scholarly journals Extinct Style of Plate Tectonics Explains Early Earth’s Flat Mountains

Eos ◽  
2021 ◽  
Vol 102 ◽  
Author(s):  
Becca Dzombak
Keyword(s):  
Crustal Deformation ◽  
Plate Tectonics ◽  
Geologic Record ◽  
Thin Crust

The geologic record suggests that despite Earth’s hot, thin crust during the Proterozoic, mountains were still able to form thanks to an extinct style of crustal deformation.

The Biography of the Earth

2021 ◽  
pp. 163-180
Author(s):  
Elisabeth Ervin-Blankenheim
Keyword(s):  
Early Life ◽  
Plate Tectonics ◽  
Life Forms ◽  
Snowball Earth ◽  
The Moon ◽  
Geologic Time ◽  
Earth Systems ◽  
Organic Life ◽  
The Earth ◽  
Geologic Record

The way the planet has changed through geologic time, and life on it, the account of the Earth, is the topic of this and the next three chapters, starting in this chapter with the Precambrian Supereon. The overarching principles of geologic time, plate tectonics, and evolution worked dynamically to create the biography of the planet. This chapter traces back to the recesses of the geologic record and early Earth, from its birth and the formation of the Moon through seven-eighths of its existence, a huge span of time. Early life forms emerged during this supereon in the Archean Eon and had a profound influence on other Earth systems. Life interacted and changed the chemistry of the atmosphere through photosynthesis, so much so that the changes are thought to have sent planetary systems over an edge into multiple “Snowball Earth” episodes when most of the planet froze over. In addition to the beginning of organic life and climate, the emergence and configuration of the continents during the Precambrian are covered. Events of this supereon set the stage for the burgeoning of life forms in the next eon, the Phanerozoic.

scholarly journals Global tectonic evolution of Venus, from exogenic to endogenic over time, and implications for early Earth processes

2018 ◽  
Vol 376 (2132) ◽  
pp. 20170412 ◽  
Author(s):  
Vicki L. Hansen
Keyword(s):  
Tectonic Evolution ◽  
Plate Tectonics ◽  
Heat Budget ◽  
Apparent Paradox ◽  
Tectonic Processes ◽  
Analogue Models ◽  
Flow Processes ◽  
Geologic Record ◽  
Earth Dynamics ◽  
Unique Surface

Venus provides a rich arena in which to stretch one's tectonic imagination with respect to non-plate tectonic processes of heat transfer on an Earth-like planet. Venus is similar to Earth in density, size, inferred composition and heat budget. However, Venus' lack of plate tectonics and terrestrial surficial processes results in the preservation of a unique surface geologic record of non-plate tectonomagmatic processes. In this paper, I explore three global tectonic domains that represent changes in global conditions and tectonic regimes through time, divided respectively into temporal eras. Impactors played a prominent role in the ancient era, characterized by thin global lithosphere. The Artemis superstructure era highlights sublithospheric flow processes related to a uniquely large super plume. The fracture zone complex era, marked by broad zones of tectonomagmatic activity, witnessed coupled spreading and underthrusting, since arrested. These three tectonic regimes provide possible analogue models for terrestrial Archaean craton formation, continent formation without plate tectonics, and mechanisms underlying the emergence of plate tectonics. A bolide impact model for craton formation addresses the apparent paradox of both undepleted mantle and growth of Archaean crust, and recycling of significant Archaean crust to the mantle. This article is part of a discussion meeting issue ‘Earth dynamics and the development of plate tectonics’.

Did plate tectonics shutdown in the Palaeoproterozoic? A view from the Siderian geologic record

2014 ◽  
Vol 26 (3-4) ◽  
pp. 803-815 ◽  
Author(s):  
Sally J. Pehrsson ◽  
Kenneth L. Buchan ◽  
Bruce M. Eglington ◽  
Robert M. Berman ◽  
Robert H. Rainbird
Keyword(s):  
Plate Tectonics ◽  
Geologic Record

scholarly journals How isostasy explains continental rifting in East Africa?

2020 ◽  
Author(s):  
Mohammad Bagherbandi ◽  
Nureldin A. A. Gido
Keyword(s):  
East Africa ◽  
Rift Valley ◽  
Plate Tectonics ◽  
Gravity Data ◽  
Density Contrast ◽  
Earthquake Activity ◽  
Continental Rifting ◽  
The Earth ◽  
Geodynamic Processes ◽  
Thin Crust

<p>The principle of isostasy plays an important role to understand the relation between different geodynamic processes. Although, it is difficult to find an exact method that delivers a complete image of the Earth structure. However, gravimetric methods are alternative to provide images of the interior of the Earth. The Earth’s crust parameters, i.e. crustal depth and crust-mantle density contrast, can reveal adequate information about the solid Earth system such as volcanic activity, earthquake and continental rifting. Hence, in this study, a combine Moho model using seismic and gravity data is determined to investigate the relationship between the isostatic state of the lithosphere and seismic activities in East Africa. Our results show that isostatic equilibrium and compensation states are closely correlated to the seismicity patterns in the study area. For example, several studies suggest that African superplume causes the rift valley, and consequently differences in crustal and mantle densities occur. This paper presents a method to determine the crustal thickness and crust-mantle density contrast and consequently one can observe low-density contrast (about 200 kg/m<sup>3</sup> ) and thin crust (about 30 km) near the triple junction plate tectonics in East Africa (Afar Triangle), which confirms the state of overcompensation in the rift valley areas. Furthermore, the density structure of the lithosphere shows a large correlation with the earthquake activity, sub-crustal stress and volcanic distribution across East Africa.</p>

