The Science of Predicting Volcanic Eruptions
Scorching temperatures, toxic gases, and let’s not forget the s! Monitoring es is an extremely dangerous job, and it comes as no surprise that routinely appears among the top ten deadliest professions in the world! Nevertheless, as seen in video 4.4.1, scientists take risks to monitor volcanoes because it may reduce the chance of a potential eruption taking a populated region by surprise.
Video 4.4.1. Every volcanic eruption is an opportunity to learn about Earth’s interior and to refine our prediction models (1:16).
It is difficult to predict whether or when a volcano will erupt, but scientists closely monitor a volcano over time to look for changes that could show geologic activity. Scientists will measure characteristics such as surrounding the volcano, the deformation of the cone, gas emissions, and past history of volcanic eruptions [1,6]. These measurements will lead scientists to advise officials to take decisive action that can lead to evacuations, and hopefully, the prevention of a catastrophe.
History of Volcanic Activity
How active is a volcano? Scientists compile historical records from cities, towns, and villages surrounding a volcano to learn when, over the course of written history, it last erupted. Geologists can also examine the cooled lava fields along the slopes of a volcano, and even date some of the recently deposited ash and rock to determine when it was last ejected from the vent.
Video 4.4.2. What can scientists see in a particle of ash? Geologists, John Wolff and Michael Rowe, discuss the use of geochemistry to aid in the prediction of volcanic eruptions. Their work centers on geologic activity in the Cascade Range, where a powerful subduction zone off the coast of North America produces constant volcanic activity in the area (3:44). Source: Washington State University, CC BY.
One way to classify volcanoes is by their activity: erupting, dormant, active, and extinct. An erupting volcano, as the name suggests, is currently erupting. A volcano that is not erupting, but remains connected to a magma chamber that might erupt, is called . If a volcano has erupted just once in the past 10,000 years, scientists consider it to be , even if it is in a period of dormancy or currently erupting. The only “safe” volcano is an volcano, which means that we do not expect it to erupt in the foreseeable future. Nonetheless, even extinct volcanoes may surprise scientists and they are still prone to events.
Scientists usually focus their monitoring efforts on active volcanoes, especially those that might affect populated areas. By documenting the eruption history of active volcanoes, scientists could construct a broad timeframe in which it is reasonable to expect an eruption.
When moves beneath an , it can shake the ground nearby. The sudden shaking releases energy in the form of , that is, it produces seismic movements or earthquakes.
A good indicator of a volcano that is just about to erupt is a series or “swarm” of earthquakes. Scientists measure these with instruments called s, which capture the seismic waves released by the movement of the volcanic slope .
In addition to producing earthquakes, the movement of under a volcano can also bulge the flanks of the mountainside. The deformation of the ground along the volcanic slope might not very apparent to the naked eye. Scientists use instruments called s, which precisely measure the angle of a volcano’s slope. When that slope starts to deform, due to pressure from the underlying melted rock and gas, it will change the slope angle of the volcano . The tiltmeter is a sensitive instrument that can detect infinitesimal changes. The deformation process could even cause events.
Some scientists now use the modern technique of to detect subtle changes in the volcano’s shape and slope. Scientists use modern drones and satellites to track slight changes in elevation and temperature in areas that are inaccessible to scientists. Some of these technologies include Light Detection and Ranging (LiDAR), Global Positioning System stations (GPS), and Interferometric Synthetic Aperture Radar (InSAR). Figure 4.4.4 shows the working principle for inSAR.
Some active volcanoes release gases before magma. These gases include sulfur dioxide (SO2), carbon dioxide (CO2), water vapor (H2O), and hydrochloric acid (HCl). Scientists will detect these gases near the vent of the volcano or sample them and later analyze the gas concentration with sophisticated instruments, called spectrometers. The increase in the concentration of certain gases may indicate an imminent eruption .
A hazardous molten rock ejected by volcanic eruptions that is at least more than 2.5 inches in diameter.
an area on the Earth's surface where lava, ash, and/or volatile gases erupt and eventually solidify into rock.
The study and monitoring of volcanoes.
Vibrations and energetic waves produced by the movement within Earth's crust and interior.
A volcano that is not currently erupting but still has the possibility of becoming active.
A volcano that has erupted at least once over the past 10,000 years and has the possibility of erupting in the future.
A volcano that is not currently erupting and is not expected to erupt in the future.
The process in which rock, soil, or sediment moves down a slope under the force of gravity. Mass wasting is an umbrella term that includes hazards such as landslides, debris flows, rock falls, and mudslides.
molten rock that can be found beneath the Earth's surface.
An instrument that measures and records seismic waves caused by geologic activity in the Earth's interior. The graphical product of a seismograph recording is called a seismogram.
An instrument that detects very small changes in movement in the angle of the ground over time.
The technique of mapping, scanning and monitoring physical planetary characteristics using emitted and reflected radiation. This is done using drones, satellites, vessels, or aircraft from a distance.