A Tectonically-Controlled Rock Cycle

History of Geo- and Space Sciences, 2022

The archetype of a cycle has played an essential role in explaining observations of nature over thousands of years. At present, this perception significantly influences the worldview of modern societies, including several areas of science. In the Earth sciences, the concept of cyclicity offers simple analytical solutions in the face of complex events and their respective products, in both time and space. Current stratigraphic research integrates several methods to identify repetitive patterns in the stratigraphic record and to interpret oscillatory geological processes. This essay proposes a historical review of the cyclic conceptions from the earliest phases in the Earth sciences to their subsequent evolution into current stratigraphic principles and practices, contributing to identifying opportunities in integrating methodologies and developing future research mainly associated with quantitative approaches.

2021

The archetype of a cycle has played an essential role in explaining observations of nature over thousands of years. At present, this perception significantly influences the worldview of modern societies, including several areas of science. In Earth sciences, the concept of cyclicity offers simple analytical solutions in the face of complex events and their respective products, both in time and space. Current stratigraphic research integrates several methods to identify repetitive patterns in the stratigraphic record and to interpret oscillatory geological processes. This essay proposes a historical review of the cyclic conceptions from the earliest phases in Earth sciences to their subsequent evolution into current stratigraphic principles and practices, contributing to identifying opportunities in integrating methodologies and developing future research mainly associated with quantitative approaches. Nature vibrates with rhythms, climatic and dystrophic, those finding stratigraphic expression ranging in period from the rapid oscillation of surface waters, recorded in ripple-marks, to those long-deferred stirrings of the deep imprisoned titans which have divided earth history into periods and eras. The flight of time is measured by the weaving of composite rhythms-day and night, calm and storm, summer and winter, birth

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Geological Society of America Bulletin, 2009

Relations among ages and present areas of exposure of volcanic, sedimentary, plutonic, and metamorphic rock units (lithosomes) record a complex interplay between depths and rates of formation, rates of subsequent tectonic subsidence and burial, and/or rates of uplift and erosion. Thus, they potentially serve as effi cient deep-time geologic speedometers, providing quantitative insight into rates of material transfer among the principal rock reservoirs-processes central to the rock cycle. Areal extents of lithosomes exposed on all continents from two map sources Geological Survey of Canada [GSC] and the Food and Agricultural Organization [FAO] of the United Nations Educational, Scientifi c, and Cultural Organization [UNESCO]) indicate that volcanic, sedimentary, plutonic, and metamorphic rocks occupy ~8%, 73%, 7%, and 12% of global exposures, respectively.

Physics of the Earth and Planetary Interiors, 1997

The evolution of the Earth is characterized by irreversible processes: radioactive decay of the major heat-producing elements, thermal convection and chemical segregation. The prevailing heating from within and the temperature dependence of the viscosity are essential for thermal convection. In the present paper, the chemical and thermal evolution of the mantle and the generation of the continent material are represented by a two-dimensional and finite-difference Boussinesq convection model. We have incorporated the above-mentioned principal features in this model, a geochemical paper by Hofmann (1988, Earth Planet. Sci. Lett., 90: 297-314) constituting our starting point for the distribution of the radionuclides. The concentration of the radionuclides and the viscosity are functions of the location and time developing according to our system of differential equations. Although the real Earth is a much more complex system, we have dared to make a comparison with observed geophysical and geological data; we obtain a depleted upper mantle and acceptable values for the heat flow on the surface of the Earth as well as for the distribution of temperature, viscosity and of the velocity of creep in the mantle. The ups and downs of the convective vigour of the model roughly resemble the supercontinental cycles, the world-wide distribution of mineral dates in time, the sea-level variations and the variations of a number of geochemical parameters. © 1997 Elsevier Science B.V. * Corresponding author. are formed, interrupted by more quiescent periods. Very similar curve behaviours have been obtained by modem workers, e.g. . It is fair to assume that there must be a link between the chemical segregation leading to the formation of continental crest material, the recycling (anatexis) of granitic and granodioritic material and thermal mantle convection. In looking for such a link, we proceed from the assumption that the endothermic spinel-perovskite phase change at 670 kin depth is promoting a two-layer convection state in the mantle. This means that we want to show with our model calculations that these episodes of enhanced magmatism and orogeny may be explained even if convective mantle avalanches (Machetel and Weber, 1991; Tackley et 0031-9201/97/$17.00

