 Main |
 Vocabulary |
 Prediction |
 Underwater |
 Famous |
|
Main |
Vocabulary |
Prediction |
Underwater |
Famous |
Volcanoes give off many warnings, such as animal and bird movement, melting snowcaps, and crate lakes drying up. However, more efficient and effective detection methods related to the inner workings of an active volcano have been developed. The most common of these instruments are tiltmeters and seismographs.
The tiltmeter was devloped by the Hawaiian Volcano Observatory to measure the ground swell produced by the strain of the magma pushing its way to the surface before an eruption. The mechanism, which has two containers connected by a tube with fluid on each side, is placed in the ground. The fluid then flows from one container to the other as the ground swells. Tilmeters are so sensitive they can detect changes in angle of less than .00006 degree (one microradian). This would be like putting a nickel under a one-mile long board!
The seismometer, developed by Chang Heng, measures and records the vibrations in the earth. It includes a recording device, the seismograph, and produces a graphic record called a seismogram. Modern seismographs record on magnetic tape, instead of scratching traces on smoked paper, which allows for much better analysis. Networks of portable seismographs are used to monitor ground tremors during volcanic eruptions and data can be transmitted now by radio or telephone lines to help warn people.