Viscous Fluid Volcano Vibration Mechanisms

Volcanoes are very complex parts of nature. This is quite unfortunate as being able to predict their evolution and eventual eruption accurately would be a very useful ability to have. One of the unique things about modelling volcanoes is the movement of magma which clearly can’t be assumed to follow the same flow mechanics as water. For a start magma  is very viscous being molten rock and is also always close to becoming solid again. Also the presence of magma has a tangible effect on its surroundings due to the heat and so it can effect its own flow path in a way water can’t. But one of the hardest things to understand is how magma reacts when it is in fact staying completely still.

The pressures present under a volcano mean that rather then the liquid moving instead cracks and fissures are more likely to move into the magma chamber’s vicinity. This process is a challenging one to model and it is only roughly theorised that this interaction could produce mechanical vibrations through the local rock. The frequency of these phonons can give details about the current state of the volcano and so these events get divided into high and low frequency with the occasional hybrid event which produces high frequency to begin with but degenerates a low frequency hum over time. Because basalt is known for having many minuscule cracks a block of basalt was taken from the lava flows of mount Etna in Italy. The samples were experimented under both saturated and dry conditions to see how these effected the hybrid vibration process. It was found that after the system is made initially unstable by the interaction of the crack and the magma a second phase of instability occurs when the high frequency phonons ebb away the pressure on the liquid cavities increases. This can cause secondary cracking and may help magnify the low frequency vibrations. Observational data gathered from hybrid frequency volcanoes also seems to assent to this theory. The other major part of this study was the development of the theoretical modelling technique known as K-chains. These K-chains are a form of nodal analysis over time to help see how the vibration networks develop in the mathematical form of 3D vectors. These chains will hopefully be developed into the analysis of vibrations over large temperature gradients that are so often found in volcanic rock.


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