Question

Assume that you want to monitor a volcano that has erupted several times in the recent past but appears to be quiet now. How might you determine if magma were actually moving through the crust beneath the volcano? Suggest at least two phenomena you would observe or measure.

Short answer

Observe earthquake patterns and ground deformation to monitor magma movement.

Step-by-step solution

Analyze Seismic Activity

Begin by monitoring seismic activity around the volcano. When magma moves through the Earth's crust, it causes small earthquakes, known as volcanic tremors. By using seismographs, you can detect and measure the frequency and magnitude of these tremors. An increase in seismic activity can suggest movement of magma beneath the volcano.

Measure Ground Deformation

Install GPS stations and tiltmeters around the volcano to measure ground deformation. As magma rises and accumulates, it can cause the ground to inflate or deform, which usually involves subtle changes in the ground's elevation and slope. Analyzing this deformation can help indicate if magma is moving beneath the surface.

Key concepts

Seismic Activity

Seismic Activity is a key indicator of volcanic activity because it reflects the movement of magma beneath the surface. When magma forces its way through cracks in the Earth's crust, it generates seismic waves, which are detected as tremors.
Seismologists deploy seismographs around volcanoes to record these tremors.

• Seismographs measure the frequency and magnitude of the small earthquakes.
• A sudden increase in the number of tremors often signals that magma is on the move.

By analyzing seismic data, scientists can learn about the magma's path, how quickly it's moving, and even its volume.
This information is crucial for predicting future eruptions and ensuring timely warnings for nearby populations.

Ground Deformation

Ground Deformation occurs when magma moves and accumulates beneath a volcanic area, causing the Earth's surface to rise or change shape.
This deformation can be subtle and typically requires sensitive instruments to detect.

• GPS stations are used to track changes in the precise location of points around the volcano.
• Tiltmeters are used to measure changes in the slope of the ground.

Through careful monitoring of ground deformation, scientists can detect patterns that suggest magma is gathering under the surface.
Since increased ground deformation often precedes eruptions, it allows for early warnings and hazard mitigation plans to be put into place.

Volcanic Tremors

Volcanic Tremors are continuous, rhythmic seismic signals that occur as magma moves through volcanic conduits. Unlike typical earthquakes, which are brief, volcanic tremors can last from minutes to hours.
These tremors provide important clues about volcanic activity.

• Amplitude of tremors can indicate the vigor of the rising magma.
• Continued presence of tremors can alert scientists about an impending eruption.

By studying the characteristics of these tremors, volcanologists can gain insights into the internal processes of the volcano.
This understanding helps in designing better monitoring and response strategies to mitigate risks associated with volcanic eruptions.