Welded tuffs ( and welded lapilli-tuffs ) can be of fallout origin, or deposited from pyroclastic density currents, as in the case of ignimbrites.
12.
:Another model proposed is that the density current became stationary prior to the formation of the rheomorphic structures ( Ragan et al . 1972 ).
13.
Pyroclastic flows that contain a much higher proportion of gas to rock are known as " fully dilute pyroclastic density currents " or pyroclastic surges.
14.
These plumes tend to have higher concentrations of fine ash particles compared to magmatic eruption plumes due to the abrasion within the pyroclastic density current.
15.
As pyroclastic density currents travel away from the volcano, smaller particles are removed from the flow by elutriation and form a less dense zone overlying the main flow.
16.
Pyroclastic density currents, which are referred to as " flows " or " surges " depending on particle concentration and the level turbulence, are sometimes called " glowing avalanches ".
17.
They have found that the average number of days when flows into the lake are high enough to generate these density currents has fallen from 55 a year to 15.
18.
In 1926, Erwin Madelung had developed a hydrodynamic version of Schr�dinger's equation, which is incorrectly considered as a basis for the density current derivation of the de Broglie Bohm theory.
19.
Fronts of some pyroclastic density currents are fully dilute; for example, during the eruption of Mount Pel�e in 1902, a fully dilute current overwhelmed the city of Saint-Pierre and killed nearly 30, 000 people.
20.
In 2005, researchers at the University of Illinois at Urbana-Champaign created a three-dimensional, hydrodynamic simulation of the Chicago River, which suggested that density currents are the cause of an observed bi-directional wintertime flow in the river.
