Introduction
Volcanology and seismology have a strong interplay with each other, as they are two geological processes that often go hand in hand. Seismology, the study of earthquakes, is a science that examines dynamic Earth's inner structure and the spread of seismic waves through it. Volcanology on the other hand, looks at the magmatic and sedimentary materials found within volcanoes and their surrounding areas, as well as the rocks that are associated with them.
Although it seems like the two sciences should be completely separate, there is a lot of crossover between the two. Volcanic eruptions and earthquakes can take place at the same time, making it impossible to observe one without the other. In this article, we will be looking at the different ways seismology and volcanology interact, and the advances that have recently been made in this field.
Seismology
Seismology is the study of earthquakes and earth tremors, which are caused by the movement of lithospheric plates or within the Earth's mantle. It is a science which allows us to gain insight into the structure and composition of our planet and the way in which it responds to stresses. In this way, seismology can be used to study and predict volcanic eruptions.
Seismicity is the term used to describe the level and frequency of seismic activity in an area. It can range from mild tremors caused by natural movement of rocks and sediment, to intense and dangerous earthquakes. Seismometers, which measure earthquake vibrations, allow seismologists to detect these tremors and plot the epicenter and magnitude of the seismic activity. Earthquakes caused by volcanic activity often have a different signature than those formed due to tectonic plate movement, helping seismologists to distinguish between the two.
Advances in Seismology
Recent advances in seismology have made it possible to observe and monitor volcanic activity more effectively. Seismic tomography is a technique that has had a great impact on volcanology by combining seismic data with other types of data, such as gravity data, to create three-dimensional images of the Earth's subsurface. This allows scientists to detect changes in the Earth’s structure, such as magma chambers forming or propagating fractures, which can all be potential precursors to volcanic eruptions.
Modern seismometers are also much more sensitive than their predecessors, and can pick up the slightest seismic disturbances which may warn of impending explosions. Seismologists can also use techniques such as seismo-acoustic coupling to study the Earth's crust for signs of fractures and fracturing, which can be a warning sign of an impending eruption.
Volcanology
Volcanology, also known as volcanic geology, is the study of the different phases of a volcano, from the first signs of activity to the aftermath of an eruption. Volcanologists analyze volcanic rocks, magma, and gases, to understand a volcano’s mechanics and its potential impacts on the surrounding environment. They also measure and monitor changes in the Earth’s structure, such as ground deformation, which can indicate underground magma movements.
Volcanic ash is also analyzed to determine the composition of the erupting magma, which can provide insight into when the next eruption might happen. Volcanologists also use geophysical survey techniques, such as seismic refraction and gravimetric surveys, to view and map the magma chamber beneath a volcano so they can observe and monitor the magma movements more closely.
Recent Advances in Volcanology
Recent advancements in volcanology have enabled scientists to monitor a higher number of volcanoes for longer periods of time. Global seismic networks can be used to detect the expansion of magma chambers and the changes in ground deformation, as well as more subtle cues that may indicate volcanic unrest. Laser-induced flourescence is a method that can be used to measure the ambient temperature at a volcano, providing data to assess potential risks associated with eruptions.
Remote sensing also gives volcanologists the ability to view active volcanoes from above. The use of drones and satellites can provide real-time images of volcanic eruptions and can provide data such as their chemical make-up, as well as the distribution of ashfall.
Interactions Between Seismology and Volcanology
Volcanic eruptions and earthquakes often take place at the same time, creating a strong interplay between the two sciences which was highlighted by the eruption of Mt. St. Helens in 1980. As the mountain's slopes softened in the impending eruption, the Earth's crust in the surrounding area shifted, causing a series of large earthquakes. These seismic patterns were indicative of what was about to occur and gave seismologists a better understanding of imminent volcanic eruptions.
In 1995, the eruption of Rinjani on the Indonesia island of Lombok was similarly monitored through seismology. The volcano had been showing signs of unrest for a number of weeks and seismologists predicted an eruption by observing the increase in seismicity from the magma chamber below it.
Conclusion
Seismology and volcanology are two related geological processes which depend on each other to provide a complete picture of what is happening on and inside the Earth. Seismologists can use their data to study and predict volcanic eruptions, while volcanologists analyze ashfall and geophysical surveys to determine the composition of a volcano’s magma chamber and help seismologists understand seismic patterns surrounding the eruption. Recent advances in both sciences have enabled scientists to monitor and study volcanoes more effectively, and to predict eruptions more accurately.