2017

Lecture Notes in Earth Sciences, 2003

The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use Typesetting: Camera ready by editors Printed on acid-free paper 3213 141 -5 4 3 2 1 0 Preface In many aspects science becomes conducted nowadays through technology and preferential criteria of economy. Thus investigation and knowledge is evidently linked to a specific purpose. Especially Earth science is confronted with two major human perspectives concerning our natural environment: sustainability of resources and assessment of risks. Both aspects are expressing urgent needs of the living society, but in the same way those needs are addressing a long lasting fundamental challenge which has so far not been met. Following on the patterns of economy and technology, the key is presumed to be found through a development of feasible concepts for a management of both our natural environment and in one or the other way the realm of life. Although new techniques for observation and analysis led to an increase of rather specific knowledge about particular phenomena, yet we fail now even more frequently to avoid unforeseen implications and sudden changes of a situation. Obviously the improved technological tools and the assigned expectations on a management of nature still exceed our traditional scientific experience and accumulated competence. Earth-and Life-Sciences are nowadays exceedingly faced with the puzzling nature of an almost boundless network of relations, i. e., the complexity of phenomena with respect to their variability. The disciplinary notations and their particular approaches are thus no longer accounting sufficiently for the recorded context of phenomena, for their permanent variability and their unpredictable implications. The large environmental changes of glacial climatic cycles, for instance, demonstrate this complexity of such a typical phenomenology. Ice age cycles involve beside the reorganisation of ice sheets as well changes of the ocean-atmosphere system, the physics and chemistry of the oceans and their sedimentary boundaries. They are linked to the carbon cycle, and the marine and terrestrial ecosystems and last not least the crucial changes in the orbital parameters such as in eccentricity, precession frequency and tilt of the planet during its rotation and movement in space. So far changes of solar radiation through the activity of the sun itself have not yet been adequately incorporated. The entire dynamics of the climate system has therefore the potential to perform abrupt reorganisation as demonstrated by sedimentary records. It becomes quite obvious, in order to reveal the complex nature of phenomena we evidently have to reorganise our own scientific perspectives and our disciplinary bounds as well.

Earth and Planetary Science Letters, 1993

Published data sets of major geologic events of the past ~ 250 Myr (extinction events, sea-level lows, continental flood-basalt eruptions, mountain-building events, abrupt changes in sea-floor spreading, ocean-anoxic and blackshale events and the largest evaporite deposits) have been synthesized (with estimated errors). These events show evidence for a statistically significant periodic component with an underlying periodicity, formally equal to 26.6 Myr, and a recent maximum, close to the present time. The cycle may not be strictly periodic, but a periodicity of ~ 30 Myr is robust to probable errors in dating of the geologic events. The intervals of geologic change seem to involve jumps in sea-floor spreading associated with episodic continental rifting, volcanism, enhanced orogeny, global sea-level changes and fluctuations in climate. The period may represent a purely internal earth-pulsation, but evidence of planetesimal impacts at several extinction boundaries, and a possible underlying cycle of 28-36 Myr in crater ages, suggests that highly energetic impacts may be affecting global tectonics. A cyclic increase in the flux of planetesimals might result from the passage of the Solar System through the central plane of the Milky Way Galaxy-an event with a periodicity and mean phasing similar to that detected in the geologic changes.

Geosphere, 2007

Modern earth science pedagogy is increasingly based on an integrated systems framework, where all of the major earth systems, including lithospheric cycles, are interlinked and dependent on each other through feedback loops. Most secondary school and introductory college-...

Physics of the Earth and Planetary Interiors, 2008

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