MAGNETIC ANOMALY EFFECTS DUE TO APPROXIMATING INFINITE RECTANGULAR PRISM SOURCES BY INFINITE LINE OR INFINITE SHEET SOURCES

Geophysics ◽  
1975 ◽  
Vol 40 (3) ◽  
pp. 530-537 ◽  
Author(s):  
J. N. Shapiro ◽  
G. Weynand ◽  
A. F. Gangi
Keyword(s):  
Magnetic Anomaly ◽  
Plate Tectonics ◽  
Rectangular Prism ◽  
Magnetization Distribution ◽  
The World ◽  
Simplifying Assumptions ◽  
Crustal Magnetization ◽  
Infinite Line ◽  
Ridge System

The inversion of oceanic magnetic anomaly data to obtain the crustal magnetization requires some assumptions regarding the magnetization distribution (Parker and Huestis, 1974). Two simplifying assumptions typically made for data near ridge systems are that the source magnetization is lineated parallel to the ridge system and that it is unidirectional. These assumptions follow directly from the theory of plate tectonics and have been used near the major ridge systems of the world. The presence of transform faulting can offset the lineations usually observed and render the first assumption invalid. In this note, only those cases in which both assumptions are valid will be considered.

Geophysical, evolutionary and ecological processes interact to drive phylogenetic dispersion in angiosperm assemblages along the longest elevational gradient in the world

2019 ◽  
Vol 190 (4) ◽  
pp. 333-344 ◽  
Author(s):  
Hong Qian ◽  
Brody Sandel ◽  
Tao Deng ◽  
Ole R Vetaas
Keyword(s):  
Plate Tectonics ◽  
Biotic Interactions ◽  
Elevational Gradient ◽  
Flowering Plants ◽  
Ecological Processes ◽  
Phylogenetic Structure ◽  
Phylogenetic Relatedness ◽  
The World ◽  
Net Relatedness Index ◽  
Phylogenetic Dispersion

AbstractEcologists have embraced phylogenetic measures of assemblage structure, in large part for the promise of better mechanistic inferences. However, phylogenetic structure is driven by a wide array of factors from local biotic interactions to biogeographical history, complicating the mechanistic interpretation of a pattern. This may be particularly problematic along elevational gradients, where rapidly changing physical and biological conditions overlap with geological and biogeographical history, potentially producing complex patterns of phylogenetic dispersion (relatedness). We focus on the longest elevational gradient of vegetation in the world (i.e. c. 6000 m in Nepal) to explore patterns of phylogenetic dispersion for angiosperms (flowering plants) along this elevational gradient. We used the net relatedness index to quantify phylogenetic dispersion for each elevational band of 100 m. We found a zig-zag pattern of phylogenetic dispersion along this elevational gradient. With increasing elevation, the phylogenetic relatedness of species decreased for the elevational segment between 0 and c. 2100 m, increased for the elevational segment between 2100 and c. 4200 m, and decreased for the elevational segment above c. 4200 m. We consider this pattern to be a result of the interaction of geophysical (e.g. plate tectonics) and eco-evolutionary processes (e.g. niche conservatism and trait convergence). We speculate on the mechanisms that might have generated this zig-zag pattern of phylogenetic dispersion.

Drummond Hoyle Matthews. 5 February 1931 — 20 July 1997

1999 ◽  
Vol 45 ◽  
pp. 275-294
Author(s):  
Robert S. White
Keyword(s):  
Graduate Student ◽  
Plate Tectonics ◽  
Seafloor Spreading ◽  
Marine Geophysics ◽  
Scientific Legacy ◽  
The World ◽  
Work Done

Drummond (Drum) Matthews was a leader who gave himself selflessly for the good of his students and science. He is best known for his work with Fred Vine (F.R.S. 1974), then his graduate student, on the seafloor spreading hypothesis, which underpinned the plate tectonics revolution, and for the work done under his leadership by the Cambridge marine geophysics group and the British Institutions' Reflection Profiling Syndicate (BIRPS). But perhaps his most enduring scientific legacy lies in his many former students, now in positions of leadership and responsibility around the world, who continue to make significant contributions to the health of science.

