Transforms are forever

2021 ◽  
Author(s):  
Paola Vannucchi ◽  
David Iacopini ◽  
Jason P. Morgan
Keyword(s):  
Fluid Flow ◽  
Seismic Activity ◽  
Plate Tectonics ◽  
Driving Forces ◽  
Permanent Deformation ◽  
Oceanic Lithosphere ◽  
Ocean Floor ◽  
Spreading Center ◽  
Transform Faults ◽  
Recent Earthquakes

<p>According to Plate Tectonics, fracture zones (FZs) are born at Transform Faults (TFs), which leave behind "inactive" FZs traces as scars on the seafloor that reflect their initial use as one side of a strike-slip transform fault. FZs were originally thought to "heal" as the oceanic lithosphere cooled and strengthened with time. However, the occurrence of recent earthquakes reveals that FZs can be associated with significant seismic activity (for example during the recent Mw 8.6 2012 EQ offshore Sumatra and Mw 7.9 2018 EQ offshore SE Kodiak), and also with permanent deformation that occurs well after passage through the TF.</p><p>The TF at the spreading center is known to be accompanied by the formation of the transform valley which exposes serpentinized peridotite to the ocean floor. Valley relief itself can drive fluid flow that promotes continued serpentinization, and also cooling- and volume-change-linked stress variations. Off-axis seismicity suggests that FZs remain weaker that neighbouring oceanic lithosphere. The transform valley relief in general persists as a fracture zone valley that itself can continue to be a major drive of fluid flow even in the “healed” oceanic lithosphere. After reviewing evidence for FZ activity on (normal) ocean floor we will focus on the long-lived impact of FZs at continental margins. Offshore/onshore evidence of ongoing deformation at FZs is observed through seismic activity at both the western Brazilian and eastern Ghana-Côte d’Ivoire ends of the Romanche FZ. The western Brazil end is also characterized by recent folding and faulting, both offshore across the FZ, and onshore co-linearly with FZ extensions into the continent. Seismic activity in continental Brazil is focused where the FZ intersects the continental margin. This activity suggests that FZs remain as permanent weak lithospheric heterogeneities that are able to store elastic strain.</p><p>The reasons why FZs remain active are still poorly understood. Possible causes include i) effects of serpentinization that occurs both in the TF and in the FZ through hydrothermal fluid/mantle interaction, ii) thermal stress, iii) changing tectonic stresses related to plate driving forces.</p>

All at Sea

2018 ◽  
Author(s):  
Roy Livermore
Keyword(s):  
Plate Tectonics ◽  
First Generation ◽  
Basaltic Magma ◽  
Ocean Floor ◽  
Tennis Ball ◽  
Magma Chambers ◽  
Transform Faults ◽  
Ocean Ridges ◽  
Sea Floor Spreading ◽  
Ocean Ridge

According to first-generation plate tectonics, sea-floor spreading was nice and simple. Plates were pulled apart at mid-ocean ridges, and weak mantle rocks rose to fill the gap and began to melt. The resulting basaltic magma ascended into the crust, where it ponded to form linear ‘infinite onion’ magma chambers beneath the mid-ocean tennis-ball seam. At frequent intervals, vertical sheets of magma rose from these chambers to the surface, where they erupted to form new ocean floor or solidified to form dykes, in the process acquiring a magnetization corresponding to the geomagnetic field at the time. Mid-ocean ridge axes were defined by rifted valleys and divided into segments by transform faults with offsets of tens to hundreds of kilometres, resulting in the staircase pattern seen on maps of the ocean floor. All mid-ocean ridges were thus essentially identical. Such a neat and elegant theory was bound to be undermined as new data were acquired in the oceans.

The Paving Stone Theory of World Tectonics

2018 ◽  
Author(s):  
Roy Livermore
Keyword(s):  
Indian Ocean ◽  
Plate Tectonics ◽  
Earth Science ◽  
Transform Faults ◽  
Plate Motions ◽  
Euler’S Theorem ◽  
History Of ◽  
New Ideas ◽  
Entire History ◽  
The Indian Ocean

Tuzo Wilson introduces the concept of transform faults, which has the effect of transforming Earth Science forever. Resistance to the new ideas is finally overcome in the late 1960s, as the theory of moving plates is established. Two scientists play a major role in quantifying the embryonic theory that is eventually dubbed ‘plate tectonics’. Dan McKenzie applies Euler’s theorem, used previously by Teddy Bullard to reconstruct the continents around the Atlantic, to the problem of plate rotations on a sphere and uses it to unravel the entire history of the Indian Ocean. Jason Morgan also wraps plate tectonics around a sphere. Tuzo Wilson introduces the idea of a fixed hotspot beneath Hawaii, an idea taken up by Jason Morgan to create an absolute reference frame for plate motions.

