mall Juan de Fuca plate colliding with the bigger plate that carries North America. When one plate collides with another plate, one slides under the other into the Earth's mantle causing rock to melt, magma to rise and volcanoes to erupt. This is what happens all around the rim of the Pacific Ocean. Can Volcano eruptions be predicted? Earthquakes are the biggest clue that a volcano that has been dormant is coming back to life. Tremors under the volcano and in nearby areas are sometimes caused by magma rising and moving rock around. The scientists who study volcanoes, volcanologists, can not predict when the eruption will happen, but they can measure the gases seeping from the volcanoes and the changes in the temperature of the earth. These are clues that let them know that activity is increasing. They use an instrument called a tiltmeter. For weeks before MSH erupted, volcanologists were able to warn the people in the area that the rock around the volcano was active. The volcanologists measured the bulge of the volcano and the changes in the surface of the mountain. This helped to save many lives since they were able to let people evacuate the area. Current plate movement can be tracked directly by using ground-based or space-based geodetic measurements. Geodesy is the science of the size and shape of the earth. Ground-based measurements are taken with very precise surveying techniques using laser electronic instruments. Because plate motions are global in scale, they are measured by satellite based methods. Among the techniques are VLBL (very long baseline interferometry) SLR (satellite laser ranging, and GPS (Global Positioning Systems) and are all based on technology developed for the military, aerospace, radio astronomy and satellite tracking. By monitoring the interaction of the Pacific Plate and the surrounding continental plates, scientists hope to learn more about the events leading up to earthquakes and volcanic eruptions in th...