NEW TARGETS FOR THE STUDIES OF BIOMECHANICAL, ENDOCRINOLOGIC, GENETIC AND PHARMACEUTICAL EFFECTS ON BONES: BONE'S "NEPHRON EQUIVALENTS", MUSCLE, NEUROMUSCULAR PHYSIOLOGY

2000 ◽  
Vol 04 (02) ◽  
pp. 67-84 ◽  
Author(s):  
Harold M. Frost
Keyword(s):  
Common Sense ◽  
Plate Tectonics ◽  
Interdisciplinary Communication ◽  
Renal Physiology ◽  
Kidney Cells ◽  
Renal Cells ◽  
Effector Cells ◽  
The World ◽  
Utah Paradigm ◽  
Bone Physiology

As age, experience and common sense look at biomechanical, hormonal, genetic and other roles in bone physiology and its disorders, two questions can arise: (a) How did we fail? (b) How could we make it better? The acerbic Sam Johnson said that to teach new things, we should use examples of already known ones. If so, an analogy might help to clarify this article's message for people who work with bones and their disorders. Assume this: (a) Mythical physiologists were taught that renal physiology depends on "kidney cells" but were taught nothing about nephrons; (b) so they explained renal health and disorders in those terms. (c) For many decades, they "knew" that view was correct (as the ancients "knew" the world was flat). (d) But then others described nephrons and some errors their properties revealed in those views about renal physiology; (e) so controversies began. Today, an analogous situation confronts real biomechanicians and physiologists. (i) Most of them were taught that osteoblasts and osteoclasts (bone's "effector cells") explain bone physiology without "nephron-equivalent" input, so they explained bone disorders and mechanical effects in those terms. (ii) Yet nephron-equivalent mechanisms and functions, including biomechanical ones, in bones have the same operational relationship to their cells, health and disorders as nephrons and their functions do to renal cells, health and disorders. (iii) Adding that knowledge to former views led to the Utah paradigm of skeletal physiology. It also revealed errors in many former views about bone physiology; (iv) so real controversies have begun. Biomechanicians, physiologists, clinicians and pharmacologists from whom poor interdisciplinary communication hid that paradigm could think the view in (i) above remains valid, and keep analyzing data and designing studies within its constraints. Like Wegner's idea of plate tectonics in geology, the Utah paradigm came before its field was ready, so others fought it. But while the plate-tectonics war was won, it has just begun for the Utah paradigm. This article reviews how such things could apply to bone and some of their implications. Its conclusion offers succinct answers to the italicized questions above.

Magnetic exploration of ocean crust for craters of impact origin: Model results

Geophysics ◽  
1991 ◽  
Vol 56 (8) ◽  
pp. 1153-1157 ◽  
Author(s):  
Andrew R. Ochadlick
Keyword(s):  
Magnetic Anomaly ◽  
Deep Ocean ◽  
Point Of View ◽  
Ocean Floor ◽  
Magnetic Data ◽  
Data Sets ◽  
Ocean Crust ◽  
Crustal Magnetization ◽  
Simple Potential ◽  
The Impact

Magnetic data sets over deep ocean areas may contain clues to the existence of craters formed by the impact of an extraterrestrial body with the Earth’s ocean crust. To aid in the magnetic exploration of the ocean crust for oceanic impact craters, basic but effective computations from an impact model are studied from an aeromagnetic point of view. The main assumption of the analysis is that a sufficiently large impact can excavate large volumes of magnetized basalt, vaporize basalt, and raise basalt to temperatures above the Curie temperature (approximately 500°C) to alter the preimpact magnetization of the ocean floor and result in a magnetic anomaly being associated with an oceanic impact crater. In the absence of an existing theory on the influence of impacts on ocean crustal magnetization, the representation of a crater on the ocean floor by a simple potential provides, apparently for the first time, quantitative estimates of the crater’s magnetic anomaly along a horizontal surface. Numerical results from the model suggest that the detection of the anomaly of a Cretaceous‐Tertiary (K-T) type of impact is well within the capabilities of aeromagnetic technology.

scholarly journals National Geophysical Data Center candidate for the World Digital Magnetic Anomaly Map

2007 ◽  
Vol 8 (6) ◽  
pp. n/a-n/a ◽  
Author(s):  
S. Maus ◽  
T. Sazonova ◽  
K. Hemant ◽  
J. D. Fairhead ◽  
Dhananjay Ravat
Keyword(s):  
Magnetic Anomaly ◽  
Data Center ◽  
Geophysical Data ◽  
The World ◽  
National Geophysical Data ◽  
Anomaly Map ◽  
National Geophysical Data Center

scholarly journals This Is How the World Moves

Eos ◽  
2019 ◽  
Vol 100 ◽  
Author(s):  
Heather Goss
Keyword(s):  
Plate Tectonics ◽  
The World

In October, we celebrate AGU’s Centennial by looking under our feet, where the relatively new study of plate tectonics is evolving rapidly.

scholarly journals Neotectonic mountain uplift and geomorphology

2019 ◽  
pp. 3-26
Author(s):  
C. D. Ollier ◽  
C. F. Pain
Keyword(s):  
Plate Tectonics ◽  
Volcanic Rocks ◽  
Passive Margin ◽  
Continental Margins ◽  
Lateral Compression ◽  
Mountain Building ◽  
Topographic Features ◽  
Active Margins ◽  
The World ◽  
Fold Belts

