ROCK AND MINERALS

The Earth cools and the first ocean is formed.

1996

Tectonics and climate are both directly and indirectly related. The direct connection is between uplift, atmospheric circulation, and the hydrologic cycle. The indirect links are via subduction, volcanism, the introduction of gasses into the atmosphere, and through erosion and consumption of atmospheric gases by chemical weathering. Rifting of continental blocks involves broad upwarping followed by subsidence of a central valley and uplift of marginal shoulders. The result is an evolving regional climate which has been repeated many times in the Phanerozoic: first a vaportrapping arch, followed by a rift valley with fresh-water lakes, culminating in an arid rift bordered by mountains intercepting incoming precipitation. Convergence tectonics affects climate on a larger scale. A mountain range is a barrier to atmospheric circulation, especially if perpendicular to the circulation. It also traps water vapor converting latent to sensible heat. Broad uplift results in a shorter path for both incoming and outgoing radiation resulting in seasonal climate extremes with reversals of atmospheric pressure and enhanced monsoonal circulation. Volcanism affects climate by introducing ash and aerosols into the atmosphere, but unless these are injected into the stratosphere, they have little effect. Stratospheric injection is most likely to occur at high latitudes, where the thickness of the troposphere is minimal. Volcanoes introduce CO 2 , a greenhouse gas, into the atmosphere. Geochemical effects of tectonic uplift and unroofing relate to the weathering of silicate rocks, the means by which CO 2 is removed from the atmosphere-ocean system on long-term time scales.

2017

The Earth's climate is influenced by many factors, including solar radiation, wind, and ocean currents. Researchers try to integrate all of these influencing variables into their models. Many of the processes involved are now well understood. But interaction among the various factors is very complex and numerous questions remain unresolved. The Earth's climate has changed throughout history. Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 7,000 years ago marking the beginning of the modern climate era-and of human civilization. Most of these climate changes are attributed to very small variations in Earth's orbit that change the amount of solar energy our planet receives.

OPEC Review, 1993

AT A TIME of so much discussion about current and future climate change, little attention is being paid to the situation in the past. The aim of this paper is, therefore, to shed some light on the past climate of the Earth, as well as on present and expected future changes. This, in my opinion, is essential, since the present climate is a natural extension of that of the past and the causes of climate variation may be very much interrelated. Full understanding of present and future climate change can only be explained if past climate behaviour is fully understood. Climate change may be defined as the variations in the components of the climate which may lead to its warming or cooling. These components are: the atmosphere, the hydrosphere, the cryosphere, the biosphere and the lithosphere, forming what is known as the 'climate system'. These climate elements vary through time as well as from one region to another. Indirect evidence of climate variation during geological time is revealed in rocks, fossils, lake and ocean beds, glacial deposits, peat bogs and soils. The widths of annual growth rings in trees correlate with temperature and rainfall fluctuations, and fossil trees provide records of dramatic climatic events in the past. Archaeological remains and written history offer clues to climate conditions and variations during the human era. More recently, modem instrument records have provided direct evidence of climate change. Many theories have been put forward to explain the causes of climate change, such as changes in the atmosphere's content, veations in the Earth's surface features, changes in solar radiation (insolation) patterns and human interference. Variations in the amount and distribution of gases, clouds and solid particles within the atmosphere may lead to changes in the climate. Natural phenomena, such as volcanic eruptions, comet and/or large meteor impacts, may cause such changes. The Earth's surface has a direct influence on the heat and moisture of the climate. Paleoclhatic changes have been attributed to changes in the position, size The author is Head, Energy Section, in the Energy Studies Department at the OPEC Secretariat in Vienna, Austria. The original manuscript was received on 23 April 1993; a shorter version of the paper was published in the April I993 issue of the OPEC Bulletin. 1. The geological record on climate Geological time is divided into four major units (eras): the Re-Cambrian; the Palaeozoic; the Mesozoic; and the Cenozoic. These four eras are subdivided into *nods, and the periods in turn are subdivided into epochs. Using the geological concept that "the present is the key to the past", and by studying present-day sediments and their related environments, one can, in a similar manner, analyze past sedimentary records and try to infer the ancient environments which led to the deposition of particular types of sediment. Therefore, deductions can be made about the climatic significance of certain classes of sedimentary rock, such as: Calcareous rock (limestones, marbles and marls). These are currently deposited in warm, temperate or tropical seas. Coral reefs which belong to this category of rocks are currently confined to subtropical shorelines, typically in the 20-25OC sea temperature range, and to waters with a salinity of 2.74.0 per cent. 306 OPEC Review Arenaceous rocks (sands, sandstones, quartzites and conglomerates). These rocks are rich in silica and are often made up of fragments of preexisting rocks, implying the breakdown of continental surfaces by processes of rapid denudation, which indicates the washing away of the covering of strata by rapid water action (heavy rainfall or river action or both). Carbonaceous rocks (coals, oil-and gas-bearing rocks). Coal, oil and gas are derived from organic material (plants and/or animals); therefore, their presence inzhe geological record could indicate the distribution of land forests and the reduction of the marine environment in which the hydrocarbons were formed. Evaporites (salt, potash, gypsum and anhydrite). Accumulations of such material indicates rapid evaporation in deserts, shorelines and inland basins. Glacial deposits (till, moraine, diamictites and outwash fans). Sea and lake ice may raft boulders and other coarse material, like till or ground moraine (unsorted assemblages of pebbles and boulders that are typically 'unrounded' by water transport and are embedded in a clay or silt matrix), away from their original place, finally depositing them in the new location where the ice melts. Glacial deposits indicate cold climates in the regions in which they are found. Other deposits, like red beds (assemblages of red and yellow sandstones, marls, clays, pebble and boulder beds). Their presence implies, as from their colour (abundant iron oxide), warm desert conditions or, sometimes, warm, humid conditions with an abundance of oxygen. 2. Climate during geological time Based on the information obtained from the sedimentary record, the following conclusions may be drawn about climate variations during the various geological periods (figure 1 and table A1 in the annex). 2.1 The climate of the pre-Cambrian era This era covered the time period from 590 to 5,000 million years ago. The climate during this era is characterized by much warmer conditions than at present, an abundance of carbon dioxide (CO2), a lack of oxygen and hence the presence of ozone in the atmosphere, powerful ultraviolet radiation at the Earth's surface, which inhibited terrestial life and stimulated active chemical reactions in the lower Autumn 1993 2.4 The climate of Cenozoic era This era extends from 65m years ago to the present. Its climate during the Tertiary period (2-65m years ago) was characterized by: warm and fairly moist Autumn 1993

