نتایج جستجو برای: earth crust
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The deposits of hydrocarbons in the crust of the Earth have long been regarded by many investigators as deriving from materials incorporated in the mantle at the time of the Earth's formation. Outgassing processes, active in all geological epochs, then transported the liquids and gases liberated there into porous rocks of the crust. The alternative viewpoint, that biological debris was the sour...
Measurable variations in (182)W/(183)W, (142)Nd/(144)Nd, (129)Xe/(130)Xe and (136)XePu/(130)Xe in the Earth and meteorites provide a record of accretion and formation of the core, early crust and atmosphere. These variations are due to the decay of the now extinct nuclides (182)Hf, (146)Sm, (129)I and (244)Pu. The (l82)Hf-(182)W system is the best accretion and core-formation chronometer, which...
Recent 142Nd isotope data indicate that the silicate Earth has an Sm/Nd ratio greater than the supposed chondritic building blocks of the planet. This elevated Sm/Nd has been ascribed either to a “hidden” reservoir in the Earth1,2 or to loss of an early-formed terrestrial crust by impact ablation3. Since removal of crust by ablation would also remove the heat producing elements, K, U and Th, th...
The lunar crust provides a record of the planetary formation and early evolutionary processes and contains a wealth of information about the origin and evolution of the Earth-Moon system (e.g., Taylor 1982; NRC 2007; Canup 2008, 2012; Cuk and Stewart 2012; Young et al. 2016). Understanding these processes is crucial for the reconstruction of the early evolutionary stages of the Earth, e.g., the...
The Earth's engine is driven by unknown proportions of primordial energy and heat produced in radioactive decay. Unfortunately, competing models of Earth's composition reveal an order of magnitude uncertainty in the amount of radiogenic power driving mantle dynamics. Recent measurements of the Earth's flux of geoneutrinos, electron antineutrinos from terrestrial natural radioactivity, reveal th...
[1] Subduction zones are where sediments, oceanic crust, and mantle lithosphere return to and reequilibrate with Earth’s mantle. Subduction zones are interior expressions of Earth’s 55,000 km of convergent plate margins and are the geodynamic system that builds island arcs. Excess density of the mantle lithosphere in subduction zones provides most of the power needed to move the plates while in...
Critical to the origin of life are the ingredients of life, of course, but also the physical and chemical conditions in which prebiotic chemical reactions can take place. These factors place constraints on the types of Hadean environment in which life could have emerged. Many locations, ranging from hydrothermal vents and pumice rafts, through volcanic-hosted splash pools to continental springs...
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