Mountains are topographic features caused by erosion after vertical uplift or mountain building. Mountain building is often confused with orogeny, which today means the formation of structures in fold belts. The common assumption that folding and mountain building go together is generally untrue. Many mountains occur in unfolded rocks, granites and volcanic rocks, so there is no direct association of folding and mountain building. In those places where mountains are underlain by folded rocks the folding pre-dates planation and uplift. The age of mountains is therefore not the age of the last folding (if any) but the age of vertical uplift. Since mountains are not restricted to folded rocks, lateral compression is not required to explain the uplift. A compilation of times of uplift of mountains around the world shows that a major phase of tectonic uplift started about 6 Ma, and much uplift occurred in the last 2 Ma. This period is known as the Neotectonic Period. It is a global phenomenon including mountains on passive continental margins, and those in deep continental interiors. Several hypotheses of mountain building have problems with this timing. Some fail by being only able to make mountains out of folded rock at continental margins. Many translate the vertical uplift into lateral compression, but vertical uplift alone can create mountains. The Neotectonic Period has important implications for geomorphology, climate and global tectonics. In geomorphology it does not fit into conventional theories of geomorphology such as Davisian or King cycles of erosion. Neotectonic uplift might initiate several cycles of erosion, but most planation surfaces are much older than the Neotectonic Period. The increasing relief associated with Neotectonic uplift affected rates of erosion and sedimentation, and also late Cenozoic climate. The Neotectonic Period does not fit within plate tectonics theory, in which mountains are explained as a result of compression at active margins: mountains in other locations are said to have been caused by the same process but further back in time. This is disproved by the young age of uplift of mountains in intercontinental and passive margin positions. Subduction is supposed to have been continuous for hundreds of millions of years, so fails to explain the world-wide uplifts in just a few million years. Geomorphologists should be guided by their own findings, and refrain from theory-driven hypotheses of plate collision or landscape evolution.

scholarly journals Interpolation of magnetic anomalies over an oceanic ridge region using an equivalent source technique and crust age model constraint

2021 ◽  
Author(s):  
Duan Li ◽  
Jinsong Du ◽  
Chao Chen ◽  
Qing Liang ◽  
Shida Sun
Keyword(s):  
Plate Tectonics ◽  
Magnetic Anomalies ◽  
Background Field ◽  
Source Model ◽  
Magnetic Data ◽  
Magnetization Distribution ◽  
Equivalent Source ◽  
Oceanic Ridge ◽  
Age Model ◽  
Equivalent Sources

Abstract. Marine magnetic surveys over oceanic ridge regions are of great interest for investigations of structure and evolution of oceanic crust, and have played a key role in developing the theory of plate tectonics (Dyment, 1993; Maus et al, 2007; Vine and Matthews, 1963). In this study, we propose an interpolation approach based on the dual-layer equivalent source model for the generation of a magnetic anomaly map based on sparse survey line data over oceanic ridge areas. In this approach, information from an ocean crust age model is utilized as constraint for the inversion procedure. The constraints can affect the magnetization distribution of equivalent sources following crust age. The results of synthetic tests show that the obtained magnetic anomalies have higher accuracy than those obtained by other interpolation methods. Meanwhile, considering the unclear on the true magnetization directions of sources and the background field in the synthetic model, well interpolation result can still be obtained. We applied the approach to magnetic data obtained from five survey lines east of the Southeast Indian Ridge. This prediction result is useful to improve the lithospheric magnetic field models WDMAMv2 and EMAG2v3, in the terms of spatial resolution and the consistency with observed data.

Plate Tectonics

2021 ◽  
pp. 82-113
Author(s):  
Elisabeth Ervin-Blankenheim
Keyword(s):  
World War Ii ◽  
Plate Tectonics ◽  
Continental Drift ◽  
Ocean Floor ◽  
Mountain Range ◽  
World War ◽  
Tectonic Plates ◽  
The World ◽  
Geologic Time Scale ◽  
Viable Mechanism

This chapter illustrates the most significant revolution in the understanding of the Earth discovered in the last 75 years, plate tectonics. The theory of plate tectonics is the second overarching precept of the field of geology (after the geologic time scale). Plate tectonics and its history as a theory are traced in this chapter. Early explorers and others had noticed the apparent fit in the shapes of the continents, but these ideas were not explicitly stated until Alfred Wegener detailed his evidence for the drift of the continents, though he had no viable mechanism on how the drift would have occurred. World War II technology, including sonar and radar, allowed scientists to understand the ocean floor. Rather than a flat, featureless plain, they found a vast undersea mountain range known as the mid-oceanic ridge that wraps around the world like seams on a baseball. Harry Hess proposed a new mechanism for continental drift through mantle convection cells, causing seafloor spreading. These ideas were confirmed by magnetic surveys and subsequent research, leading to the theory of plate tectonics. A final section looks at the maturation of the theory as geologists continue to learn more details about the movement and intricacies of the tectonic plates.

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