[1] A mechanism for explosive volcanic eruptions based on multicomponent phase equilibria modelling of four explosive volcanic systems is proposed. In each system, either isochoric or isobaric crystallization, where either crystals or crystals and exsolved fluid are chemically fractionated from melt, leads inevitably to near-solidus dynamical instability culminating in violent explosive eruptio...

—The mid-Tertiary-age volcanoes, dikes, and sills of the Navajo volcanic field are classic and geologically-distinctive landforms of the Colorado Plateau. They are the products of structurally-controlled magma ascent, explosive eruptions, and deep post-eruptive exhumation. Igneous rock types include potassic lamprophyres, serpentinized tuffs, and exotic mafic and ultramafic intrusives. These ro...

 Igneous Rocks form from the solidification of molten rock. Intrusive igneous rocks are composed of crystals that are large enough to be seen with the naked eye because these rocks cooled slowly, deep within the Earth thereby allowing time for the crystals to grow. In contrast, extrusive (volcanic) igneous rocks cool very quickly after they erupt from a volcano, and so are composed of microsco...

________________________________________ Introduction __ ___________________________________ Area covered.__________________________________ Aeromagnetic survey.___________________________ Gravity survey.________________________________ Acknowledgments--.. __1________________________ Geology __ __ ____________ _ Rock units_____________________________________ Carboniferous and older rocks._____...

A fast, quantitative image analysis technique was developed to assess potential rock weathering by bacteria. The technique is based on reduction in the surface area of rock particles and counting the relative increase in the number of small particles in ground rock slurries. This was done by recording changes in ground rock samples with an electronic image analyzing process. The slurries were p...

We have performed preliminary mapping of the manganese and iron present in a cross-section of a rock varnish from the Cima volcanic flows in the Mojave Desert, California. Rock varnish is a nanostratigraphic deposit found on typically fine-grained rocks in hyper-arid to semi-arid deserts (Figure 1a) [1]. Rock varnish is defined as consisting of about 70% clay particles held together by about 30...

Volcanic eruptions can emit large amounts of rock fragments and fine particles (ash) into the atmosphere, as well as several gases, including sulphur dioxide (SO2). These ejecta and emissions are a major natural hazard, not only to the local population, but also to the infrastructure in the vicinity of volcanoes and to aviation. Here, we describe a methodology to retrieve quantitative informati...

The Cenozoic volcanic rocks of Ross Island and vicinity, Antarctica, are surface flows, tuffs, breccias, and small intrusives. The prominent rock is basanitoid. Alkali-basalt magma reached the surface over an appreciable length of time and was differentiated to produce a rock series: basanitoid -. trachybasalt -, phonolite. The alkalic, silica-undersaturated rocks are part of a larger petrologi...