sciences. Significant contributions were made to the new theory of Global Tectonics (see Romano et al., 2017), while contributions made to mitigate natural risks were to prove original. city closest to Rome; and like Greece it was for the ancient world the nursery of culture. ...
With the Industrial Revolution the laws of physics were introduced
to explain natural phenomena. At that time the Vesuvian Observatory
emerged as the first volcanological observatory in the world
to monitor the activity of Vesuvius on a permanent basis. Naples became
an attractor for scholars, who were to analyze volcanic phenomena
by developing relationships between the science of laws and those
of processes. After World War I interest in Naples-based volcanology
further increases, as attested by the founding in the city of Immanuel
Friedlaender’s International Institute of Volcanology. Following the
twenty-year Fascist period, Italy had two objectives: to reconstruct the
network of science laboratories and rebuild the approach to studying
Earth Sciences through comparison with more advanced countries.
Significant and original contributions were made regarding the new
theory of global tectonics and the mitigation of natural risks.
KEY WORDS: Docta Neapolis, Osservatorio Vesuviano, Serapeo,
Deep Time, Science of laws, Sciences of processes.
... His interest in the work of Pilla ( loViSato, 1905) is proven by a speech delivered in 1874 for the commemoration of the Molisan scientist, published posthumously (FoSSa manCini, 1924a), where-among other subjects-he formulated his personal theory of continental drift, talking about a single landmass, then split off into smaller masses, and based on the correspondence of the Atlantic coasts of Africa and America. In a sense, this speech can be considered as an anticipation of the first public exposition of the theory of continental Drift by Wegener ( FoSSa manCini, 1924a;giannitraPani, 1957;lo monaCo, 1983;romano et 1 the royal Geological committee was established in 1867 to coordinate the project of the Geological Map of Italy ( Pantaloni et alii, 2016b). Ital. ...
Celebrating the centennial of Domenico Lovisato's death (1842-1916), this paper highlights the role played by this eminent Italian geologist as a pioneer for the geological knowledge of Calabria region (Southern Italy), a geologically complex area which became the subject of a long-lasting and still continuing debate. Lovisato spent only few years in Calabria (1876-1878) teaching as high school professor of mathematics; this period marked a turning point for his scientific growth representing a switch for his career from avocational to full-time geologist. This experience granted him the involvement in the academic career, with the enrollment in the University of Sassari and Cagliari as Professor of Mineralogy and Geology (from 1878 until his death, in 1916). Lovisato must be acknowledged as the author of the first 1:50,000 geological map of the Calabria region. As such, he should be mentioned for his ethic approach towards environment, anticipating the catastrophic effect of natural phenomena and the modern concepts of geoethic.
... An exception in this respect is represented in part by the work of Moro, where there seems to be present a directional idea of the evolution of the planet: the marine deposits, as a result of different processes, can 'be raised' in some way up to form hills or true mountain ranges, leading to a 'contorted' appearance of the sedimentary strata. This was an essential milestone for the Earth Sciences which would be brought to completion by Hutton, implemented by Lyell in the nineteenth century and understood in its entirety and complexity only in very recent times, with the major interpretative revolution of plate tectonics (see Le Pichon, 1968;Dietz and Holden, 1974;Bosellini, 1978;Miller, 1985;Cifelli, 2015b, 2015c;Romano et al., 2016b). ...
As early as the thirteenth century naturalists of the Italian panorama began to look for a possible explanation for fossils found on emerged land. From the beginning, they tended quite naturally to resort to a catastrophic phenomenon, which found a direct ‘confirmation’ in the Holy Scriptures: the Great Flood. As an element found in numerous peoples, from the Babylonians, to ancient Egypt and the Chinese culture, the Flood became for a long time the only process able to explain the presence of marine fossils on the highest mountains, in a period dominated by a static concept of planet Earth. On the Italian scene, the supporters of the Flood were quite numerous, but equally numerous were the authors who brought evidence against the Deluge hypothesis, preferring a long stationing of the sea in places where the fossils are found today. An influential part of the second group is represented by the glorious Tuscan school that, starting from Boccaccio, includes prominent figures as Leonardo da Vinci, Baldassarri, Bastiani, Giovanni Targioni Tozzetti, Caluri, and Matani. In any case, the aspect that characterizes the majority of Italian authors from both the two interpretative factions, is a predilection to the study of deposits and fossils directly in the field, rather than the construction of ‘big systems’ simply based on the authority of sacred texts or other ancient authors.
... The current absence of such large quadrupeds where large fossil bones are found was used as an element in favor of the giants, in a time when there was still no idea of the great climate change, and paleobiogeographical changes over time. On the other hand, the structure of the continents and the sea was regarded with a fixist view for at least another two centuries, considering that the bold theory proposed by Wegener on plate tectonics was accepted by the entire scientific community only in the 1970s (see Ippolito 1974;Bosellini 1978;Miller 1985;Romano & Cifelli 2015a, 2015bRomano et al. 2016). ...
