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Volcanoes

Volcanoes. Introduction .

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Volcanoes

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  1. Volcanoes

  2. Introduction Volcanoes occur along the earth's tectonic plates where molten rock is forced upward from magma reservoirs deep in the earth. The magma may be fifty to one hundred miles below the ground. As the magma rises, it gives off gases that cause an explosion in the vents of the volcano. Lava can reach temperatures of over 2000 degrees F. Molten rock, dust, and gases push through the opening in the earth's crust and form a mountain. A violent explosion can cause the top of the volcano to blow off leaving a deep crater.

  3. Fissure • A fissure is a crack in the ground that lava comes out of. • Sometimes when lava cools is goes back into the fissure where it came from. • Fissures can also erupt for a period of hours or days.

  4. Vents • Vents are openings in the earth where magma and gases pour into the ground or the atmosphere. • Vents may have a circular-shaped structure,or a tiny ground crack.

  5. Ash • Volcanic ash is not like other ash because it is hard and doesn’t dissolve in water. • Ash is very small and is made of rock, minerals, and volcanic glass pieces. • Ash is created when a volcano erupts and magma splits in small pieces. • Hot ash and gas form a cylinder above the volcano and creates a gray cloud.

  6. Magma • Magma is molten rock underneath the earth. • Magma collects inside the magma chamber before the volcano erupts. • Magma consists of a a liquid portion(melt) and a solid portion made of minerals(crystallized from the melt). • When the volcano erupts onto the earth’s surface, the magma becomes a liquid.

  7. Caldera • A caldera is a big, circular depression at the top of a volcano. • A caldera is formed when magma is disputed, or erupted, from the vent. • Calderas are different from craters, which are smaller. • The removal of large volumes of magma may result in the loss of structural support, causing the caldera to form after the explosive excavation of rocks. • Caldera is the Spanish word for caldron.

  8. Lava • Lava is molten rock that reaches the earth’s surface through a volcano or fissure. • Magma becomes lava when it reaches the earth’s surface • All magma and lava consist mainly of a liquid, along with solid rock and gaseous matter. • Lava is from the Italian word for stream: lavare -to wash

  9. Lava Flow • Lava flows are masses made of melted rock called magma. • It pours onto Earth’s crust during an effusive eruption. • Lava flows come in various shapes and sizes as all volcanoes are different. • The viscosity of lava is one hundred thousand times that of water. • The viscous rock can flow many miles before cooling.

  10. Lava Dome • A lava dome is a round, steep-sided mound created by the eruption of high-silica lava. • Lava domes stick to the side of volcanoes before cooling. • The dome may include one or more lava flows. • Domes may reach heights of several hundred meters, and they can grow slowly and steadily grow for months or years.

  11. Volcanic Eruptions

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