Eruption column
An eruption column is the fountain or cloud made up of lava or lava fragments , igneous gases , entrained rock and mixed in air , which occurs during many volcanic eruptions . The spectrum ranges from a few hundred meters high lava fountain to clouds of ash that reach far into the stratosphere .
Emergence
An eruption column can be divided into two areas. First of all, due to the high pressure in the magma chamber, the magma gas mixture is ejected from the chimney at supersonic speed . This lower area is called the gas thrust region . An essential mechanism is the formation, growth and bursting of gas bubbles in the upper part of the magma chamber and in the chimney. The resulting acceleration is only enough to throw the magma up to several hundred meters.
In the case of higher eruption columns, the ambient air is sucked in turbulently into the glowing gas thrust region. As a result of the heating, the gas volume increases suddenly. The resulting mixture is lighter than the ambient air and rises as a convective eruption column , with the rock material contained being torn up with it.
It now depends on the gas content, the initial acceleration in the chimney, the fragmentation in the gas thrust region and the amount of magma per unit of time whether it remains in a lava fountain or whether a convective eruption column arises and what height it reaches. In extreme cases, it only reaches layers of air of the same density in the stratosphere. In this zone it will rise a little further due to its speed, but then sink and spread sideways in the direction of the wind.
If certain parameters change in the course of the eruption, in particular the gas content, the muzzle velocity, the vent radius and the mass eruption rate, the column can collapse. The complete or partial collapse of eruption columns is one of several possible causes of pyroclastic density currents and thus a source of volcanic hazards.
See also
Web links
- San Diego State University: Eruption model (English)
Individual evidence
- ↑ a b c Hans-Ulrich Schmincke: Vulkanismus . Primus Verlag, Darmstadt 2010, ISBN 978-3-89678-690-6 .