We present results from a numerical conduit model of nonequilibrium magma degassing. We show that CO2 /H2O concentration ratios in pyroclastic obsidian from the ca. 1340 A.D. Mono Craters eruption may record nonequilibrium degassing during magma ascent. Our results also indicate that permeability-controlled, open-system gas loss is consistent with obsidian formation and promotes nonequilibrium ...

Obsidian is a natural volcanic glass formed after eruptions if very rapid cooling of lava occurs. In particular conditions, the silicate ions cannot reach crystalline lattice ordered formation and assume chaotic arrangement, giving origin to obsidian flows. has been used since Paleolithic period make tools because its durability; in Neolithic period, trade played an important role Mediterranean...

The paper aims at merging the first results from analyses of georesources exploited in site Piano dei Cardoni (Ustica island, Italy) during Neolithic phases its occupation (Middle-Late Neolithic, 4.7-4.2 ka cal BC). Grinding tools consist a very varied typology local volcanic rocks, easy to collect and available close investigated site. A selection shapes lithology is applied reach best perform...

Michael S. Ramsey (Y) 7 Jonathan H. Fink Department of Geology, Arizona State University, Box 871404, Tempe, Arizona 85287–1404, USA Fax: c602 965 1787 e-mail: ramsey6elwood.la.asu.edu Abstract Remote monitoring of active lava domes provides insights into the duration of continued lava extrusion and detection of potentially associated explosive activity. On inactive flows, variations in surface...

This article presents archaeological data on Late Postclassic long-distance trade in central and northern Mesoamerica. A ~ t e c trade goods from the Basin of Mexico (ceramics and obsidian) are widespread, while imports from other areas are much less common, both in the Basin of Mexico and elsewhere. The artifactual data signal a high volume of exchange in the Late Postclassic, and while trade ...