volcanoes

earth Earth is different from all other planets in the solar system. We have vast quantities of water on our planet, and we have oxygen to breath. We have soil in which planets grow. There is a blanket of air around the earth, called the atmosphere that protects us from the harmful ultraviolet rays of the sun.CrustThis is the outermost layer of earth. Continents and oceans lie on this layer. It is made of rocks and contains everything essential for life on earth.MantleThis layer is below the crust and has some hot molten rock below a very thick layer of solid rock. It is from here that magma comes out, when a volcano erupts. This layer contains a lot of iron and magnesium. Core This layer, below the mantle, forms the center of the earth. The outer part of the core is in a molten state like the lower part of the mantle. It contains iron and nickel. The innermost part of the core is a solid. VOLCANOES, EARTHQUAKES, and tidal waves The earth is usually a peaceful place, but sometimes natural disasters can upset life. We have no control over these happenings, but knowing they are possible will help us take better care of ourselves when they occur . Some of these phenomena are volcanic eruptions, earthquakes, and tidal waves. These happen due to movements within the earth.VolcanoesVolcanoes are cracks in the earth’s crust out of which molten magma erupts. This magma comes from the mantle of the earth and reaches the crust through cracks. Volcanoes are usually in the form of conical mountains.According to the nature of the volcano, there are three types : active ,dormant ,and extinct volcanoes. Active volcanoes.Active volcanoes are those that may erupt any time or have erupted in the recent past.Many active volcanoes are found around the Pacific Ring of Fire’.Mount Vesuvius, Mount Fuji, and Mount Erebus are some well known volcanoes.Dormant volcanoes are those that have not erupted in a long time but may erupt in the future.Extinct Volcanoes are those that have stopped erupting. Some islands have been formed by the eruption of the undersea volcanoes. Barren Islands The barren island is an active volcano in the Andaman Islands. It has been erupting from 1994. When it is erupted in 1991, it spewed lava continuously for six months!A lot of pressure underground pushes up the molten rock. The molten rock rushes out through a vertical tunnel called a vent and fills a hollow crater at the top. This hot magma that gushes out is called lava. As lava cools, it solidifies and forms rocks.Volcanoes on other celestial bodies.There are volcanoes on other planets and satellites too. Venus is believed to have active volcanoes. Mars has extinct volcanoes. In fact, it has the biggest crater in the solar system, called the Olympus Mons.Tidal wavesTidal wave is the common name for a tsunami. Tsunami is a Japanese word meaning harbor wave. Tidal waves have nothing to do with the tide, but are so called because they look like high tide, rushing towards the coast. Tidal waves are caused by undersea earthquakes, volcanic eruptions, landslides, etc. In a tidal wave, large amounts of water move. The water moves at a great speed and as the waves reach the land, they swell up into gigantic waves. If one happens to look at the sea when a tsunami is approaching, one feels as though the sea level has raised a lot.