The myth of giants as first inhabitants of countries is a common legend shared by different cultures. In this paper, we highlight that one of the determining factors of the origination of the myth was the discovery of large vertebrate bones (largely Cenozoic), initially interpreted as the remains of giant humans. Thus, huge skeletons were interpreted by authoritative writers such as Strabo, Philostratus and Pliny (just to name a few) as the bodies of the mythological giant Antaeus, Ilio son of Hercules, Orestes, Cyclops and many others. As for the myth of the Great Flood, also the hypothesis of the giants found a convenient literal confirmation in the Sacred Scriptures. One of the first correct interpretations takes place in the first half of the eighteenth century with the studies of Hans Sloane which applied some rudiments of comparative anatomy to prove that the bones belonged to large cetaceans or terrestrial quadrupeds. In the Italian panorama, until the eighteenth century, several authors were convinced of the past existence of entire nations of giants, which represented the first populations of Mediterranean islands. Sloane’s work had a great impact also in Italy, although some ‘sacs of resistance’ persisted up to mid-nineteenth century.
... This thought anticipated by some three centuries the assumptions explained by the theory of Continental Drift developed by Wegener in 1915 (see Romano & Cifelli 2015a, b;Romano et al. 2017). The treatise 'De subtilitate' was a great scientific success but was fiercely opposed by the orthodox Catholics to whom Cardano replied with his 'Apologia adversus calumniatorem'. ...
Italian physicians have been interested in geology since the fifteenth century or earlier, with leading figures carrying out fundamental and enlightening studies in both fields of competence. Refined cultured men including Bernardino Ramazzini, Antonio Vallisneri, Tommaso Antonio Catullo, Carlo Gemmellaro, Leopoldo Pilla, Giuseppe Meneghini, Gaetano Giorgio Gemmellaro and Arcangelo Scacchi, in addition to the introduction of reasoning and basic concepts for the advancement of Earth sciences, conducted major studies in the medical field, proving once again the holistic interests of Italian intellectuals.
Following the publication of Principles of Geology by Charles Lyell, some scientists were fascinated by the geosciences, carrying out both medical observations and geological studies, and contributing significantly to the development of modern geology. The biographies and works of some leading Italian physicians illustrate their scientific activity in the study of stratigraphy, geomorphology, palaeontology and volcanology, with acknowledgement internationally. These Italian scientists contributed to the political unification of Italy, actively participating in scientific and political discussion, and fulfilling government aims. They contributed to the foundation of the Geological Society of Italy, one of the oldest scientific fellowships in Italy.
... The latter hypothesis has important implications, such as the assumption that the climate was different in the past and changed several times in the course of millennia. Concepts such as glacial and interglacial periods, as well as plate tectonics were still far from being understood or just conceptualised (Bosellini 1978;Miller 1985;Romano & Cifelli 2015a, 2015bRomano et al. 2017). The amount of implications behind the mere intriguing curiosity generated by the discovery of any fossil in the past as today, emphasises the fundamental role that fossils played in bringing out the young geological sciences from the early darkness, promoting the acquisition of basic and fundamental concepts that would remain unexplained by solely lithological, petrographical and mineralogical studies. ...
The actual nature of large vertebrate bones found in sedimentary deposits was a intriguing, debated and unanswered issues until the beginning of the nineteenth century. The fossil bones were interpreted in a number of fantastic ways, e.g. as remains of mythological giants, or bones of dragons killed by saints. These unrealistic notions progressively waned as the scientific advance in comparative anatomy allowed to a correct identification of the large bones as elephant remains. As a result, the question arose as the reason why elephants were present in the Italian peninsula (and in many other parts of Eurasia and America), in climatic conditions so different and in regions so far from the territories they inhabit nowadays. The most parsimonious hypothesis that these bones may represent the remains of elephants brought in Italy either by the legendary Carthaginian general Hannibal Barca or by other commanders for military purposes had some success and diffusion even in Italy. This research aims to analyse the reason behind the success of this theory between the sixteenth and nineteenth centuries. The hypothesis, critically examined and confuted by brilliant Italian researchers such as Giovanni Targioni Tozzetti, was supported by several authors until the beginning of the nineteenth centuries.
