نتایج جستجو برای: volcanism
تعداد نتایج: 2423 فیلتر نتایج به سال:
Decades of space exploration reveal that Mars has been reshaped by volcanism throughout its history. The range observed volcanic landforms shows effusive and explosive eruptions have occurred, albeit unevenly in time space. Evidence for volcanism—characterized as which magma is disrupted the expansion dissolved gases or an interaction with external volatiles—is less common than evidence activit...
Uranium-lead data indicate that the high-pressure granulitic and charnockitic nuclei within the medium-grade metamorphic complex of the Peruvian coastal area must be related to an orogenic event 2 x 10(9) years ago. As in western Africa and Brazil, this old granulitic basement is reworked by Late Precambrian orogeny. Its presence along the Peru-Chile Trench must be taken into account in interpr...
The Gruithuisen and Mairan domes on the moon represent morphologically and spectrally distinct nonmare extrusive volcanic features of Imbrian age. The composition, morphology, and age relationships of the domes indicate that nonmare extrusive volcanism in the northern Procellarum region of the moon continued until about 3.3 x 10(9) to 3.6 x 10(9) years ago and was partially contemporaneous with...
www.sciencemag.org SCIENCE VOL 323 13 FEBRUARY 2009 843 COVER An image of Mare Moscoviense on the lunar farside, taken by the Terrain Camera aboard the SELENE (Kaguya) spacecraft on 17 January 2008. Crater frequency distributions derived from such images yield ages of about 2.5 billion years for several volcanic deposits in this mare, indicating that volcanism on the lunar farside lasted about ...
Tectonics, volcanism, and climate on Venus may be strongly coupled. Large excursions in surface temperature predicted to follow a global or near-global volcanic event diffuse into the interior and introduce thermal stresses of a magnitude sufficient to influence widespread tectonic deformation. This sequence of events accounts for the timing and many of the characteristics of deformation in the...
[1] We examine the relationship between the GISP2 dust profile, a proxy for the Northern Hemisphere atmospheric dust load, and the Wolf sunspot number, a proxy for solar activity. The two records are positively correlated, but the phase of the relationship is disturbed by the effects of explosive volcanism. Similar correlation failures have already been noted for many other climatic indicators....
In a previous paper ' the writers suggested that some rexplosion structures currently attributed to volcanism may actually record impacts of giant meteorites which fell during the geological past. It is the purpose of this article to show how meteorite craters and th eir underlying structures might be preserved, and to evaluate the meteoritic hypothesis as an 'explanativn for three structures w...
www.sciencemag.org SCIENCE VOL 323 13 FEBRUARY 2009 843 COVER An image of Mare Moscoviense on the lunar farside, taken by the Terrain Camera aboard the SELENE (Kaguya) spacecraft on 17 January 2008. Crater frequency distributions derived from such images yield ages of about 2.5 billion years for several volcanic deposits in this mare, indicating that volcanism on the lunar farside lasted about ...
Introduction: The lower crust of the Moon remains a critical unknown for models of lunar compositional mass balance and for models of petrogenesis of lunar rock types. Key questions addressed here are (1) how mafic are the rocks of the lower crust and (2) are they ferroan or magnesian? Answers to these questions bear on the concentration and distribution of radiogenic heat-producing elements an...
We present a climatological model of the extinction coefficient of stratospheric aerosols in the UV-visible range based on SAGE II data. The model is a function of wavelength, latitude, relative altitude with respect to the tropopause and depends on the volcanism level. The vertical structure describes the tropopause region, the Junge layer and the high altitude domain. The model is shown to pr...
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