Volcanoes

Volcanoes are wicked crazy manifestations that power the Earth. A volcano is a mountain that opens downward to a pool of molten rock below the surface of the earth. When pressure builds up, eruptions occur. Gases and rock shoot up through the opening and spill over or fill the air with lava fragments. Eruptions can cause lateral blasts, lava flows, hot ash flows, mudslides, avalanches, falling ash and floods. Volcano eruptions have been known to knock down entire forests. An erupting volcano can trigger tsunamis, flashfloods, earthquakes, mudflows and rockfalls. Active volcanoes in the U.S. are found mainly in Hawaii, Alaska, California, Oregon and Washington. The greatest chance of eruptions near areas where many people live is in Hawaii and Alaska. The danger area around a volcano covers about a 20-mile radius. In May 18, 1980, Mount St. Helens erupted in Washington state. It killed 58 people and caused more than $1,000,000,000 in property damage.Fresh volcanic ash, made of pulverized rock, can be harsh, acidic, gritty, glassy and smelly. The ash can cause damage to the lungs of older people, babies and people with respiratory problems.

Volcanoes are really mountains that build taller and taller, with time, as they erupt. That means that molten rock, magma, comes from within the earth and erupts onto the surface. The volcano might be explosive and produce ashes or be effusive and produce lava. The explosions are usually first because there are lots of gases inside the magma. When you have a can of pop, you do not see any bubbles of gas, but when you open it, bubbles form almost instantly. Once the gas bubbles have all escaped, the soda is flat and sick. Once the magma is flat, a lava flow comes out. Most of the volcanoes from around the Pacific Ocean are composite, which means that there are layers of ashes and lava. Most volcanoes are 10,000 to 100,000 years old,it takes time for them to grow big.Inside the crater of a volcano there is nothing alive and many small holes that release nasty gases. There are many colorful minerals being deposited from the gases as they cool. The most important gas is water, and then carbon dioxide. These two important gases are not poisonous. Sulfur dioxide, hydrogen chloride, and hydrogen fluoride are blown in the air as well. They are strong poisons and cause pollution problems.

Volcanoes make many different types of rocks. For example, black shiny rocks with only a few crystals are usually basalt. The opposite white shiny rock with many crystals and often many bubble holes inside the rock is rhyolite. In between are andesites, which are light gray and usually have large box-shaped crystals called plagioclase. They come from the Andes Mountains, which is a chunk of volcanoes in South America. The Hawaiian islands are mostly made up of basalts, so they are famous for their sweet black-sand beaches.We know of at least 1,500 active volcanoes around the world. That is a big increase from the number that we used to think was correct. It means that more dudes are searching the earth for them. A graph of the number of volcanoes of the world shows that it goes up just about as fast as the number of people on the earth does.The lower 48 states in the U.S. have about 40 volcanoes that we think have had recent activity, so they must be considered as active volcanoes. In Alaska, they have about 60 volcanoes. Most of the important eruptions and disasters have happened at mountains that were not even recognized as being volcanoes.On the surface of the earth, we know of at least 1,500 active volcanoes. We would estimate the ocean contains 10,000 volcanoes! Scientist just don't have much chance to see them because they are hidden away! Submarine volcanoes are very different from the volcanoes that are above sea level. Water has a higher pressure than air. This higher pressure can cause an underwater, explosive volcanic eruption. One famous example of an underwater explosive eruption is Surtsey, a new volcano off the south shore of Iceland. When Surtsey erupted it punched through the sea and became an island!The biggest volcano in the world is probably Mauna Loa, in Hawaii. It rises off of the seafloor to 13,000 feet above sea level or about 29,000 feet above the seafloor. Another huge volcano is Mt. Etna on the island of Sicily, in Italy.The oldest volcano is probably Etna and that is about 350,000 years old. Most of the active volcanoes that we know about seem to be less than 100,000 years old. Volcanoes grow because lava or ash builds up on the volcano, adding layers and height.Some very important volcanoes are not mountains at all. They look like deep lakes because they have had huge eruptions that make the ground sag down.About 500 million people live close to active volcanoes. People may think that it is beautiful to live next to one, but it is still very dangerous.

[|Volcano vid.] [|vid] Some cool sites 1 http://www.uhh.hawaii.edu/~csav/quicktime/LightningWeb.mov 2 http://encarta.msn.com/encyclopedia_761570122_5/Volcano.html 3 http://ngm.nationalgeographic.com/2007/09/vesuvius/decade-volcano-map-interactive 4 [|http://abcnews.go.com/Technology/popup?id=133588]5 5 http://volcano.oregonstate.edu/education/index.html

Work Cited < http://channel.nationalgeographic.com/series/earth-the-biography/3128/Overview#tab-facts >