This contribution analyses the geological elements sensu lato found in the “La composizione del mondo colle sue cascioni” (The composition of the world with its causes) written by Ristoro d’Arezzo at the end of the thirteenth century. In the treatise is possible to find numerous references to ‘geological’ products and processes ranging, from the shape and structure of the Earth, distribution of emerged lands and seas, geomorphology, sedimentology, to earthquakes and meteorological phenomena, formation and erosion of mountains, references
to specific lithotypes and their formation. Most of these phenomena and interpretative hypotheses are essentially inherited from the Meteorologica of the master Aristotle. The Composition of the Word represents an open window
on the ‘scientific’ naturalistic-astronomical knowledge at the end of the thirteenth century, in a crucial stage of rediscovery of Aristotelian hypotheses and of his commentators, representing the foundation ofall the knowledge and advances of the western world. Even if in the opening Book Ristoro rejects the use ofmiracles to explain nature, the author resorts to the central action of the Heaven as the main shaping agent for Earth structure, living beings, mountains, and mines. Furthermore, God is present throughout the text along with the concept of the scala naturae, with humans representing the pinnacle of perfection among living beings. However, Ristoro can be considered among the first ‘disseminators’ of science, presenting in vernacular Italian the theories of ancient thinkers and thus allowing access to this interpretative world to a wider audience. Furthermore, Ristoro did not limit himself to simply report the theories of past authors, but especially with regard to geological processes (mountain formation, explanation of fossils, mineralizations), he provided completely original interpretations which indicate a direct analytical observation of the natural world. The treatise by Ristoro was certainly the basis for authors of
the following centuries with regard to natural phenomena in general and stronomical ones in particular, with influences certainly on contemporary and slightly later authors such as Brunetto Latini and Dante Alighieri.
In education, practical, experiential, or experimental research is usually based on a number of participants from whom we collect data. We contact them and explain their role in the study and ask them to kindly devote their time to us. Our final dataset (data “useful for our research”) is a portion of our data corpus (all data collected). The story we finally print is the one from the dataset purposefully selected from the data corpus. The myriad of reasons given for not including some of our participants’ data in the dataset include the following: participants’ lack of enthusiasm, punctuality, timely delivery of audio recorded data, or data quality. The pandemic outbreak impacted my participants’ lives, workplaces, and studies. Their practicum experience was impacted too, so some of them could not complete their own teaching rounds. As a consequence, they could not provide enough data to analyse in order to answer my research questions. They tried, but it was not possible for some of them. However, all the data collected, my data corpus, is valuable to me as a teacher educator and as a mentor teacher. This is a twofold story: my participants’ troubles and commitment during their practicum, and my own troubles collecting data while not neglecting what my unselected participants did for me. The pandemic’s devastating effects in teacher education programmes in Chile is affecting pre-service teachers’ practicum experience, their relationship with their students and their relationship with their mentor teachers, both university-based tutors and school-based mentors. Knowing the needs and experiences of pre-service teachers who did not get a completed experience in their allocated university-partner schools may help us to better navigate the practicum experience in the present times.
Questions about the origin and dispersal of the coconut palm have remained unsettled for centuries and opinions are still divided today. Two centuries ago an expedition of European naturalists in Brazil favoured a South American origin and dispersal across the Pacific to Asia, presumably by people in small boats. One hundred years after the Brazil expedition coconut oil had become a profitable item of worldwide trade and, for that reason, of interest to science. A strong case was made for a coral island origin. Unfortunately, the detailed account was not written in English and was published in two parts in two years and in a journal that ceased publication for two decades. Our intention is to encourage readers to make a translation of ‘La Culla del Cocco’ and to crowd fund a commemorative centenary before 2023.
The systematic use of fossil and sedimentological characters in palaeoenvironmental, palaeoecological and palaeoclimatic reconstructions is a fairly recent breakthrough of Earth Sciences. Traditionally, the works by James Hutton and Charles Lyell are viewed as true milestones of geology and the first coherent reasoning in the palaeoecologic context, as a necessary result of the new 'doctrine' of actualism. However, the foundation for actualistic reasoning, and their genuine use to interpret the fossil deposits, are clearly found in the writings of Italian naturalists more than four centuries before the publication of The Principles. In this paper, the first seeds of actualistic and palaeoecological reasoning, detectable in the Italian panorama between the thirteenth and early nineteenth century, are discussed. As early as the thirteenth century, authors like Ristoro d'Arezzo used sedimentary processes currently observed to interpret the fossil deposits. Naturalists as Marsili and Donati emphasized the close correspondence between the current seabed, abundance and distribution of species, and the conditions observed in the fossil deposits. Targioni Tozzetti correctly interpreted the remains of large vertebrates in Italy as belonging to animals endemic of the Peninsula, using this evidence to infer a warmer climate in the past and surprising readers of the day with the modernity of his ideas. These great naturalists not only imagined a completely different flora based on the fossil record, but attributed the warmer climate of the past to changes in the sea level, thus providing arguments used by Lyell some eighty years later to explain climate change over geological time.
At the turn of the seventeenth and nineteenth centuries, Earth sciences were in a period of heated debates, with an arduous acquisition of basic principles for geology. Among the unresolved debates, was the well-known between Neptunists and Plutonists, and there was still disagreement between the supporters of a catastrophic flood and a long permanence of the sea in areas currently occupied by emerged lands. In such a climate of uncertainty appears the ‘Theory of the Earth’ of Ermenegildo Pini, an Italian Barnabite cleric. Pini was a many-faceted figure, including naturalist-scientist and technician, with interests ranging from architecture and engineering to natural sciences sensu lato. As a Diluvialist and a Neptunist, Pini strongly rejected the igneous theory – with Earth completely molten in origin – preferring instead one involving a fluidity in water and formation of ‘primary mountains’ due of centrifugal acceleration induced by Earth’s rotation. Alternatively, the so-called ‘transitional’ and ‘secondary’ mountains were entirely attributed to the rapid, catastrophic and universal flood literally interpreted from the Holy Scriptures. Despite his strongly theistic approach to the evolution of our planet, some of the intuitions and methodological approaches of Pini are extremely interesting and worthy of review and renewed discussion.
