pumiceous การใช้

• Phonolites are vesicular and pumiceous in nature, although phonolites with trachytic texture are also present.
• Block flows, lava flows, lava domes and some ignimbrites of pumiceous composition form this composite volcano.
• In the Eifel region of Germany a trachytic, pumiceous tuff called trass has been extensively worked as a hydraulic mortar.
• An eruption of Laguna Xilo?6100 years ago produced pumiceous pyroclastic flows that overlay similar deposits of similar age from Masaya.
• The lower member consists mainly of unwelded ( unjoined ), but heavily compacted, pumiceous lapilli-tuff and crystal tuff strata.
• The elongation of the microvesicles occurs due to ductile elongation in the volcanic conduit or, in the case of pumiceous lavas, during flow.
• The Seelys formation, next in the order, consists of lithic tuff and pumice-littered lithic lapilli-tuffs, banded, pumiceous, crystal tuff, and densely welded crystal tuff.
• Vitric ash particles from high-viscosity magma eruptions are typically angular, vesicular pumiceous fragments or thin vesicle-wall fragments while lithic fragments in volcanic ash are typically equant, or angular to subrounded.
• Glassy forms of trachyte ( obsidian ) occur, as in Iceland, and pumiceous varieties are known ( in Tenerife and elsewhere ), but these rocks as contrasted with the rhyolites have a remarkably strong tendency to crystallize, and are rarely to any considerable extent vitreous.
• These were lined with crumbling, rust-colored, oxidized ore, beneath which there was often unaltered galena . "'Sometimes "'these caves are lined and partly filled with "'a light, porous, pumiceous sponge of quartz " '.
• The whole edifice and the adjacent Miocene El Plateado volcano, as well as the western flank of neighbouring Ojos del Salado volcano, are covered with a thick layer of pumiceous ash fall, probably produced by the collapse of an eruption column . ) north and Puntiagudo south is largely buried beneath the massif.