Advanced Geodynamics

2021 ◽  
Author(s):  
David T. Sandwell
Keyword(s):  
Plate Tectonics ◽  
Driving Forces ◽  
Data Sets ◽  
Earthquake Cycle ◽  
Mathematical Methods ◽  
Graduate Course ◽  
Field Development ◽  
Linear Partial Differential Equations ◽  
Global Data Sets ◽  
Global Data

David Sandwell developed this advanced textbook over a period of nearly 30 years for his graduate course at Scripps Institution of Oceanography. The book augments the classic textbook Geodynamics by Don Turcotte and Jerry Schubert, presenting more complex and foundational mathematical methods and approaches to geodynamics. The main new tool developed in the book is the multi-dimensional Fourier transform for solving linear partial differential equations. The book comprises nineteen chapters, including: the latest global data sets; quantitative plate tectonics; plate driving forces associated with lithospheric heat transfer and subduction; the physics of the earthquake cycle; postglacial rebound; and six chapters on gravity field development and interpretation. Each chapter has a set of student exercises that make use of the higher-level mathematical and numerical methods developed in the book. Solutions to the exercises are available online for course instructors, on request.

scholarly journals Intraplate volcanism triggered by bursts in slab flux

2020 ◽  
Vol 6 (51) ◽  
pp. eabd0953
Author(s):  
Ben R. Mather ◽  
R. Dietmar Müller ◽  
Maria Seton ◽  
Saskia Ruttor ◽  
Oliver Nebel ◽  
...  
Keyword(s):  
Transition Zone ◽  
Plate Tectonics ◽  
Isotope Geochemistry ◽  
Plate Boundary ◽  
Oceanic Lithosphere ◽  
Mantle Transition Zone ◽  
Age Progression ◽  
Intraplate Volcanism ◽  
Enriched Mantle ◽  
Eastern Australia

Long-lived, widespread intraplate volcanism without age progression is one of the most controversial features of plate tectonics. Previously proposed edge-driven convection, asthenospheric shear, and lithospheric detachment fail to explain the ~5000-km-wide intraplate volcanic province from eastern Australia to Zealandia. We model the subducted slab volume over 100 million years and find that slab flux drives volcanic eruption frequency, indicating stimulation of an enriched mantle transition zone reservoir. Volcanic isotope geochemistry allows us to distinguish a high-μ (HIMU) reservoir [>1 billion years (Ga) old] in the slab-poor south, from a northern EM1/EM2 reservoir, reflecting a more recent voluminous influx of oceanic lithosphere into the mantle transition zone. We provide a unified theory linking plate boundary and slab volume reconstructions to upper mantle reservoirs and intraplate volcano geochemistry.

The influence of the relative timing of arterial and subarachnoid space pulse waves on spinal perivascular cerebrospinal fluid flow as a possible factor in syrinx development

2010 ◽  
Vol 112 (4) ◽  
pp. 808-813 ◽  
Author(s):  
Lynne E. Bilston ◽  
Marcus A. Stoodley ◽  
David F. Fletcher
Keyword(s):  
Spinal Cord ◽  
Fluid Flow ◽  
Subarachnoid Space ◽  
Pulse Wave ◽  
Driving Forces ◽  
Fluid Pressure ◽  
Perivascular Spaces ◽  
Relative Timing ◽  
Csf Flow ◽  
Cerebrospinal Fluid Flow

Object The mechanisms of syringomyelia have long puzzled neurosurgeons and researchers alike due to difficulties in identifying the driving forces behind fluid flow into a syrinx, apparently against a pressure gradient between the spinal cord and the subarachnoid space (SAS). Recently, the synchronization between CSF flow and the cardiac cycle has been postulated to affect fluid flow in the spinal cord. This study aims to determine the effect of changes in the timing of SAS pressure on perivascular flow into the spinal cord. Methods This study uses a computational fluid dynamics model to investigate whether the relative timing of a spinal artery cardiovascular pulse wave and fluid pressure in the spinal SAS can influence CSF flow in the perivascular spaces. Results The results show that the mass flow rate of CSF through a model periarterial space is strongly influenced by the relative timing of the arterial pulse wave and the SAS pressure. Conclusions These findings suggest that factors that might alter the timing of the pulse wave or the fluid flow in the SAS could potentially affect fluid flow into a syrinx.

scholarly journals Boninitic blueschists record subduction initiation and subsequent accretion of an arc–forearc in the northeast Proto-Tethys Ocean

Geology ◽  
2021 ◽  
Author(s):  
Dong Fu ◽  
Bo Huang ◽  
Tim E. Johnson ◽  
Simon A. Wilde ◽  
Fred Jourdan ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Plate Tectonics ◽  
Oceanic Lithosphere ◽  
Island Arc ◽  
Early Paleozoic ◽  
Subduction Initiation ◽  
North Qilian Orogenic Belt ◽  
Mariana Arc ◽  
Tethys Ocean ◽  
North Qilian