Chronostratigraphy has a "prehistory" beginning with Leonardo's and Steno's twofold relative geologic time division. It developed further with Marsili's (1728), Lehmann's (1756), Arduino's (1759-60) and Werner's (1787) threefold, fourfold, and fivefold divisions respectively. Meanwhile, the initial steps were being taken in understanding Earth's chronometry. Geological mapping exponentially increased the number of lithostratigraphic and chronostratigraphic units and forced the need for a common language and practice by international agreement. That objective became feasible with the establishment of the International Geological Congress (IGC), and the bipolar or dual classification of chronostratigraphic and chronologic units was formally established during the 2nd IGC in Bologna in 1881. Chronostratigraphic classification has displayed a remarkable nomenclatural stability, notwithstanding continuously changing criteria of use, correlation, improvement, and redefinition of the standard chronostratigraphic units. The development of chronostratigraphy was by scientific research and the necessary stability was through the IGC, as it appears from this review of the main chronostratigraphic resolutions and recommendations adopted by the IGC sessions from Bologna in 1881 to Sydney in 1976. An hierarchical classification and an historical approach underpin the evolution of chronostratigraphic classification. Five stages of evolution are outlined. Their succession illustrates changing paradigms, ongoing improvement by new tools of correlation, and the stability of names defined and used in a permanent common language. This flexibility should guide future developments in chronostratigraphy.
Although the popular map by William Smith “A Delineation of the Strata of England and Wales
with Part of Scotland” is properly celebrated as the first complete geological map of an entire
country, the basic principles used by the famous English canal surveyor were epistemologically
founded and utilized by the Italian Count Luigi Ferdinando Marsili about a century earlier. Marsili,
“uomo d’arme e scienza” (“man of army and science”), represents a vitally important pioneer in the
fields of geography, cartography, and oceanography, with farther-ranging knowledge that included,
for example, the field of archaeological survey. With his geologic map of the Cesenate sulphur
mines Marsili was the first geologist to make the quantum leap from simple mineralogical maps —
which report the location and access of mines on a topographic background— to a proto-geological
map, wherein the areas represented by corresponding lithostratigraphic units are delimited. If
Smith’s map is rightly regarded as an ambitious work for the areal extent covered, Marsili’s
“Treatise on the Structure of the Earthy Globe” (lamentably unfinished) was by far more ambitious.
The 200 sheets that come down to us include about 50 pen drawings and more than 35 watercolored
plates. These clearly show how the work of Marsili took radical departure from the classic
systems or “Theories of the Earth” espoused by British contemporaries such as Burnet and
Woodward: in the Italian scientist we find the first arguments on the mountain roots and the
observations that, much later, led to the principle of isostasy. In the fields of stratigraphy, regional
geology, oceanography, and geological mapping, Marsili anticipated scholarly thought by at least a
century.
The Italian naturalist Ulisse Aldrovandi (1522-1605) - often reductively considered as a mere encyclopedist and avid collector of natural history curiosities - lived an adventurous youth and a long maturity rich of manuscripts, books, and outstanding achievements. He assembled the largest collections of animals, plants, minerals, and fossil remains of his time, which in 1547 became the basis of the first natural history museum open to the public. Shortly after that, he established the first public scientific library. He also proposed a complete single classification scheme for minerals and for living and fossil organisms, and he defined the modern meaning of the word "geology" in 1603. Aldrovandi tried to bridge the gap between simple collection and modern scientific taxonomy by theorizing a "new science" based on observation, collection, description, careful reproduction, and ordered classification of all natural objects. In an effort to gain an integrated knowledge of all processes occurring on Earth and to derive tangible benefits for humankind, he was a strenuous supporter of team effort, collaboration, and international networking. He anticipated and influenced Galileo Galilei's experimental method and Francis Bacon's utilitarianism, providing also the first attempt to establish the binomial nomenclature for both living and fossil species and introducing the concept of a standard reference or type for each species. His books and manuscripts are outstanding contributions to the classification of geological objects, and to the understanding of natural processes such as lithification and fossilization, thereby also influencing Steno's stratigraphic principles. The importance given to careful observation induced Aldrovandi to implement a unifor-mitarian approach in geology for both the classification of objects and the interpretation of processes. Aldrovandi influenced a school in natural history that reached its climax with the Istituto delle Scienze of Bologna in the seventeenth and eighteenth centuries with scientists such as Cospi, Marsili, Scheuchzer, Vallisneri, Beccari, and Monti in geology, and Malpighi, Cassini, Guglielmini, Montanari, Algarotti in other fields.
