Multidecadally resolved polarity oscillations during a geomagnetic excursion

Polarity reversals of the geomagnetic field have occurred through billions of years of Earth history and were first revealed in the early 20th century. Almost a century later, details of transitional field behavior during geomagnetic reversals and excursions remain poorly known. Here, we present a multidecadally resolved geomagnetic excursion record from a radioisotopically dated Chinese stalagmite at 107–91 thousand years before present with age precision of several decades. The duration of geomagnetic directional oscillations ranged from several centuries at 106–103 thousand years before present to millennia at 98–92 thousand years before present, with one abrupt reversal transition occurring in one to two centuries when the field was weakest. These features indicate prolonged geodynamo instability. Repeated asymmetrical interhemispheric polarity drifts associated with weak dipole fields likely originated in Earth’s deep interior. If such rapid polarity changes occurred in future, they could severely affect satellites and human society.

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Magnetic World: The Historiography of an Inherently Complex Science, Geomagnetism, in The 20th Century

Earth Sciences History ◽

10.17704/eshi.26.2.12072212x1n53521 ◽

2007 ◽

Vol 26 (2) ◽

pp. 281-299 ◽

Cited By ~ 1

Author(s):

Gregory Good

Keyword(s):

Magnetic Field ◽

20Th Century ◽

Geomagnetic Field ◽

Plate Tectonics ◽

Radiation Belts ◽

Problem Area ◽

Early 20Th Century ◽

The Earth ◽

History Of ◽

Field Lines

The 20th century witnessed a succession of remarkable developments in the history of geomagnetic research. After 1900, geomagnetic researchers increased their activity as they adopted theories by C. F. Gauss and J. C. Maxwell and developed means to bridge the gulf between these theories and masses of data of global phenomena. This paper outlines three main streams in 20th-century geomagnetic research: investigations of processes deep inside the Earth that produce the main geomagnetic field, examinations of crustal magnetism, and research into processes on the edge of space, where Earth's magnetic field interacts with the interplanetary environment. This discussion places these research streams in the historiographic context of disciplinary specialization and transformation. In the early 20th century, geomagnetic researchers thought of their domain as all of Earth's magnetic and electric phenomena. In mid-century, however, many researchers began to narrow their gaze to one problem area or another. This specialization contributed to a period of dramatic developments in the latter half of the century: geodynamo theory, paleomagnetic evidence of plate tectonics, computer modeling of magnetic reversals, and discovery of the solar wind, radiation belts, and magnetic substorms. But there was more to this period than simple specialization. As researchers gradually shifted their research programs, their methods, instruments, and theories moved from one program to another, researchers sometimes going with them. Chameleons and opportunists frequently left one research program for another, more promising one. This paper closes with a discussion of the possibility of "re-connection" among these specializations, as researchers have begun once again to communicate across inter-field lines.

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The puzzle of plague transmission

Microbiology Australia ◽

10.1071/ma20047 ◽

2020 ◽

Vol 41 (4) ◽

pp. 172

Author(s):

Patricia Morison ◽

Ian Morison

Keyword(s):

20Th Century ◽

Early 20Th Century ◽

Human Society ◽

Human History ◽

Way Of Life ◽

Bubonic Plague ◽

Protective Measures ◽

Death Toll ◽

Microbiological Research ◽

The Way

Bubonic plague is among the most feared diseases in human history, not only because of its death toll but also for its consequential impact on the way of life and economic endeavour of human society. Every few hundred years the advance of a pandemic has raised impotent fear, until the early 20th century when microbiological research solved the mystery of how it is transmitted to its victims, opening the way to protective measures.

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The Global Groundwater Revolution

Oxford Research Encyclopedia of Environmental Science ◽

10.1093/acrefore/9780199389414.013.632 ◽

2019 ◽

Cited By ~ 1

Author(s):

Jac van der Gun

Keyword(s):

20Th Century ◽

Human Behavior ◽

Historical Change ◽

Early 20Th Century ◽

Human Society ◽

Rapid Intensification ◽

Local Conditions ◽

Groundwater Systems ◽

Ancient Times ◽

Main Components

Human behavior in relation to groundwater has remained relatively unchanged from ancient times until the early 20th century. Intercepting water from springs or exploiting shallow aquifers by means of wells or qanats was common practice worldwide, but only modest quantities of groundwater were abstracted. In general, the resource was taken for granted in absence of any knowledge regarding groundwater systems and their vulnerability. During the 20th century, however, an unprecedent change started spreading globally—a change so drastic that it could be called the Global Groundwater Revolution. It did not surface simultaneously everywhere but rather encroached into different regions as waves of change, with varied timing, depending on local conditions. This Global Groundwater Revolution has three main components: (1) rapid intensification of the exploitation of groundwater, (2) fundamentally changing views on groundwater, and (3) the emergence of integrated groundwater management and governance. These three components are mostly interdependent, although their emergence and development tend to be somewhat asynchronous. The Global Groundwater Revolution marks a radical historical change in the relation between human society and groundwater. It has taken benefits produced by groundwater to an unprecedented level, but their sustainability is assured only if there is good groundwater governance.

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