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Long Valley Caldera: Risk of Eruptions and Earthquakes
Like all supervolcanoes, though minimal, there is a risk while visiting. Small eruptions along Mono Lake have occurred as recently as the 1800s. Many earthquakes have occurred even more recently. Earthquakes are caused by slowly moving faults and sometimes even pressure build up of magma. Starting in 1978, frequent earthquakes have been prevalent. In 1980, a string of four 6.0, or higher, magnitude earthquakes struck the Long Valley area. Since then, scientists have been heavily monitoring the situation. In the early 2000s, the caldera was reported to have risen approximately two and a half feet since the 1980 earthquake. The forming dome is from rising magma. It is also noted that trees around the Mammoth Mountain area have been dying since around 1990 due to excess CO2 seeping through the soil from the magma below.
While all these recent findings do not necessarily point to an imminent eruption, scientists have increased their monitoring of the Long Valley Caldera. The U.S. Geological Survey, or USGS, established a color system where a group of four different colors describe the activity level of a volcano. These colors also help the USGS decide what actions to take. Code Green tells the general public that there is no immediate risk to visit the caldera. The only actions taken by the USGS are routine check ups and monitoring. Code Yellow tells the public to proceed with caution. This is the “watch” color. The USGS begins to intensely monitor all aspects of the caldera. Code Orange is the “warning” color. An eruption is likely imminent. Code Red alerts everyone that an eruption is underway. The USGS keeps civil authorities up-to-date at all times. During a Code Red, the USGS will continue to monitor not only the progress of the eruption, but if or when it is likely to intensify.
Volcano eruptions are not the only thing being monitored. The USGS is just as extensively monitoring possible earthquakes, as well. Earthquakes are not random. They are caused from the movement of magma underground. Because of this, scientists are able to track and somewhat predict when an earthquake could happen. The most accurate way to predict an earthquake is with a seismometer. There are 61 seismometers around the Long Valley Caldera to ensure complete safety.