Module 1, Investigation 3: Predicting Eruptions Introduction Welcome! Volcanoes are either "active" or "extinct". Active means that the volcano has erupted during the past 10,000 years. It can also mean that the volcano is expected to erupt within the next 10,000 years. A "dormant" volcano is an active volcano that is not erupting right now. More and more people live in volcanic areas. This puts more people and property at risk. The USGS predicts that future eruptions could affect hundreds of thousands of people. That is why scientists monitor active volcanoes. They want to warn communities before a volcano erupts. In this investigation, you will learn how scientists carry out this important work. But be forewarned. Predicting eruptions is not an exact science! Each volcano is unique. There are a lot of things happening underground that we cannot see. Scientists have many different ways to try to see if the system is becoming unstable. Think about what you have learned about what happens during volcanic eruptions. What physical changes do you think might tell us that an eruption is going to happen soon? How could these be monitored? Record your ideas in your field notebook. CE3 Placemarks- Module 1 Investigation 3 Page 1
Folder 1: Seismic Activity (Mount Rainier, Washington) Seismographs People often feel small earthquakes or tremors just before a volcano erupts. These movements are called seismic activity. What causes this? Can we use it to help predict eruptions? You have learned that before a volcano erupts, pressure builds up in the magma chamber. Magma is forced through cracks in the surrounding rock. As this happens, the pressure of the gas and liquid in the volcano's underground plumbing system can fluctuate sharply. These abrupt changes in pressure are transmitted through the surrounding rock, causing tremors. The rock may even break or shift as magma is injected into it. This creates small earthquakes. These events have characteristic "signatures". This means that they make the ground shake in distinctive ways. Seismographs are very sensitive instruments. They are used to record these movements. Scientists compare these signals with those of other types of events. In essence, scientists learn to "speak the volcano s language"! Volcanologists set up many seismograph stations to track seismic activity. The seismic signal of an earthquake changes as it travels through the ground. Scientists try to record the same earthquake at several stations. This allows them to pinpoint where the earthquake started. CE3 Placemarks- Module 1 Investigation 3 Page 2
Folder 2: Ground Deformation (Mount St. Helens, Washington) Tiltometers and EDM Think about the animations you saw in Investigation 1. The surface of the volcano bulged as magma was pushed up. This is called ground deformation. Scientists can measure it using electronic tiltometers. These instruments act much like a carpenter s level. They measure tiny changes in the slope or "tilt" of the ground. Scientists also use electronic distance meters (EDM) to measure ground deformation. To do this, they first place a target on the volcano surface. They then use the EDM to measure how far the target moves each day. By plotting these results, they can calculate the rate at which the ground is deforming. A change in rate could mean a change in underground activity. Both tiltometers and EDM techniques require scientists to work up on the volcano itself, for as long as they dare! CE3 Placemarks- Module 1 Investigation 3 Page 3
Folder 3: Hot Spots (Chiliques, Chile) Infrared Imagery Thousands of satellites orbit Earth each day. Each has a specific purpose. Some transmit television or cell phone signals. Some are for geographic positioning (GPS). Others collect data about Earth and its atmosphere. This type of monitoring is called remote sensing. Some satellites collect digital images of Earth. Some have instruments that detect visible light (light we can see). Others detect infrared radiation. This has longer wavelengths than visible light. It shows the temperature at Earth's surface. CE3 Placemarks- Module 1 Investigation 3 Page 4
Folder 4: Volcanic Gases (Mount Pinatubo, Philippines) Gas Sampling Have you ever wondered why when you open a bottle of soda pop, bubbles suddenly appear and rise to the surface? Could the same thing happen in a volcano? Most active volcanoes give off gas and water vapor. The gases can come out of the crater, nearby hot springs, or small openings called fumaroles. Some people think that increasing pressure below ground forces the gases out. But actually the opposite is true. It is decreasing pressure underground that allows the gases to escape. When magma is deep underground, it is under great pressure. This pressure causes gases to stay dissolved in the magma. Magma is forced into the surrounding rock and the magma chamber expands. This causes the pressure in the volcano s internal plumbing system to drop. The drop in pressure lets gases escape the magma. The gases are less dense than the magma, so they rise to the surface. This is why changes in escaping volcanic gases can help us predict eruptions. They tell us that the magma is expanding. This technique was used to help predict the eruption of Mount Pinatubo in 1991. CE3 Placemarks- Module 1 Investigation 3 Page 5
The most common volcanic gases are water vapor (H 2 O), carbon dioxide (CO 2 ), and sulfur dioxide (SO 2 ). Sampling can be done by a scientist or by a sensor that sends data back to the scientist. It can also be done by a sensor mounted on an aircraft. All of these techniques are time consuming, expensive, and in some cases, dangerous. Folder 5: Summary (Active Volcanoes) Where on Earth? Now you have learned about how scientists monitor volcanoes to predict eruptions. But where should this work be done? Have you ever thought about how many active volcanoes there are on Earth today? Watch the video below to find out. [Active Volcanoes Video] Folder 6: Going Further (USGS Hazards Program) Current Activity Alerts You can visit the USGS Volcanic Hazards website to view the latest US volcano alerts and check to see if there are any active volcanoes near your home. CE3 Placemarks- Module 1 Investigation 3 Page 6
Folder 6: Going Further (Gas Plume Tracking) Gas Plumes You have seen how volcanic gases from Laki affected people far away from the volcano. When a volcano erupts, scientists want to see what areas will be affected. To do this they track the plumes of volcanic ash and gas from space. The Soufrière Hills Volcano erupted on May 20, 2006. A large cloud of ash and gas was ejected into the stratosphere. NASA s Aqua satellite collected infrared data to track the plume. The plume took three days to cross the Caribbean Sea and reach Central America. CE3 Placemarks- Module 1 Investigation 3 Page 7