Earthquakes are caused by the movement of 50-mile-thick plates that comprise the earth's crust. More than two thousand earthquakes occur daily somewhere on our planet, but about 95 percent of them are too weak to be felt \_11\_ sensitive seismometers. \_12\_ are felt by humans, most cause relatively little damage, particularly if they occur in sparely \_13\_ areas. Scientists have observed that certain phenomena seem to occur before an earthquake as the pressure within the plates intensifies. Myriads of tiny cracks appear in the rock, causing it to expand and uplift the ground above it. The pressure squeezes water out of the rock, thereby \_14\_ nearby water levels. Also the rock becomes more resistant to electric current, and radon gas is released. Scientists hope that these \_15\_ phenomena will provide keys to predict when and where an earthquake will occur, thereby enabling them to warn people to evacuate the area. While the earthquake itself cannot be prevented, at least lives may be saved. There are basically two types of stress placed on human beings. One type involves physical activity and its demands; the other type is the result of mental and emotional demands. Whether physical or emotional in origin, stress causes the body to react in similar ways. In the first stage, your body prepares to meet the stress. The heartbeat and respiration rates increase, and the pupils of the eyes dilate; the blood sugar level increases, and the perspiration rate speeds up, while digestion slows down as blood and muscular activity is diverted elsewhere. In the second stage, your body returns to normal and repairs any damage caused by the stressful situation. However, if stress continues, the body cannot repair itself, and the final stage, exhaustion, then begins. If this stage continues, physical and emotional damage will occur. These stages of stress reaction are generally the same, whether the stress is caused by a cross-country run, a first date, buying a house, or narrowly missing an automobile accident.