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VolcanosVolcanos occur all over the world.The best know volcano zones occur on the destructive plate margin around the Pacific Ring of Fire.This chain of volcanos that lie along the west coast of central and south America,Japan and the Philippines,across New Zealand and into the Atlantic.Volcanos also occur in mid-ocean along the line of ocean ridges.The Mid-Atlantic Ridge is an example of ocean floor volcanos.When these volcanos erupt lava flows from the cracks building up the ocean floor.Volcanos can also occur away from plate boundaries.These are the Hawaiian Volcanos.As you can see there are lots of places were volcanos occur.Sometimes these volcanos are where humans have settled.To help protect our belongings and save human lives we have developed ways to predict when volcanos are about to erupt.Here are some.

Predictions Two main methods are used to predict when volcanos are about to erupt.

These methods are called geophysical techniques,and chemical techniques.

The geophysical method can detect any changes in the rock below. As the magma rises it forces the rocks apart,Which can create minor earthquakes on and or around the mountain. These can be detected on a seismographs. A seismograph picks up the seismic waves the earthquake gives off and records them. A seismograph works by a pen and a weight suspended on a spring. As the earth shakes the pen writes the waves,called a seismogram,on a revolving drum. A comparison can be used. They take two or more seismographs readings to pin point exactly where the magma is trying to surface. This technique is successful in Hawaii where they are a lot of volcanos. The place and the time of eruptions have been forecast accurately. Before a volcano is about to explode the ground around it swells with...