The scientific studies of the Italian physician and naturalist Antonio Vallisneri (1661-1730) were concerned with the cultural and religious implications of the debate on fossils in the early decades of the eighteenth century. In De' Corpi Marini he summarized the main diluvial theories but declined to support them. He explained the presence of fossils in strata in mountainous regions as the result of localized multiple flood and emersion sequences, and restricted the direct action of God to the biblical Deluge. This theory clearly contradicted the biblical interpretation provided by Catholic orthodoxy, which affirmed the existence of a single global Deluge. Vallisneri therefore had to gloss over its real meaning and use a careful self-censorship system, a strategy that he frequently used in his books. The comparison with the work of several Italian and European authors had great relevance to Vallisneri's theories. He continually exchanged correspondence and natural objects with some of the most outstanding of the eighteenth century natural philosophers. This involvement with other scholars deeply influenced his thought, and helped him to reach a pre-eminent status in the Italian scientific community of the time.
It is noted that different physicists and geologists have in recent years espoused not less than four groups of theories of the physical behavior of the Earth's interior. Recent observations of submarine geology, heat, and rock magnetism have tended to support some form of continental drift rather than the older concept of a rigid earth.The Hawaiian Islands are one of seven, parallel, linear chains of islands and seamounts in the Pacific Ocean of Tertiary to Recent age. Their nature had previously been explained in terms of a series of volcanoes along parallel faults. Horizontal shear motion along these faults was supposed to be extending them southeasterly.The inadequacies of this explanation are pointed out. If there are convection currents in the Pacific region and if the upper parts of these cells move faster than the central parts, sources of lava within the slower moving cores could give rise to linear chains of progressively older volcanic piles such as the Hawaiian Islands. This view is shown to be compatible with seismic observations and age determinations.
A comprehensive study of the observations of seismology provides widely based support for the new global tectonics founded on the hypotheses of continental drift, sea-floor spreading, transform faults, and underthrusting of the lithosphere at island arcs. At present within the entire field of seismology there appear to be no serious obstacles to the new tectonics. Seismic phenomena are explained, in general, as the result of interactions and other processes at or near the edges of a few large mobile plates of lithosphere that spread apart at the ocean ridges where new surficial materials arise, slide past one another along the large strike-slip faults, and converge at the island arcs and arc-like structures where surficial materials descend. Study of world seismicity shows that most earthquakes are confined to narrow continuous belts that bound large stable areas. In the zones of divergence and strike-slip motion, the activity is moderate and shallow and consistent with the transform fault hypothesis; in the zones of convergence, activity is also at shallow depths but includes intermediate and deep shocks that grossly define the present configuration of the downgoing slabs of lithosphere. Seismic data on focal mechanisms of about 100 widely distributed shocks give relative motions that agree remarkably well with Le Pichon's simplified model in which relative motions of six large and rigid blocks of lithosphere covering the entire earth were determined from magnetic and topographic data associated with the zones of divergence. The lengths of the deep seismic zones appear to be a measure of the amount of underthrusting during approximately the last 10 million years. The presence of volcanism, the generation of many tsunamis (seismic sea waves), and the frequency of occurrence of large earthquakes also seem to be related to underthrusting or rates of underthrusting in island arcs.
The purpose of the present paper is to analyse the geological
elements and references found in Dante Alighieri’s Inferno, which
have never been treated in complete and comprehensive manner.
Dante used wisely and in a unique manner the elements of nature,
especially of landscape, to build the material foundation on which
the fiction of the underworld journey is based. Specific kinds of
rocks, steep cliffs, landslide bodies, lakes of hydrothermal water,
waterfalls, become basic material in the hands of the Florentine
poet, on which to base metaphors and similes.
In Dante’s Inferno there are references to hydrogeology, earthquakes,
mountain structures, deposition of travertine, landscape
modelling, meteorological phenomena, structure of the Earth and of
the entire cosmos. The grandeur and mastery of Dante lies in being
able to communicate, in short lines, the strong separation between
scientific facts of natural phenomena and their use for aesthetic,
poetic, political, and even ethical purposes. In dealing with complex
issues such as the “geophysical equilibrium” and the reason for the
current distribution of land and ocean, Dante does not simply accept
the theories of Aristotle (as stated by several exegetes) but shows a
critical and deep analysis in the field of geology sensu lato, considering
and preferring the phenomenal datum to the abstract theories. The
work of Dante and his contemporaries did not impersonate the
“dark period” for science, as found in many interpretations of the
Middle Ages, but the cultural context where those questions were
posed which served as foundation and propellant for the subsequent
“scientific revolution”.
