How can we know that a volcano is getting ready to erupt?
Volcano deformation can provide clues about what is happening deep below the surface. Two techniques used to monitor deformation include Tiltmeters and GPS. Like a carpenter?s level, an electronic tiltmeter uses a small container filled with a conducting fluid and a ?bubble? to measure a change in slope. Tiltmeters measure the amount of tilt in microradians, which is the angle turned by raising one end of a beam one kilometer long the width of a dime (equivalent to 0.00006 degree!). GPS measures the distance between two points to determine if they are moving further apart, as they might if magma was entering the system.
- Moving magma in a volcano can cause the volcano to "inflate"
- Tiltmeters measure subtle changes in the surface of a volcano
- GPS can measure change across the surface of a volcano