Which monitoring method observes magma movement by detecting changes in volcano shape?

• A. Seismographs
• B. Ground-swelling detection by satellites
• C. Hazard maps
• D. Emergency service training

Answer: (B)

When magma moves toward or beneath a volcano, the ground often inflates and bulges as pressure builds. Detecting that deformation is a direct way to monitor magma movement. Ground-swelling detection by satellites uses remote sensing techniques (like InSAR) to measure tiny changes in the volcano’s surface over time. By comparing radar images taken at different times, scientists can map where the ground has risen or subsided, revealing where magma is accumulating or moving.

Seismographs, while crucial for sensing earthquakes and eruptive signals, don’t directly show changes in the volcano’s shape. Hazard maps summarize risk and potential impacts, not real-time deformation. Emergency service training focuses on response procedures, not detecting magma movement. So satellite-based ground swelling is the best method for observing magma movement through changes in volcano shape.