Testing Continental Drift: Constructing the First Palaeomagnetic Path of Polar Wander (1954)

2012 ◽  
Vol 31 (1) ◽  
pp. 111-145 ◽  
Author(s):  
Kenneth Creer ◽  
Edward Irving
Keyword(s):  
Continental Drift ◽  
Subsequent Work ◽  
Global Test ◽  
Field Station ◽  
Physical Test ◽  
Polar Wander ◽  
Cambridge University ◽  
Rock Formations ◽  
Starting Point ◽  
Natural Remanent Magnetisation

We describe the discovery that the natural remanent magnetisation (NRM) of certain rock formations in Britain that are Eocene or older have directions that differed significantly from the Earth's present field and from one another. In 1954 the first author, a third year research student in the Department or Geodesy and Geophysics (DG&G) at Cambridge University, observed that the poles corresponding to these old geomagnetic field directions fell consecutively on a path beginning in the Proterozoic in Arizona, swooped across the Pacific Ocean to the coast of eastern Asia and from there northwards to the present north geographic pole by the middle Tertiary. This was the first path of apparent polar wander (APW) based on the NRM of rocks. This path ought to have been reproducible in all continents had they not moved. Thus was born the first successful physical test of Wegener's Theory of continental drift. The work had its origins several years earlier with the construction in the later 1940s of a very sensitive magnetometer by P. M. S. Blackett at Jodrell Bank, a field station of the University of Manchester. In the summer and autumn of 1951, the second author, a recent geology graduate from Cambridge University, showed that Blackett's instrument, which had been made for an entirely different purpose, was well suited to measuring the NRM of rocks (palaeomagnetism). In the following years Blackett-type magnetometers became the means by which the British path of APW was observed. Although Creer's path was based only on nine poles we show that subsequent work fully justifies its use as a starting point for the successful global test of Wegener's theory that was carried out in the following years. Since then, palaeomagnetic poles and the APW paths derived from them have become the basis for constructing the general frame of reference for palaeogeographic maps, for mapping the past distribution of continents, oceans and orogenic belts, the location of ancient climatic zones and many other applications.

Consideration of a Pharmacological Combinatorial Approach to Inhibit Chronic Inflammation in Alzheimer’s Disease

2019 ◽  
Vol 16 (11) ◽  
pp. 1007-1017 ◽  
Author(s):  
James G. McLarnon
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Animal Models ◽  
Chronic Inflammation ◽  
Preventive Strategy ◽  
Subsequent Work ◽  
Activated Microglia ◽  
Starting Point ◽  
Anti Inflammatory ◽  
Cocktail Approach

A combinatorial cocktail approach is suggested as a rationale intervention to attenuate chronic inflammation and confer neuroprotection in Alzheimer’s disease (AD). The requirement for an assemblage of pharmacological compounds follows from the host of pro-inflammatory pathways and mechanisms present in activated microglia in the disease process. This article suggests a starting point using four compounds which present some differential in anti-inflammatory targets and actions but a commonality in showing a finite permeability through Blood-brain Barrier (BBB). A basis for firstchoice compounds demonstrated neuroprotection in animal models (thalidomide and minocycline), clinical trial data showing some slowing in the progression of pathology in AD brain (ibuprofen) and indirect evidence for putative efficacy in blocking oxidative damage and chemotactic response mediated by activated microglia (dapsone). It is emphasized that a number of candidate compounds, other than ones suggested here, could be considered as components of the cocktail approach and would be expected to be examined in subsequent work. In this case, systematic testing in AD animal models is required to rigorously examine the efficacy of first-choice compounds and replace ones showing weaker effects. This protocol represents a practical approach to optimize the reduction of microglial-mediated chronic inflammation in AD pathology. Subsequent work would incorporate the anti-inflammatory cocktail delivery as an adjunctive treatment with ones independent of inflammation as an overall preventive strategy to slow the progression of AD.

Introduction

2009 ◽  
Author(s):  
David W. Orr
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Political Leader ◽  
Intergovernmental Panel ◽  
Assessment Report ◽  
Cambridge University ◽  
Starting Point ◽  
The Media ◽  
Political Trauma ◽  
E Mail

