23 blasts reveal Mount St. Helens’ hidden magma

In 2014, scientists conducted an unprecedented seismic experiment at Mount St. Helens to better understand the volcano's hidden internal structure. Known as the Imaging Magma Under St. Helens (iMUSH) project, the researchers deliberately detonated 23 controlled explosions around the mountain. They then utilized a vast array of seismic instruments to record the resulting seismic waves traveling through the Earth.

The experiment's goal was to create an underground map of Mount St. Helens, revealing more than just a simple magma chamber. Instead, the data showed a complex magmatic plumbing system. One of the key findings was the presence of an upper-crustal low-velocity zone, located roughly 4 to 15 kilometers beneath the volcano. This region, characterized by slower seismic wave speeds, suggests that magma may be stored in a mixture of molten material, crystals, and solid rock within this zone.

The iMUSH findings also revealed that Mount St. Helens' underground plumbing is far more intricate than previously thought. The volcano appears to have multiple layers of varying seismic properties, including unusual high-velocity regions deeper underground. These variations could be attributed to accumulated crystallized magma, known as magmatic cumulates, or other geological processes.

Mount St. Helens is closely monitored due to its history of devastating eruptions, most notably the 1980 event. This 2014 seismic experiment offered a unique opportunity to peer into the volcano's interior, providing a detailed look at its internal structure. While the research confirms the existence of a major magma-storage zone, it also highlights the complexity of Mount St. Helens' underground plumbing, suggesting that there is still much to learn about the volcano's behavior.