Jennifer McElwain.

Interview with Jennifer McElwain, who performs plant experiments in controlled atmospheric, light and climatic conditions at Trinity College Dublin to assess how these factors have influenced plant evolution and ecology throughout Earth's history.

Rapid ocean acidification and protracted Earth system recovery followed the end-Cretaceous Chicxulub impact.

Mass extinction at the Cretaceous-Paleogene (K-Pg) boundary coincides with the Chicxulub bolide impact and also falls within the broader time frame of Deccan trap emplacement. Critically, though, empirical evidence as to how either of these factors could have driven observed extinction patterns and carbon cycle perturbations is still lacking. Here, using boron isotopes in foraminifera, we document a geologically rapid surface-ocean pH drop following the Chicxulub impact, supporting impact-induced ocean acidification as a mechanism for ecological collapse in the marine realm. Subsequently, surface water pH rebounded sharply with the extinction of marine calcifiers and the associated imbalance in the global carbon cycle. Our reconstructed water-column pH gradients, combined with Earth system modeling, indicate that a partial ∼50% reduction in global marine primary productivity is sufficient to explain observed marine carbon isotope patterns at the K-Pg, due to the underlying action of the solubility pump. While primary productivity recovered within a few tens of thousands of years, inefficiency in carbon export to the deep sea lasted much longer. This phased recovery scenario reconciles competing hypotheses previously put forward to explain the K-Pg carbon isotope records, and explains both spatially variable patterns of change in marine productivity across the event and a lack of extinction at the deep sea floor. In sum, we provide insights into the drivers of the last mass extinction, the recovery of marine carbon cycling in a postextinction world, and the way in which marine life imprints its isotopic signal onto the geological record.

La esfera terrestre en el cosmos isabelino: una aproximación a la difusión temprana del copernicanismo en Inglaterra / The terrestrial sphere in the Elizabethan cosmos: an approach to the early spread of Copernicanism in England

Este artículo presenta una lectura de los principales tratados de cosmología publicados en Inglaterra durante la segunda mitad del siglo XVI a partir del concepto de globo terráqueo. Considerando las discusiones en torno a la relación proporcional entre la tierra yel agua, se propone que los primeros autores en mencionar a Copérnico adoptaron la prueba geométrica expuesta en De revolutionibus orbium coelestium (1543), aunque sin citar directamente esta obra. Mientras Robert Recorde describe a grandes rasgos el argumento allí contenido, Thomas Hill reproduce textualmente la explicación del mismo ofrecida por Caspar Peucer ensus Elementa doctrinae de circulis coelestibus, et primo motu (1551). La presencia de la prueba matemática en favor del globo terráqueo, tiende a desaparecer en la medida que la teoría de la proporción décupla pierde relevancia hacia finales del siglo XVI (AU)

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El 'Mundus Subterraneus' de Juan Ignacio Molina o el Geólogo como economista / The 'Mundus Subterraneus' Juan Ignacio Molina or the geologist gives as economist

En general, la obra del ex jesuita chileno Juan Ignacio Molina (1740-1829) no ha sido estudiada con profundidad a la luz de la historia de la geología. Este artículo reconstruye el origen y la morfología de parte de las ideas que el naturalista chileno elaboró sobre la estructura interna de la Tierra. Se verá cómo las ideas geológicas desarrolladas por Molina fueron más allá de la simple reflexión científica. El desarrollo de una disciplina particular y novedosa como la economía política, también influyó en el tipo de reflexiones que Juan Ignacio Molina desarrolló sobre la organización interior de la Tierra, los procesos geológicos y las descripciones sobre la naturaleza del Reino de Chile a fines del siglo XVIII (AU)

In general, the work of the Chilean ex Jesuit Juan Ignacio Molina (1740-1829) has not been studied under the light of history of geology. This article attempts to reconstruct the origin and morphology of the ideas in which the Chilean naturalist developed about the internal structure of the Earth. We will see how the geological ideas elaborated by Molina went beyond the scientific reflection. The development of a particular discipline as political economy during the eighteenth century also influenced Juan Ignacio Molina ́s thoughts about the internal organization of the Earth, geological processes and the descriptions of the nature of Chilean kingdom in the late eighteenth century (AU)

'One physical system': Tansley's ecosystem as Earth's critical zone.

Integrative concepts of the biosphere, ecosystem, biogeocenosis and, recently, Earth's critical zone embrace scientific disciplines that link matter, energy and organisms in a systems-level understanding of our remarkable planet. Here, we assert the congruence of Tansley's (1935) venerable ecosystem concept of 'one physical system' with Earth science's critical zone. Ecosystems and critical zones are congruent across spatial-temporal scales from vegetation-clad weathering profiles and hillslopes, small catchments, landscapes, river basins, continents, to Earth's whole terrestrial surface. What may be less obvious is congruence in the vertical dimension. We use ecosystem metabolism to argue that full accounting of photosynthetically fixed carbon includes respiratory CO2 and carbonic acid that propagate to the base of the critical zone itself. Although a small fraction of respiration, the downward diffusion of CO2 helps determine rates of soil formation and, ultimately, ecosystem evolution and resilience. Because life in the upper portions of terrestrial ecosystems significantly affects biogeochemistry throughout weathering profiles, the lower boundaries of most terrestrial ecosystems have been demarcated at depths too shallow to permit a complete understanding of ecosystem structure and function. Opportunities abound to explore connections between upper and lower components of critical-zone ecosystems, between soils and streams in watersheds, and between plant-derived CO2 and deep microbial communities and mineral weathering.