In our final hour (2003), cambridge university astronomer Martin Rees concluded that the odds of global civilization surviving to the year 2100 are no better than one in two. His assessment of threats to humankind ranging from climate change to a collision of Earth with an asteroid received good reviews in the science press, but not a peep from any political leader and scant notice from the media. Compare that nonresponse to a hypothetical story reporting, say, that the president had had an affair. The blow-dried electronic pundits, along with politicians of all kinds, would have spared no effort to expose and analyze the situation down to parts per million. But Rees’s was only one of many credible and well-documented warnings from scientists going back decades, including the Fourth Assessment Report from the Intergovernmental Panel on Climate Change (2007). All were greeted with varying levels of denial, indifference, and misinterpretation, or were simply ignored altogether. It is said to be a crime to cause panic in a crowded theater by yelling “fire” without cause, but is it less criminal not to warn people when the theater is indeed burning? My starting point is the oddly tepid response by U.S. leaders at virtually all levels to global warming, more accurately described as “global destabilization.” I will be as optimistic as a careful reading of the evidence permits and assume that leaders will rouse themselves to act in time to stabilize and then reduce concentrations of greenhouse gases below the level at which we lose control of the climate altogether by the effects of what scientists call “positive carbon cycle feedbacks.” Even so, with a warming approaching or above 2°C we will not escape severe social, economic, and political trauma. In an e-mail to the author on November 19, 2007, ecologist and founder of the Woods Hole Research Center George Woodwell puts it this way: . . . There is an unfortunate fiction abroad that if we can hold the temperature rise to 2 or 3 degrees C we can accommodate the changes. The proposition is the worst of wishful thinking.

Palaeomagnetic evidence for Proterozoic continental development

1981 ◽  
Vol 301 (1461) ◽  
pp. 265-277 ◽  
Keyword(s):  
North America ◽  
High Latitude ◽  
Baltic Shield ◽  
Continental Drift ◽  
Polar Wander ◽  
Late Proterozoic ◽  
Apparent Polar Wander Path ◽  
Orogenic Uplift ◽  
The Baltic ◽  
Opening And Closing

The palaeomagnetic record of continental drift during the Proterozoic is reasonably complete for North America (including Greenland and the Baltic Shield), less complete for Africa and Australia, and fragmentary elsewhere. Palaeomagnetic poles of similar age from different cratons or structural provinces of any one continent tend to fall on a common apparent polar wander path (a.p.w.p.), indicating no major (> 1000 km) intercratonic movements. On this evidence, Proterozoic orogens and mobile belts are essentially ensialic in origin. However, the palaeomagnetic record has systematic gaps. In highly metamorphosed orogens (amphibolite grade and above), remagnetization dating from post-orogenic uplift and cooling is pervasive. Collisional and ensialic orogenesis cannot then be distinguished. Palaeopoles from different continents do not follow a common a.p.w.p. They record large relative rotations and palaeolatitude shifts. A recurrent pattern appears in the late Proterozoic drift of North America. At approximately 200 Ma intervals (at about 1250, 1050, 850 and 600 Ma B.P .), the continent returned to the same orientation and (equatorial) latitudes from various rotations and high-latitude excursions. Lacking detailed a.p.w.ps. from other continents, it is not possible to say if these motions represent Wilson cycles of ocean opening and closing in the Phanerozoic style, but they do require minimum drift rates of 50—60 mm/a, comparable to the most rapid present-day plate velocities.

scholarly journals Measuring Fairness, Inequality, and Big Data: Social Choice Since Arrow

2019 ◽  
Vol 22 (1) ◽  
pp. 435-460
Author(s):  
John W. Patty ◽  
Elizabeth Maggie Penn
Keyword(s):  
Big Data ◽  
Social Choice ◽  
Institutional Design ◽  
Choice Theory ◽  
Social Choice Theory ◽  
Impossibility Theorem ◽  
Axiomatic Method ◽  
Subsequent Work ◽  
Fundamental Interest ◽  
Starting Point

Kenneth J. Arrow was one of the most important intellectuals of the twentieth century, and his “impossibility theorem” is arguably the starting point of modern, axiomatic social choice theory. In this review, we begin with a brief discussion of Arrow's theorem and subsequent work that extended the result. We then discuss its implications for voting and constitutional systems, including a number of seminal results—both positive and negative—that characterize what such systems can accomplish and why. We then depart from this narrow interpretation of the result to consider more varied institutional design questions such as apportionment and geographical districting. Following this, we address the theorem's implications for measurement of concepts of fundamental interest to political science such as justice and inequality. Finally, we address current work applying social choice concepts and the axiomatic method to data analysis more generally.

