A volcano is the point at which molten rock, which comes from deep within the earth, reaches the earth's surface. In some cases, volcanoes can simply be holes in the ground (vents), but generally they form conical mounds - built up progressively on a basement of pre-existing rock, and is composed of an accumulation of lavas and volcanic ejecta.
Molten rock reaches the surface by a central pipe, and by dikes, that bring this magma to the surface from a magma chamber situated anywhere from 1,000 feet to 2 miles beneath the vent.
The magma chamber for a particular volcano is generally very complex in shape, and is itself fed by magma from a deeper source, up to even 200 miles below the earth's surface.
The shape of the volcano above groundvaries depending on the chemical composition of the magma in question, as well as its temperature, as well as the amount of dissolved gas within it. All these factors combine to determine the frequency and violence of the eruptions, and thus what kind of cone, if any, is created.
_________________
Bibliography
Living Mountains, How and Why They Erupt, by Jacques Kornprobst and Christine Laverne
No comments:
Post a Comment