نتایج جستجو برای: Pyroclastic units

تعداد نتایج: 172732  

2002
RAY HAWKE

Mantling deposits on the Moon are considered to be pyroclastic units emplaced on the lunar surface as a result of explosive fire fountaining. These pyroclastic units are characterized as having low albedos, having smooth fine-textured surfaces, and consisting in part of homogeneous, Febearing volcanic glass and partially crystallized spheres. Mantling units exhibit low returns on depolarized 3....

Journal: :journal of sciences, islamic republic of iran 2009
m. mortazavi

damavand is a large dormant stratovolcano in the alborz mountains of northern iran located in one of the most populous provinces, which could be adversely affected by tephra fall from damavand. the youngest known eruption is a lava flow on the western flanks with an age of 7.3 ka. the volcanic products are predominantly porphyritic trachyandesite. three major young pumice deposits, named here a...

2001
K. Németh

The pyroclastic rocks of "The Crater", South Island, New Zealand belong to the Miocene, alkaline basaltic Dunedin Volcanic Group and represent an individual eruptive center with possible multiple vents. Three pyroclastic units have been separated at the study area based on textural and compositional features as well as their stratigraphic positions. The central part of The Crater comprises basa...

1980

An exploratory hole UE25a-1) was drilled at Nevada Test Site NTS) to determine the suitability of pyroclastic deposits as storage sites for radioactive waste. Studies have been conducted to investigate the stratigraphy, structure, mineralogy, petrology, and physical properties of the tuff units encountered in the drill hole. This report deals with the interpretation of physical properties for t...

2009
T. M. Gernon

11 The Orapa Diamond Mine (Republic of Botswana) exposes a bi-lobate kimberlite 12 pipe that erupted during the Late-Cretaceous epoch (∼93 Ma) through Archaean 13 basement and volcano-sedimentary rocks of the Karoo Supergroup. Geological map14 ping of the crater zone of the South Pipe has revealed a 15–25 m thick in-situ 15 kimberlite pyroclastic flow deposit. The pyroclastic deposit fills in t...

2014
Timothy A. Goudge James W. Head Laura Kerber David T. Blewett Brett W. Denevi Deborah L. Domingue Jeffrey J. Gillis-Davis Klaus Gwinner Jörn Helbert Gregory M. Holsclaw Noam R. Izenberg Rachel L. Klima William E. McClintock Scott L. Murchie Gregory A. Neumann David E. Smith Robert G. Strom Zhiyong Xiao Maria T. Zuber Sean C. Solomon

We present new observations of pyroclastic deposits on the surface of Mercury from data acquired during the orbital phase of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission. The global analysis of pyroclastic deposits brings the total number of such identified features from 40 to 51. Some 90% of pyroclastic deposits are found within impact craters. The loca...

2007
Károly Németh Shane J. Cronin

A circular argument has been developed and further propagated through a series of studies that link a major climate-modifying eruption in the 15 th century with Kuwae caldera in Vanuatu. Clear evidence in both N and S hemispheres suggests a major eruption with global atmospheric sulphur loading occurred in 1455-56. Concurrent 14 C determinations from pyroclastic units and estimations of caldera...

2007
Lisa R. Gaddis B. Ray

Clementine ultraviolet-visible (UVVIS) data are used to examine the compositions of 18 pyroclastic deposits (15 small, three large) at 13 sites on the Moon. Compositional variations among pyroclastic deposits largely result from differing amounts of new basaltic (or juvenile) matehal and reworked local matehal entrained in their ejecta upon eruption. Characterization of pyroclastic deposit comp...

هاشمی, مهین ,

The study area is part of Karaj Formation in the southern city of Zanjan and is located in the central Iran zone. Rocks of the study area consists of pyroclastic, igneous and sedimentary rocks. Igneous rocks in this aria consist of two categories: acidic (rhyiolite and rhyiodasite) and basic (basaltic andesite).  Sahle section in terms of lithology can be equal of the lower shale and middle tuf...

2014
S. Li R. E. Milliken

Introduction: Pyroclastic deposits on the Moon represent early lunar volcanic processes [1], and models of explosive volcanism indicate that the range of pyroclastic deposits is proportional to volatile content [2]. Therefore, the distribution of lunar pyroclastic deposits and their estimated water content can provide indirect information on the distribution of volatiles in magma source regions...

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