Celebrating Marie Tharp

doi:10.1126/science.abe7084

GSTDTAP > 气候变化

DOI	10.1126/science.abe7084
	Celebrating Marie Tharp
	Marco Romano; Francesco Latino Chiocci
	2020-12-18
发表期刊	Science
出版年	2020
英文摘要	The 30th of July 2020 marked the centenary of the birth of a woman who was central to the development of the field of Earth sciences: Marie Tharp, a pioneer of ocean floor cartography and marine geology. Her work was crucial in reintroducing a mobilist (drift) vision of Earth and for the development of the plate tectonics revolution in the early 1960s. The theory of continental drift proposed by Alfred Wegener in 1912—which was based on sound correspondences between rocks, fossils, and geological structures on opposite sides of the Atlantic—was initially heavily criticized and rejected by the scientific community. Some paleontologists invoked the past presence of continental bridges that subsequently collapsed to explain the similarity of the faunas between the two sides of the ocean. The hardest attack came from the field of geophysics, which perceived the biggest obstacles to be the identification of a possible “driving force” or “engine” that could move rigid crust, causing such prodigious continental drift. However, Wegener, by combining geological data that included isostasy and the evidence of radiogenic heat, proposed two main possible mechanisms for the drifting of fragments of continental crust (the so called sial)—that is, “Pohlflucht” (gravitational migration away from the poles) and/or solid tides induced by the Moon—but neither was considered plausible or able to generate such movements. A crucial missing piece in this debate was in-depth knowledge of the ocean floor, which covers more than 70% of Earth's surface. Indeed, until the first half of the past century, almost nothing was known about the real composition and physiography of the ocean floor, an area of the planet too large to be ignored in geological models at the macroscale. This is where, as some had begun to suspect, the evidence for the driving force of continental drift was hiding. Here, Marie Tharp played a key role in the 1950s when, by comparing bathymetric profiles across the Atlantic Ocean, she realized the continuity of the ocean ridges and the presence of an axial valley testifying to their expansion. The mid-Atlantic ridge was discovered by Tharp in 1952 by comparing six sheets of cruise profiles, but the existence of a V-shaped rift was initially cautiously rejected by her colleague Bruce Heezen because its mobilist implications were too radical for a scientific community that had largely rejected, if not ridiculed, the Wegener continental drift hypotheses. In a later interview, Heezen declared, “I discounted it as girl talk and didn't believe it for a year.” Subsequent research by Tharp and Heezen at the Lamont Geological Observatory of Columbia University (now the Lamont-Doherty Earth Observatory) led to a completely new and unexpected picture of the ocean floor, providing a crucial piece of data (together with magnetic reversal and hypocenter location) that would lead in a few years to the plate tectonic hypothesis. Heezen made several important discoveries in marine geology, especially with regard to sea-floor sediments and currents, challenging the traditional “permanentist” geological conception; he was also one of the principal collectors of data from the sea floor, with a 30-year project of collaborations that resulted in the first world map of the ocean floor in 1977, a document distinctive for its geological importance. By then, Heezen had devoted his professional life to studying the secrets of the oceans, dying at sea from a heart attack aboard a submarine in 1977. Having graduated with degrees in both geology and mathematics, Marie Tharp had skills that proved to be fundamental to the realization of ocean-basin topographic maps, a process that required in-depth knowledge of geography, mathematics, and geology. By using her mathematic skills, she was able to transform the huge amount of collected raw bathymetric data (the echo-sounders were in their early stage, having been invented only a few decades before) into profiles and maps. From the early 1960s onward, Heezen and Tharp published influential papers with profiles, graphs, and contour diagrams focused on the mid-Atlantic ridge and all the systems of fractures affecting this major feature. The ability to graphically transform ocean floor data into visible objects considerably facilitated new inferences and hypotheses, as well as easier communication of the evidence on which new theories could be soundly based. It was precisely these graphical results that inspired authors like J. Tuzo Wilson to propose an entirely new category of “faults”: the transform faults, a system of faults along a plate boundary characterized by a predominantly horizontal motion. Once they were appreciated, transform faults played a fundamental role in the paradigm shift of plate tectonics in geology. The publication in 1977 by Heezen and Tharp of the legendary first complete world map of the ocean floors (see the photo ) revealed to the general public the thousands-of-kilometers-long complex system of ocean ridges, fracture zones, seamounts, and trenches, revealing the geodynamic processes shaping our planet. It is regrettable to note that at the beginning of her career, Marie Tharp, as a woman, was not allowed to board the ships that were collecting the data she was studying and that her first hypotheses on sea-floor spreading were treated as mere “girl talk.” Now, her intuitions have been fully appreciated and vindicated, stressing the too-often-ignored central contribution of women to the development of science.
领域	气候变化 ; 资源环境
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引用统计
文献类型	期刊论文
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/308352
专题	气候变化资源环境科学
推荐引用方式 GB/T 7714	Marco Romano,Francesco Latino Chiocci. Celebrating Marie Tharp[J]. Science,2020.
APA	Marco Romano,&Francesco Latino Chiocci.(2020).Celebrating Marie Tharp.Science.
MLA	Marco Romano,et al."Celebrating Marie Tharp".Science (2020).