2023

Springer eBooks, 1991

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An emerging challenge for understanding the Earth system is to determine the relative roles of early planetary processes versus progressive differentiation in shaping the Earth's chemical architecture. An enduring tenet of modern chemical geodynamics is that the Earth started as a well-mixed and homogeneous body which evolved progressively over the geologic time to several chemically distinct domains. As a consequence, the observable chemical heterogeneity in mantle-derived rocks has generally been attributed to the Earth's dynamic evolution over the past 4.5 Ga. However, the identification of chemical heterogeneity formed during the period 4.53-4.45 Ga in the ca. 60 Ma Baffin Bay high-magnesium lavas provides strong evidence that chemical effects of early differentiation can persist in mantle reservoirs to the present day. Here, we demonstrate that such an ancient mantle reservoir is likely composed of enriched and depleted dense melts, and propose a model for early global differentiation of the bulk silicate Earth that would produce two types of dense melts with distinctive chemical compositions in the deep Earth. These dense melts ultimately became parts of the thermo-chemical piles near the coremantle boundary that have been protected from complete entrainment by subsequent mantle convection currents. We argue that although such dense melts likely exhibit some 'primordial' geochemical signatures, they are not representative of the bulk silicate Earth. Our work provides a strong case for the mantle chemical heterogeneity being formed by a major differentiation event shortly after planet accretion rather than through the subsequent geodynamic evolution.

Thermal Science

Global warming and other climate change phenomena became a worldwide exploited subject over recent decades. World science has made enormous progress in understanding past climate change and its causes, and continues to study current and potential impacts that will affect people in the future. All scientists agree that the Earth's climate is changing due to natural phenomena, and most of them argue that human activities are increasing the greenhouse effect, while some scientists attribute climate changes exclusively to the natural causes. Though there still is, and always will be, need for multiple lines of research on an extremely complex system like Earth's climate is, an immediate consensus is crucial for decision-makers to place climate change in the context of other large challenges facing the world today. This paper discusses the existing body of evidence on climate changes in the past, and uncertainties that prevent scientists to reach full consensus on how climate mig...

Journal of Energy - Energija

The present work includes the coupled electromagnetic/thermal analysis of a threephase system composed of three single-core cables in trefoil configuration. The cable system is analyzed in thermally stationary and non-stationary state, taking into account the non-linearity of heat conduction in the soil surrounding the cable. The complex model of heat transfer in soil, caused by soil drying in the cable’s surrounding, has been made by applying two zones of different heat conductions.