Not all eruptions are the same. Sometimes, there is a huge explosion. The hot magma shoots

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1 Natural Disasters

2 A natural disaster is an event that happens in nature. It is an event that can cause a lot of damage. Volcanoes, earthquakes, and tsunamis are all natural disasters. Volcanoes A volcano is a special kind of mountain. It has an opening that allows hot, liquid rock, called magma, to escape from inside the Earth. There are about 1,500 active volcanoes in the world. An active volcano is one that recently erupted or is likely to erupt in the future. Most volcanoes around the world are in an area called the Ring of Fire. It makes a horseshoe in the Pacific Ocean. The Ring of Fire includes the west coast of North America. That is why most volcanoes in the United States are in Alaska, California, Oregon, and Washington. Hawaii is in the Pacific Ocean. It is also in the Ring of Fire. You may wonder why so many volcanoes are in the Ring of Fire. The answer lies beneath the Earth s surface.

3 The Earth s crust is made up of huge pieces of rock. They are called plates. These plates fit together like a puzzle, but they are always moving. They bump into each other. They pull away from each other. Under the plates is the hot mantle of the Earth. Magma from the mantle forces its way up through the plates. Pressure from the magma and gasses builds until the volcano erupts. With each eruption, the volcano grows taller and wider with new layers of rock and ash. up through the volcano. It rises high in the air. Once magma reaches the surface of Earth, it is called lava. Ash, containing pieces of rock, also spews up into the air. Ash clouds can extend for miles. They can harm people s lungs as they breathe in the air. Other eruptions are calm. Lava flows gently from the volcano s opening. Not all eruptions are the same. Sometimes, there is a huge explosion. The hot magma shoots

4 People who live close to a volcano want to get away from an eruption, but volcanoes are hard to predict. Scientists study the volcano s history. They look for signs that can serve as a warning the volcano will soon erupt. Scientists look for rising temperatures. They look for swelling of the volcano. Even a few inches can signal building pressure. Mount St. Helens is a volcano in Washington. It erupted in In the months leading up to the explosion, people saw steam and ash rising from the top of the mountain. The month before Mount St. Helens erupted, one side of the mountain began to bulge. The bulge grew rapidly. Then, it exploded with steam, hot gasses, pieces of rock, ash, and black smoke. Thankfully, most people had left the area before the explosion.

5 Earthquakes In an earthquake, the ground suddenly begins to shake. Remember the role the huge rock plates play in volcanoes? The plates are stars of earthquakes, too. Sometimes two plates bump into each other. They get stuck. They cannot move. A lot of energy builds up. At some point, the stored energy becomes so strong that the plates break apart. When this happens, there is an earthquake. The ground shakes as the energy is released in waves. It is like throwing a rock into a pond. Ripples extend out from where the rock landed. Scientists measure the size of an earthquake with a special instrument. It is called a seismograph. The seismograph draws a line during an earthquake. A line with tiny wiggles means the earthquake was small. A line with a lot of tall wiggles means the earthquake was big. In a big earthquake, people thousands of miles away can feel the shaking. Seismograph

6 An earthquake itself does not harm a person, although the ordeal can be frightening. However, earthquakes can damage buildings. They can lean and even fall, causing harm to people in the building or nearby. Earthquakes can also break dams and cause a flood. They can start fires. One of the worst earthquakes in history happened in San Francisco. It was just after five o clock in the morning on April 18, The earthquake broke gas lines in the city. That started fires. The city burned for three days. The fire destroyed about 500 city blocks. Earthquakes can happen anywhere, but most of them occur in two areas. Many earthquakes take place in the Ring of Fire. Earthquakes can happen at any time of the year, and they are almost impossible to predict. San Francisco, 1906

7 Tsunamis A tsunami is what many people call a tidal wave. It is a series of tall, fast moving waves. Most tsunamis happen when there is an earthquake under the ocean. You will probably not be surprised to learn that most tsunamis happen in the Ring of Fire in the Pacific Ocean. Picture the rock in the pond again. When an earthquake happens under the ocean, the seafloor shakes. The waves spread out in circles that get wider and wider. A tsunami can travel as fast as a jet at up to 500 miles an hour. It can be as tall as a three-story building. When it hits the shore, huge waves can destroy entire towns built on a coast. When an earthquake occurs and a tsunami begins, the waves at sea are not high, so they are not seen. However, scientists give warnings when they detect an earthquake under the water.

8 The warning system is focused on the Pacific Ocean. For this reason, when a tsunami occurred in the Indian Ocean in 2004, people were not warned. Many people in Indonesia, India, and Thailand died when the waves washed away their villages. The End