The digital storage and communication of significant geological data became
increasingly more objective and accessible through the development of new technologies or the
implementation of already well-known techniques as photogrammetry. Digital acquisition of
geometries (both structural and depositional) of significant geological outcrops is deemed
necessary, especially if the site concerned is liable to be damaged or hopelessly involved in natural
processes of geological and geomorphological evolution. In this paper, we tested the performances
of two different open-source software (i.e. VisualSFM and ARC3D) on a small-scale but
paradigmatic outcrop in the Umbria-Marche Apennines (Italy). The test showed that ARC3D
provides an high-resolution model, employing a relatively short time and requiring a not expensive
hardware support for processing hundreds of photos. In the text, 3D models of the selected outcrop
are reported and discussed emphasizing the potential of the method to highlight structural,
sedimentological and paleontological details.
As a result, 3D photogrammetry proved to be a powerful and effective tool to digitally conserve and
objectively communicate important geological observations and to facilitate accessibility and
dissemination of the collected data within the scientific community.
The appearance of magmatic rocks on the surface or near it is the result of a certain chain of processes, a list of which might look like the following: (a) a partial or complete melting of the upper mantle and the formation of a primary magmatic emulsion; (b) rise of the primary magmatic emulsion; (c) isolation of basaltic asthenoliths; (d) rising of asthenoliths; (e) a change in composition of the primary magma as a result of differentiation, assimilation and contamination; (f) heating of the crust, regional metamorphism, melting of rocks of the crust, gneissification and granitization. This paper aims to give a brief survey of the probable nature of the processes mentioned above from the viewpoint of the tectonic environment in which they occur. This is the view of a tectonist concerning magmatism. The survey is confined to the continents.
doi: 10.1080/08912963.2013.879866
As a result of their intrinsic beauty and relative abundance in some Mesozoic deposits, ammonites have always attracted the
attention of scholars and curious people, with written testimonies that can be traced back to Pliny’s Naturalis Historiae of 75
AD. The mysterious and evocative charm enclosed behind these extinct cephalopod has made its influence felt on legends,
myths, necromancy, medicine, religion and literature, attracting the literary interest of authors such as Goethe, Scott, Schiller
and Salgari. Of particular interest is the evolution of scientific thought and interpretations that, over time, have groped to find
a place for these ‘difficult fossils’, suspended between the organic world and the stone. In the present work, I briefly discuss
the history of the study of ammonites in the Italian peninsula, during the period between the sixteenth and the late nineteenth
centuries. Initially interpreted as petrified snakes, and believed for a long time to be ‘giant’ ancestors of living and extinct
foraminifera, only in the nineteenth century, ammonites were definitively interpreted as extinct cephalopods, with the
recognition of their crucial importance for biostratigraphy.
Following the major contributions of Wegener and Argand (Part 1), it was the work of synthesis carried out by R. Staub that represented the major contribution Alpine geology made with respect to that heritage. The research work of young scientists (Gagnebin, Juvet, Wavre, Leuba) who had been influenced by Argand was of lesser importance. Ampferer’s ground breaking contribution, coming along with illuminating graphic illustrations, was all but ignored. Although remaining fairly popular, the theory of continental drift found itself under the heavy fire of criticism from influential geologists in the USA and in Europe. In order to test the validity of the idea, C.E. Wegmann suggested linking geological field work with oceanographic research. He showed that the trajectories of drifting had to be conceived as following the small circles of the sphere. With regard to Alpine geologists of the time, they were renowned for the high quality of their geological mapping. This remained the very special activity in which they excelled, but they focused on topics that were becoming narrower and narrower, and increasingly specialised. The new avenues for research that Holmes and Hess opened up had but little impact on Alpine geologists. In fact, they apparently remained unaware of a note by Holmes written in German and published in a Swiss journal. On the eve of the Second World War, the meeting of the Geologische Vereinigung devoted to the origin of the Atlantic Ocean confirmed that continental drift was being seriously challenged, although a few papers pointed to new developments, e.g. that in Iceland extensional tectonics had been active for the last 5,000 years. Most Alpine geologists were either highly critical of the theory of plate tectonic when it arrived or expressed serious reservations towards the idea. Of the exceptions, first Laubscher and then Bernoulli showed very clearly how important the new theory could be for understanding the evolution of Alpine orogeny. Continental drift and plate tectonics were very much the product of the creative imagination of human minds. Whereas Wegener used a broad range of confirmed results, plate tectonics sprang out of the new research being carried out in the domain of oceans. Graphic illustration was one of the favourite vehicles used to put across these new perspectives. Sometimes their impact remained alive long after their author had withdrawn his backing for the idea (as was the case for Argand’s “embryonic tectonics”); sometimes, even in spite of their very high standard, they were just ignored (which was the case for Ampferer).
The search for the true nature and origin of fossils gave rise, starting about the beginning of the sixteenth century and
throughout the seventeenth century, to a heated debate between the supporters of the inorganic nature of these objects and
proponents of an interpretation of fossils as ex-vivi. Among the latter, a key figure is the Italian painter Agostino Scilla
(1629–1700), who represents one of the first naturalists who was able to accumulate substantial evidence to support the
interpretation of fossils as once-living marine organisms. The world view of Scilla and his real contribution to paleontology
are here analysed and contextualised, taking into account the state of knowledge characterising the time of his activities.