Unification of the Australian cratons before the formation of Nuna

2020 ◽  
Author(s):  
Uwe Kirscher ◽  
Ross Mitchell ◽  
Yebo Liu ◽  
Adam Nordsvan ◽  
Grant Cox ◽  
...  
Keyword(s):  
Building Blocks ◽  
Plate Motion ◽  
Central Pacific ◽  
Polar Wander ◽  
Central Pacific Ocean ◽  
The North ◽  
Rock Formations ◽  
Pine Creek ◽  
The Individual ◽  
Related Characteristic

<p>The paleogeography and chronology of the Paleoproterozoic supercontinent Nuna are highly debated. To further test the paleogeography of Australian cratons in the leadup to Nuna formation, we present new paleomagnetic results from two Paleoproterozoic rock formations in North Australia. First, we obtained paleomagnetic directions from the 1825±4 Ma, bimodal Plum Tree Creek Volcanics sequence located within the Pine Creek Inlier of the North Australian Craton. Second, we studied the 1855±2 Ma layered mafic-ultramafic ‘Toby’ intrusion from the Kimberley Craton (KC). Samples from both study areas reveal high quality, stable, magnetite related characteristic remanent magnetization directions. Combining within-site clustered mean directions, we obtained two paleopoles, which plot proximal to each other in the present day central Pacific Ocean, off the east coast of Australia. These results agree with previous interpretation that the Kimberly Craton was amalgamated with the rest of the North Australian Craton (NAC) prior to ca. 1.85 Ga. Comparing these new results with slightly younger poles from the NAC and slightly older, rotated poles form the West Australian Craton (WAC) reveal a high degree of clustering suggesting very minimal absolute plate motion between ca. 1.9-1.85 and 1.6 Ga before the final amalgamation of Nuna. All available paleomagnetic poles agree with an assembly, or close juxtaposition, of the two major Australian cratons (NAC and WAC) before 1.8 Ga. Furthermore, the individual virtual geomagnetic poles from the potentially slow cooled Toby intrusion show a non-fisherian distribution along a great circle. This spread might be related to previously interpreted major true polar wander events based on Laurentian data, which would be global if such an interpretation is correct. The assembly of proto-Australia prior to ca. 1.85 Ga roughly 250 to 300 Myr before the final stage of supercontinent Nuna’s amalgamation ca. 1.6 Ga suggests that assembling of major building blocks, such as Australia and Laurentia for the supercontinent Nuna and Gondwana for the supercontinent Pangea, is an important step in the formation of supercontinents.</p>

Tell me what's underneath! Using a model to investigate core sampling methodology with secondary school students

2020 ◽  
Author(s):  
Alessandra Borghini
Keyword(s):  
Secondary School ◽  
Learning Outcomes ◽  
Teaching Sequence ◽  
Learning Sequence ◽  
School Students ◽  
The Past ◽  
Core Sampling ◽  
Rock Formations ◽  
Starting Point ◽  
Using Data

<p>What is under our feet? How can we study something that we cannot directly see? How can we reconstruct Earth’s history?<br>To find answers to these interesting questions scientists developed different methodologies to investigate soil, rock formations, as well as the deeper structure of Earth’s interior. The same questions can be used as a starting point for many teaching activities.<br>In the teaching activity we experimented with 11-12 years old students in a Secondary School in Italy, we used a model made with inexpensive materials to discover core sampling, one of the methodologies used by geologists to investigate the outermost part of our planet and gather important information to reconstruct Earth’s history. <br>One of the aims of the teaching sequence is to make students understand the work of geologists and how they can discover what happened in the past by studying rocks. These activities are also a way to help students to develop important skills such as formulating hypotheses, carrying on investigations and using data to validate a hypothesis.<br>In this poster I present the activities and discuss some observations on students' drawings and descriptions, collected during the learning sequence to better understand students’ learning process and the learning outcomes. </p><p> </p>

scholarly journals The Art of Everyday Haunting

Derrida Today ◽  
2012 ◽  
Vol 5 (2) ◽  
pp. 199-213
Author(s):  
David Coughlan
Keyword(s):  
The Body ◽  
The Other ◽  
Subsequent Work ◽  
Starting Point ◽  
The Dead ◽  
Work Of Mourning ◽  
First Words

The question of where ghosts live can hardly be addressed without speaking of a haunted house. This essay reads Don DeLillo's novel The Body Artist, in which there is a ghost called Mr. Tuttle who haunts the house of Lauren Hartke, the body artist, as a text grafted onto Jacques Derrida's Dissemination. The essay takes as its starting point the first words spoken in DeLillo's text, ‘I want to say something but what’, a quasi-question directed to Lauren by her husband Rey, in order to ask if it can ever be said what lies on the other side of ‘what’, or if it remains forever unknowable, or unheard, at an ‘infinite remove’, even if it is one's self. It is Rey's suicide, and Lauren's subsequent work of mourning, which locates DeLillo's phrase within the context of Derrida's efforts, again and again, to give words to those whose voices are absent: the lost friend, the other self, the dead. To Lauren's question, ‘What am I supposed to say?’ Derrida replies, ‘Speaking is impossible, but so too would be silence or absence’. Through the ghostly form of Mr. Tuttle, DeLillo's work tells of the various mimetisms by which the silent speaker is heard and remembered.

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