نتایج جستجو برای: volcanism
تعداد نتایج: 2423 فیلتر نتایج به سال:
[1] A comparison of time series of basaltic and silicic eruptions in eastern California over the last 400 kyr with the contemporaneous global record of glaciation suggests that this volcanism is influenced by the growth and retreat of glaciers occurring over periods of about 40 kyr. Statistically significant cross correlations between changes in eruption frequency and the first derivative of th...
Understanding the causes and timings of mass extinctions are important for our understanding of the evolution of life on Earth and how major biogeochemical cycles have been and can be perturbed. Four of the five biggest mass extinctions (1) are associated with large igneous provinces (LIPS), which are the most voluminous volcanic events on Earth, but whether LIPS triggered the extinctions is di...
Massive continental volcanism and/or bolide impacts are considered by many authors to have caused three major mass extinction events during the last 300 million years: the end-Permian, end-Cretaceous and end-Triassic extinctions. However, reevaluation of the frequency of bolide impacts and plume-related flood basalt provinces indicates that both types of event occur much more frequently than ma...
Cryptomaria, lunar volcanic deposits obscured by crater and basin impact ejecta, can provide important information about the thermal and volcanic history of the Moon. The timing of cryptomare deposition has implications for the duration and flux of mare basalt volcanism. In addition, knowing the distribution of cryptomaria can provide information about mantle convection and lunar magma ocean so...
Analyzing data from our optical dust logger, we find that volcanic ash layers from the Siple Dome (Antarctica) borehole are simultaneous (with >99% rejection of the null hypothesis) with the onset of millennium-timescale cooling recorded at Greenland Ice Sheet Project 2 (GISP2; Greenland). These data are the best evidence yet for a causal connection between volcanism and millennial climate chan...
Three voluminous rhyolitic ignimbrites have been identified along the southern margin of the central Snake River Plain. As a result of wide-scale correlations, new volume estimates can be made for these deposits: ~350 km for the Steer Basin Tuff and Cougar Point Tuff XI, and ~1,000 km for Cougar Point Tuff XIII. These volumes exclude any associated regional ashfalls and correlation across to th...
Geological mapping and establishment of stratigraphic relationships provides an overview of geological processes operating on Mars and how they have varied in time and space. Impact craters and basins shaped the crust in earliest history and as their importance declined, evidence of extensive regional volcanism emerged during the Late Noachian. Regional volcanism characterized the Early Hesperi...
Submarine volcanism represents ~80% of the volcanic activity on Earth and is an important source of mantle-derived gases. These gases are of basic importance for the comprehension of mantle characteristics in areas where subaerial volcanism is missing or strongly modified by the presence of crustal/atmospheric components. Though, the study of submarine volcanism remains a challenge due to their...
The core-mantle boundary region is often considered to be the source of narrow upwellings which drive or influence plate motions and continental breakup, fuel large igneous provinces and generate volcanic chains. The plume hypothesis has influenced most fields of geochemistry, petrology, geodynamics and mantle evolution. The key axioms underlying the plume paradigm are identified: Axioms are se...
Origin of Lunar Basalts: A Geophysical Interpretation J. Arkani-Hamed Lunar Pyroclastic Soils of the Apollo 17 Double Drive Tube 74001/2 A. Basu, D. S. McKay, and S. J. Wentworth Lunar Explosive Volcanism: The Remote Sensing Perspective C. R. Coombs and B. R. Hawke The Optimal Lunar Resource: Ilmenite-rich Regional Pyroclastic Deposits C. R. Coombs, B. R. Hawke, and B. Clark Pyroclastic Volcani...
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