Scilla was not only a pioneer in the field of paleontology, but he prepared the groundwork for the achievement of milestone
geological concepts such as actualism, taphonomy and recognition of internal and external moulds (in the instance of nonrepresentation
of original hard parts); Scilla deserves further recognition as one of the first to attempt sedimentological
interpretation of rocky bodies observed directly in the fiel
A detailed aeromagnetic survey has been made over a large portion of the Reykjanes Ridge. The magnetic pattern observed displays great linearity, parallel to the topographic trend of the ridge and has the topographic crest as an axis of symmetry. The identification of two main magnetic provinces, noted in previous studies of the mid-ocean ridges, is confirmed. Possible relations between the structures of the Icelandic Plateau and the Reykjanes Ridge were investigated.
Oceanic islands increase in age from the mid-ocean ridges towards continents and the andesite line reaching a maximum known age of Upper Jurassic. The Seychelles appear to be a continental fragment. Several pairs of lateral aseismic ridges extend from islands on the mid-ocean ridge to adjacent continents. Their continental junctions mark points on opposite coasts which would also fit if the continents were reassembled according to the criteria used by Wegener. As Holmes has shown each pair of ridges tends to have distinctive chemical characteristics. One possible explanation is that convection currents in the mantle rising along the mid-ocean ridges and sinking beneath trenches have carried the crust apart across the Atlantic, India and East Pacific Oceans. The lateral ridges may be approximately streamlines. Although Darwin showed that most volcanic islands sink, a few have been uplifted. Most of these lie a few hundred kilometres in front of deep trenches, suggesting that they may be on the crest of a standing wave in front of the trenches and that the crust is rigid. Of eleven straight chains of young islands in the Pacific ten get older away from the East Pacific Ridge. They could also be streamlines, fed by lava rising from deep within convection cells with stagnant cores. The regularity of ridges suggests non-turbulent flow.
A reconnaissance survey of the magnetic anomaly pattern over the Indian Ocean is interpreted in terms of the spreading floor hypothesis. The recent movements of the oceanic crustal blocks and of the adjacent continents are deduced from an examination of the axial magnetic pattern over the mid-ocean ridge. An active branch of ridge runs SE-NW from south of Australia to the Gulf of Aden, and the spreading along its axis corresponds to a relative rotation of Africa away from Asia with the pole of rotation centered near 26°N and 21°E. A southwest branch of ridge running from Mauritius to south of Africa has not been the site of measurable spreading since the Mesozoic era. A description of the anomaly pattern over the flanks of the ridge leads to a hypothetical history of the fragmentation of the Gondwana continent.
Taking up ideas suggested by George Basalla, the paper examines some aspects of the early development of geological work in China in the twentieth century, in particular the education and careers of some prominent early Chinese geologists. It is shown that these men received training overseas that could have made them receptive to mobilist ideas. Within China, a number of interesting ‘whole-Earth’ theories were developed, and some account of these is given. The introduction of plate tectonics into China was delayed by the events of the Cultural Revolution, but thereafter the plate tectonic theory was accepted quite rapidly by Chinese geologists, owing to the already-existing mobilist views in China and the lack of a well-established ‘geosyncline theory’ in that country. Recent work in China has deployed Western ideas of plate tectonics, but has synthesized them in an eclectic manner in a number of distinctive Chinese whole-Earth theories. The effect of Russian ‘fixist’ doctrines does not appear to have been very great in China. The study shows that the Basalla model has some utility in the Chinese case, but only in a very general way. Some ideas of Shigeru Nakayama are deployed to account for features of the Chinese geological community and Chinese geological theorizing.
Some studies seem to indicate that age may not be nearly so powerful a factor in structuring scientific disputes as has long been supposed. This paper views the weak and apparently inconsistent empirical associations reported in earlier studies as arising from incomplete analysis of the relationship between age and receptivity to new scientific theories. Explanations as to why age and receptivity might co-vary have focused on motivational factors that reinforce attachments to existing knowledge, overlooking the possibility that the resources which scientists accrue during their careers may well buffer the increased intellectual risk taken in advocating speculative theories. Older scientists may therefore be better positioned than their younger colleagues to speak out earlier in support of new but controversial theories. Age may thus have contradictory effects on receptivity. The hypothesis that the effects of age are mediated by historical changes in prevailing scientific opinion is examined by a quantitative case study of the reception of continental and later plate tectonics theory.
The misconception that Alfred Wegener used the modern-day coastlines for his reconstruction of Pangea has been propagated from his day to the present. A letter written by Wegener to his wife in 1911 demonstrates unequivocally that even before he first began to formulate the hypothesis of continental drift, Wegener did not consider fitting the continents at the present shorelines. Rather, he felt that the match should be made at "the margin of the continental slope in the deep sea." He subsequently retained this concept in all of the editions of his book The Origin of Continents and Oceans.
