Science of Volcanic Activity Prediction
Since the dawn of history, volcanoes have been an awe inspiring feature of the earth that has frightened and intrigued mankind. Volcanoes have taken the lives of over 250,000 people in the last three hundred years and changed the lives of millions of others, but up until recently humans have had very little understanding of the volcanic processes that presage an eruption. The advent and implementation of new technologies and scientific methods has allowed us to begin to comprehend the inner workings of one of nature's most powerful forces. Through understanding how volcanoes work, volcanologists hope to accurately predict when an eruption may occur, what the magnitude and type of eruption will be, and what effect it will have on the surrounding area. Accomplishing this daunting task will ensure that in the future when an eruption occurs, the population at risk will be prepared and lives can be saved.
Numerous methods are available for monitoring volcanic activity, and scientists typically synthesize data and observations from all methods available in order to obtain the most comprehensive look at the area being observed. One frequently used technique is monitoring seismic activity that may indicate flow of magma and gas beneath the surface. As magma at extreme temperatures of sometimes over one thousand
Degrees Celsius rises through cracks in the Earth's crust, the intense temperature and pressure causes the surrounding rock to crack, as illustrated in the diagram above. This brittle fracture of the surrounding rock often causes earthquakes or vibrations called tremors. Usually these earthquakes are of magnitude 2, 3 or lower, and seismographs monitor these quakes so that they can be analyzed. Generally these small earthquakes increase in frequency prior to a volcanic eruption, but this is not always the case.
The graph to the right displays the number of earthquakes in the months leading up to three eruptions that occurred on June 27, August 18, and September 16-17 of 1992 at Mt. Spurr, located 80 miles west of Anchorage, Alaska. The vertical red lines indicate the eruptions. The graph shows that there was an erratic but visible increase in the frequency of seismic activity leading up to the first eruption. It also shows that the second and third eruptions were not preceded by a marked increase in seismic activity, and that during two weeks following the last eruption in November and December, a large frequency of earthquakes took place without an eruption occurring afterwards. This illustrates how difficult it can be to predict when an eruption is likely to take place and underscores the importance of using several methods concurrently to predict volcanism.
Monitoring ground deformation in the vicinity of a volcano is another valuable tool for understanding what's going on underground. When magma rises, it often causes the rock above it to deform or uplift in the form of a...