Introduction

2021 ◽  
pp. 1-5
Author(s):  
Elisabeth Ervin-Blankenheim
Keyword(s):  
Plate Tectonics ◽  
Global Climate ◽  
Life Forms ◽  
Geologic Time ◽  
The Earth ◽  
History Of ◽  
Geologic Record ◽  
Shed Light ◽  
Geologic Processes

Geology offers a unique perspective on the Earth—past, present, and future. It is the language through which the Earth speaks, by means of rocks, geologic processes, the geologic record, and the biography of the Earth. This book explains how geologists arrived at understanding the story of the planet and discusses the three major tenets of geology: geologic time, plate tectonics, and evolution. The development of theories about how the Earth functions is detailed, along with their relevance. Within geology are the keys to understanding the history of the Earth, how that past informs the present, and ways of going forward. The Earth has interacted with life as long as that life has been extant. Life has shaped the Earth and vice versa with times of flowering and the radiation of life forms and other times of extinctions through profound changes in the climate and positions of the continents. These dynamics can shed light on the current changes in and consequences of perturbing the global climate.

John Tuzo Wilson: a Canadian who revolutionized Earth Sciences

2014 ◽  
Vol 51 (3) ◽  
pp. v-viii ◽  
Author(s):  
Ali Polat
Keyword(s):  
Earth Sciences ◽  
Plate Tectonics ◽  
50Th Anniversary ◽  
Continental Drift ◽  
Special Issue ◽  
The Past ◽  
The Earth ◽  
The World ◽  
Wilson Cycle ◽  
Geologic Record

John Tuzo Wilson (1908–1993) was one of the greatest Canadian scientists of the 20th century. His contributions to Earth Sciences, leading the formulation of the theory of plate tectonics, have revolutionized our understanding of how the planet Earth works and evolved over the past 4 billion years. This 50th anniversary special issue of the Canadian Journal of Earth Sciences is dedicated in honour of John Tuzo Wilson, who inspired tens of thousands of students all around the world to study the Earth. This special issue contains 12 papers dealing with various aspects of the “Wilson Cycle” in the geologic record, plate tectonics, mantle plumes, and how John Tuzo Wilson accepted “continental drift” and formulated the theory of plate tectonics. The contributions have mostly been made by geoscientists who directly or indirectly associated with John Tuzo Wilson and have contributed significantly to the plate tectonics paradigm.

Atmospheric carbon dioxide and the long-term control of the Earth's climate

1995 ◽  
Vol 13 (7) ◽  
pp. 782-790 ◽  
Author(s):  
J. H. Carver ◽  
I. M. Vardavas
Keyword(s):  
Atmospheric Carbon Dioxide ◽  
Plate Tectonics ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
The Sun ◽  
Model Calculations ◽  
Co2 Level ◽  
Earth’S Climate ◽  
Outgassing Rate ◽  
Geologic Record

Abstract. A CO2-weathering model has been used to explore the possible evolution of the Earth's climate as the Sun steadily brightened throughout geologic time. The results of the model calculations can be described in terms of three, qualitatively different, "Megaclimates". Mega-climate 1 resulted from a period of rapid outgassing in the early Archean, with high, but declining, temperatures caused by the small weathering rates on a largely water-covered planet. Mega-climate 2 began about 3 Gyear ago as major continental land masses developed, increasing the weathering rate in the early Proterozoic and thereby depleting the atmospheric CO2 concentration. This process produced the first Precambrian glaciations about 2.3 Gyear ago. During Mega-climate 2, evolutionary biological processes increased the surface weatherability in incremental steps and plate tectonics modulated the CO2 outgassing rate with an estimated period of 150 Myear (approximately one-half the period for the formation and breakup of super continents). Throughout Mega-climate 2 the surface temperature was controlled by variations in the atmospheric CO2 level allowing transitions between glacial and non-glacial conditions. The results of the model for Mega-climate 2 are in agreement with the occurrence (and absence) of glaciations in the geologic record. Extending the model to the future suggests that CO2 control of the Earth's temperature will no longer be able to compensate for a solar flux that continues to increase. The present level of atmospheric CO2 is so small that further reduction in CO2 cannot prevent the Earth from experiencing Mega-climate 3 with steadily increasing surface temperatures caused by the continued brightening of the Sun. During Mega-climate 3, the main danger to the biosphere would come not from an increasing temperature but from a decreasing (rather than an increasing) CO2 level which could, in time, fall below 0.5 PAL, causing serious damage to the biosphere. Fortunately, the rates of change due to solar brightening are slow enough that Mega-climate 3 appears to pose no threat to the biosphere for the next 0.5-2 Gyear.

Occurrence and biogeographic significance of Heliaster (Echinodermata: Asteroidea) from the Pliocene of southwest Florida

1988 ◽  
Vol 62 (01) ◽  
pp. 126-132 ◽  
Author(s):  
Douglas S. Jones ◽  
Roger W. Portell
Keyword(s):  
Central American ◽  
Eastern Pacific ◽  
Whole Body ◽  
Marine Fauna ◽  
Western Atlantic ◽  
Southwest Florida ◽  
Extant Species ◽  
Geologic Record ◽  
Central American Isthmus

Whole body asteroid fossils are rare in the geologic record and previously unreported from the Cenozoic of Florida. However, specimens of the extant species,Heliaster microbrachiusXantus, were recently discovered in upper Pliocene deposits. This marks the first reported fossil occurrence of the monogeneric Heliasteridae, a group today confined to the eastern Pacific. This discovery provides further non-molluscan evidence of the close similarities between the Neogene marine fauna of Florida and the modern fauna of the eastern Pacific. The extinction of the heliasters in the western Atlantic is consistent with the pattern of many other marine groups in the region which suffered impoverishment following uplift of the Central American isthmus.

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