The history of development of mobilistic ideas in Russia-USSR is reviewed. After the first burst of interest stimulated by Wegener's works, a long period of domination of fixist “reaction” followed. The revival of mobilism in the sixties was expressed mainly in the discovery of the very important role of nappes and wrench-faults in the structure of all the folded systems of the USSR territory. The plate tectonics concept met at the beginning a very strong resistance, but later it gained a fast growing number of supporters and in the last years soviet geologists made a seizable contribution to the development of this concept.
A geometrical model of the surface of the earth is obtained in terms of rigid blocks in relative motion with respect to each other. With this model a simplified but complete and consistent picture of the global pattern of surface motion is given on the basis of data on sea-floor spreading. In particular, the vectors of differential movement in the ‘compressive’ belts are computed. An attempt is made to use this model to obtain a reconstruction of the history of spreading during the Cenozoic era. This history of spreading follows closely one previously advocated to explain the distribution of sediments in the oceans.
The stratigraphical approach and geological mapping of William Smith in England and Georges Cuvier in France gave birth to modern geology. However, before 1815 neither used the word 'geology', a term first coined by Ulisse Aldrovandi in 1603. At the turn of the nineteenth century most leading geoscientists were based in France and Germany, but those in Britain were poised to take over the lead. After three centuries of dominance in science and geology, was Italian geology in decline? A review of the works of Italian geologists and the role these played in disseminating Italian geological research has been undertaken to examine this question. The French Revolution and the Napoleonic wars shocked the Italian states, disrupted the economic order and discontinued the progress of science. Nevertheless, from 1759 to 1859 over 40 classic papers in geology were published in Italy. Among them, Gian Battista Brocchi's Conchiologia Fossile is the most renowned for having inspired Charles Lyell's work. In the middle decades of the nineteenth century Italian geoscientists made up the majority of foreign members of both the French and English geological societies. The Italian Geological Society was not formed until 1881. This was largely due to the earlier political fragmentation of Italy into many small states.
The transform fault concept is extended to a spherical surface. The earth's surface is considered to be made of a number of rigid crustal blocks. It is assumed that each block is bounded by rises (where new surface is formed), trenches or young fold mountains (where surface is being destroyed), and great faults, and that there is no stretching, folding, or distortion of any kind within a given block. On a spherical surface, the motion of one block (over the mantle) relative to another block may then be described by a rotation of one block relative to the other block. This rotation requires three parameters, two to locate the pole of relative rotation and one to specify the magnitude of the angular velocity. If two adjacent blocks have as common boundaries a number of great faults, all of these faults must lie on ‘circles of latitude’ about the pole of relative rotation. The velocity of one block relative to the other must vary along their common boundary; this velocity would have a maximum at the ‘equator’ and would vanish at a pole of relative rotation. The motion of Africa relative to South America is a case for which enough data are available to critically test this hypothesis. The many offsets on the mid-Atlantic ridge appear to be compatible with a pole of relative rotation at 62°N (±5°), 36°W (±2°). The velocity pattern predicted by this choice of pole roughly agrees with the spreading velocities determined from magnetic anomalies. The motion of the Pacific block relative to North America is also examined. The strike of faults from the Gulf of California to Alaska and the angles inferred from earthquake mechanism solutions both imply a pole of relative rotation at 53°N (±3°), 53°W (±5°). The spreading of the Pacific-Antarctic ridge shows the best agreement with this hypothesis. The Antarctic block is found to be moving relative to the Pacific block about a pole at 71°S (±2°), 118°E (±5°) with a maximum spreading rate of 5.7 (±0.2) cm/yr. An estimate of the motion of the Antarctic block relative to Africa is made by assuming closure of the Africa-America-Pacific-Antarctica-Africa circuit and summing the three angular velocity vectors for the cases above.
In his first publication on continental drift, Alfred Wegener anticipated sea-floor spreading, the functional relationship between bathymetry and age or temperature below the sea floor, perhaps mantle convection, and some aspects of plate tectonics. Some of these insights, such as sea-floor spreading and bathymetry with age, did not appear in his later work; others, such as convection and plate tectonics, were taken up when new evidence became available. His intuition led him to these insights, and he had a very clear perception of the distinction between facts and speculation.
It is noted that different physicists and geologists have in recent years espoused not less than four groups of theories of the physical behavior of the Earth’s interior. Recent observations of submarine geology, heat, and rock magnetism have tended to support some form of continental drift rather than the older concept of a rigid earth.The Hawaiian Islands are one of seven, parallel, linear chains of islands and seamounts in the Pacific Ocean of Tertiary to Recent age. Their nature had previously been explained in terms of a series of volcanoes along parallel faults. Horizontal shear motion along these faults was supposed to be extending them southeasterly.The inadequacies of this explanation are pointed out. If there are convection currents in the Pacific region and if the upper parts of these cells move faster than the central parts, sources of lava within the slower moving cores could give rise to linear chains of progressively older volcanic piles such as the Hawaiian Islands. This view is shown to be compatible with seismic observations and age determinations.