9.9

 Our understanding of volcanic collapse is improving all the time, but they are still difficult to predict.

Because each volcano in unique, every volcanic collapse is unique. This makes them difficult to predict. They can occur with or without warning, and they can occur because of one or many factor. However, research is constantly improving our understanding of this phenomena. Although there is much more to learn, we have come a long way.

Current research in the field of understanding volcanic collapses, landslides, and debris flows is being done by numerous people and includes the following studies:

1) Field studies- discovering new collapses and causes of past collapse. Now that scientists are aware of what to look for in the field, each volcano can be assessed and new clues could be found as to why they collapse.

Photographs of typical avalanche-induced lahar, showing A) alternation of altered pyroclastic and brecciated layers with solid lava flows; B) massive, unsorted large blocks in a clay matrix (modified from Carrasco-Núñez et al., 2006).

2) Fluid Dynamics- studying fluids in motion to better understand debris avalanches, landslides, and lahars. Physics and mathematics can be used to understand how particles move down a slope. Computer simulations can also be used to understand how landslides travel or to predict future scenarios.

A computer model is used to simulate the debris flow from Mount St. Helens (Ward, S. and Day, S., 2006 )

Examples of lahars generated using a modeling program showing the flow path and speed. (left) 1963 Little Tahoma Peak debris avalanche (Mount Rainier, Washington) /modified from Sheridan et al., 2005. b) El Zaguan debris avalanche, Nevado de Toluca volcano, Mexico (modified from Capra et al., 2008)

3) Numerical Modeling– Describing rocks numerically through field and laboratory analyses which can then be inputted into computer modeling programs to look at how the volcano is deforming or how the slope will fail.

Numerical modeling of Etna Volcano shows where the volcano is moving the most (courtesy of Tibaldi, A.)

4) Analog Modeling– By definition, analog modeling is the process of representing information of a particular subject by another particular subject, often on a smaller scale. In the case of volcanic stability, this means building a smaller model of the volcano out of materials such as sand. By placing the model on a moving table, natural situations can be modeled such as movement along faults or seismic shaking. Additionally, internal magma pressure can be modeled by using a balloon filled with liquid that expands. This will deform the layers and can result in collapse. An example of this type of experiment and the interpretation is shown below:

Analog modeling results in flank collapse as the table underneath the mound moves to simulate plate movement (Tibaldi, A., Rust, D., Corazzato, C., and Merri, A., 2010.)

5) Interferometry-superimposing electromagnetic waves to extract information about how the volcano is changing. This method can show scientists how the volcano’s edifice is changing– for example if magma is rising or a flank is moving slowly downwards. It is described in more detail here.

Interferometry output which shows different intensities of deformation at a caldera in Oregon (C. Wicks, USGS)

6) Geodetic Studies– measurement and description of changes in the edifice. This can be done using GPS (Global Positioning System), tiltmeters, or EDM (electronic distance meters). Like interferometry, understanding how the volcano is changing can give scientists insight into the potential of volcanic landslides.

Geologist using GPS to measure the changes in the volcano's edifice (USGS)

 

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