Subduction of oceanic lithosphere is a diagnostic characteristic of plate tectonics. However, the geodynamic processes from initiation to termination of subduction zones remain enigmatic mainly due to the scarcity of appropriate rock records. We report the first discovery of early Paleozoic boninitic blueschists and associated greenschists from the eastern Proto-Tethyan North Qilian orogenic belt, northeastern Tibet, which have geochemical affinities that are typical of forearc boninites and island arc basalts, respectively. The boninitic protoliths of the blueschists record intra-oceanic subduction initiation at ca. 492–488 Ma in the eastern North Qilian arc/forearc–backarc system, whereas peak blueschist facies metamorphism reflects subsequent subduction of the arc/forearc complex to high pressure at ca. 455 Ma. These relations therefore record the life circle of an intra-oceanic subduction zone within the northeastern Proto-Tethys Ocean. The geodynamic evolution provides an early Paleozoic analogue of the early development of the Izu–Bonin–Mariana arc and its later subduction beneath the extant Japanese arc margin. This finding highlights the important role of subduction of former upper plate island arc/forearcs in reducing the likelihood of preservation of initial subduction-related rock records in ancient orogenic belts.

scholarly journals MAGNETIC CHARACTERISTICS OF METAMORPHIZED ULTRABASITES OF THE OCEANIC LITHOSPHERE

2019 ◽  
Vol 47 (4) ◽  
pp. 106-127
Author(s):  
K. V. Popov ◽  
A. M. Gorodnitskiy ◽  
N. A. Shishkina
Keyword(s):  
World Ocean ◽  
Oceanic Lithosphere ◽  
Structural Features ◽  
Residual Magnetization ◽  
Magnetic Characteristics ◽  
Transform Faults ◽  
Ocean Ridges ◽  
Submarine Ridge ◽  
Deep Layers ◽  
The Stability

As part of the study of the nature of magnetic anomalies associated with the deep layers of the oceanic crust, a comparative analysis was made of the petromagnetic characteristics of serpentinized mantle ultrabasic samples taken from oceanographic expeditions of the Institute of Oceanology and the Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences in various morphotectonic regions of the World Ocean. The purpose of the work is to obtain information on the composition, concentration, crystallization temperature and structural features of ferromagnetic minerals, which are formed in different conditions of the post-magmatic metamorphism of ultrabasites. Sample collections are divided into three groups. 1. Oceanic peridotites from the rift zones of the mid-ocean ridges and transform faults. 2. Peridotites of the submarine ridge Gorringe, located within the Azoro-Gibraltar zone of faults. 3. Dunites of the Pekulney complex (Chukotka) formed in the island arc system. It has been established that in all selected regions, samples of serpentinized hyperbasites have high values of natural residual magnetization, magnetic susceptibility and saturation magnetization. The highest values of magnetic parameters are the dunites of the Pekulney complex. Estimation of the dependence of the concentration of ferrimagnetic materials C% of the degree of serpentinization of the SS%. showed that it is practically of little significance. The main factors contributing to the increase in the concentration of magnetite are the increased iron content of olivine in ultrabasites and the temperature of metamorphism. The question of the period of formation of magnetites and the stability of their primary residual magnetization requires further study.

scholarly journals The Birth, Growth, and Death of Continents

Eos ◽  
2021 ◽  
Vol 102 ◽  
Author(s):  
Rixiang Zhu ◽  
Guochun Zhao ◽  
Wenjiao Xiao ◽  
Ling Chen ◽  
Yanjie Tang
Keyword(s):  
Plate Tectonics ◽  
Driving Forces

There are various explanations for how the Earth’s continents form, develop, and change but challenges remain in fully understanding the driving forces behind plate tectonics on our planet.

scholarly journals GEODYNAMICS

GEODYNAMICS ◽  
2011 ◽  
Vol 2(11)2011 (2(11)) ◽  
pp. 315-316
Author(s):  
V. V. Furman ◽  
◽  
M. M. Khomiak ◽  
Keyword(s):  
Finite Element ◽  
Numerical Modelling ◽  
Thin Plate ◽  
Thermal Convection ◽  
Plate Tectonics ◽  
Driving Forces ◽  
Finite Element Approach ◽  
Earth’S Mantle ◽  
Elastic Thin Plate ◽  
Element Approach

Thermal convection in Earth’s mantle are driving forces of plate tectonics. Combine model –viscous uncompressed mantle and thermo-elastic thin plate – is developed. The finite element approach in numerical modelling of geodynamical processes is presented.

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