Volcano Monitoring — Seismic (Educational) скачать в хорошем качестве

Volcano Monitoring — Seismic (Educational)

Earthquake activity beneath a volcano almost always increases before an eruption because magma and volcanic gas must first force their way up through shallow underground fractures and passageways. When magma and volcanic gases or fluids move, they will either cause rocks to break or cracks to vibrate. Volcano Monitoring—Deformation: Tilt & GPS 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 carpenters 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. Animation by Jenda Johnson for IRIS in collaboration with Seth Moran, seismologist, USGS Cascades Volcano Observatory