Darwin and the geological controversies over the steady-state worldview in the 1830s.

In the first part of this paper, I will show that although Darwin's geological works only covered the first years of his scientific career, these played a non-negligible role in the earth sciences of the mid-nineteenth century. His intellectual proximity with Charles Lyell often made him his disciple. This is indeed the case with respect to debates over 'gradual' soil movements and 'catastrophic' soil movements, and for 'steady-state' cycles as opposed to 'directionalistic' ones. This being said, it is also true that in South America Darwin saw geological processes which were incompatible with Lyell's explanations. It must therefore be recognized that Darwin held a middle-of-the-road position between uniformitarianism (Lyell) and catastrophism (Humbolt and von Buch), at least as far as some geological questions were concerned. In the second part of the paper, debates on geological issues during Darwin's active years will be put in the methodological context of the Scientific Revolution of the seventeenth century.

'A thorn in the side of European geodesy': measuring Paris-Greenwich longitude by electric telegraph.

The difference in longitude between the observatories of Paris and Greenwich was long of fundamental importance to geodesy, navigation and timekeeping. Measured many times and by many different means since the seventeenth century, the preferred method of the later nineteenth and early twentieth centuries made use of the electric telegraph. I describe here for the first time the four Paris-Greenwich telegraphic longitude determinations made between 1854 and 1902. Despite contemporary faith in the new technique, the first was soon found to be inaccurate; the second was a failure, ending in Anglo-French dispute over whose result was to be trusted; the third failed in exactly the same way; and when eventually the fourth was presented as a success, the evidence for that success was far from clear-cut. I use this as a case study in precision measurement, showing how mutual grounding between different measurement techniques, in the search for agreement between them, was an important force for change and improvement. I also show that better precision had more to do with the gradually improving methods of astronomical, time determination than with the singular innovation of the telegraph, thus emphasizing the importance of what have been described as 'observatory techniques' to nineteenth-century practices of precision measurement.

[Inventories of the Earth. Mineral resource appraisals and the rise of resource economics]. / Inventuren der Erde. Vorratsschätzungen für mineralische Rohstoffe und die Etablierung der Ressourcenökonomie.

How do the earth sciences mediate between the natural and social world? This paper explores the question by focusing on the history of nonfuel mineral resource appraisal from the late nineteenth to the mid twentieth century. It argues that earth sciences early on embraced social scientific knowledge, i.e. economic knowledge, in particular, when it came to determining or deposits and estimating the magnitude of mineral reserves. After 1900, assessing national and global mineral reserves and their "life span" or years of supply became ever more important, scaling up and complementing traditional appraisal practices on the level of individual mines or mining and trading companies. As a consequence, economic methods gained new weight for mineral resource estimation. Natural resource economics as an own field of research grew out of these efforts. By way of example, the mineral resource appraisal assigned to the U.S. Materials Policy Commission by President Harry S. Truman in 1951 is analyzed in more detail. Natural resource economics and environmental economics might be interpreted as a strategy to bring down the vast and holistically conceived object of geological and ecological research, the earth, to human scale, and assimilate it into social matters.

Multa curiosa: Vallisneri's early studies on earth sciences.

In 1687, after he graduated in Medicine, young Antonio Vallisneri (1661-1730) returned in the Duchy of Modena and Reggio. In those years he mainly served as general practitioner; nevertheless, he also devoted many studies to various aspects of the natural sciences. He performed many observations, accurately reporting them in seven Quaderni, which were compiled between 1694 and 1701. Though the Earth sciences occupy only a small part of these diaries, the accuracy of the notes makes them a precious token of the scientific praxis adopted by the author in this field of study. This paper deals with the analysis of these early geological reports, pointing out the main criteria of Vallisneri's experimental method and paying attention to the great significance which these documents had in the elaboration of some of his published works.

Exploring Greenland: science and technology in Cold War settings.

This paper explores a vacant spot in the Cold War history of science: the development of research activities in the physical environmental sciences and in nuclear science and technology in Greenland. In the post-war period, scientific exploration of the polar areas became a strategically important element in American and Soviet defence policy. Particularly geophysical fields like meteorology, geology, seismology, oceanography, and others profited greatly from military interest. While Denmark maintained formal sovereignty over Greenland, research activities were strongly dominated by U.S. military interests. This paper sets out to summarize the limited current state of knowledge about activities in the environmental physical sciences in Greenland and their entanglement with military, geopolitical, and colonial interests of both the USA and Denmark. We describe geophysical research in the Cold War in Greenland as a multidimensional colonial endeavour. In a period of decolonization after World War II, Greenland, being a Danish colony, became additionally colonized by the American military. Concurrently, in a period of emerging scientific internationalism, the U.S. military "colonized" geophysical research in the Arctic, which increasingly became subject to military directions, culture, and rules.