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Volcanoes. Chapter 8 Section 2 Pgs. 219 - 224. How volcanoes form. Fissure – crack in the crust, where a conduit forms which acts like a pipe magma travels through Magma is forced upward toward Earth’s surface by denser surrounding rock
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Volcanoes Chapter 8 Section 2 Pgs. 219 - 224
How volcanoes form • Fissure – crack in the crust, where a conduit forms which acts like a pipe magma travels through • Magma is forced upward toward Earth’s surface by denser surrounding rock • Causes an eruption where magma, solids, and gas are spewed out to form cone-shaped mountains
Lava – magma flowing on Earth’s surface through a vent or opening • Craters – circular hole of volcano • Tephra – bits of rock or solidified lava dropping from the air • Reservoir – where magma is stored • Summit – highest point • Vent - opening where lava flows
Where Plates Collide • Volcanoes form by a collision of large plates of crust and upper mantle • Oceanic plate sinks under another plate, rocks melt, forms chambers of magma
Volcanic Risk Maps • Used to prepare people and visitors about unsafe areas
Volcanic Eruptions • Violent or quiet • Lava high in silica produces explosive eruptions • Lava high in iron and magnesium produces more fluid eruptions • The amount of water vapor and gases impact eruptions
Shield Volcanoes • Largest type of volcano • Gently sloping volcano that emits mostly basaltic lava (very fluid) that is long-lasting, gentle eruptions, explosions minimal
Mauna Loa, HI • Made from 5 shield cones • Largest volcano on Earth – Mauna Loa in Hawaii, 6 miles tall
Cinder Cone Volcanoes • Smallest volcano, very steep with large craters • Formed by moderate to explosive eruptions of tephra
Cinder Cone Volcano • Pu ‘ u ka Pele – Hawaii • Mostly found on the sides of shield volcanoes
Composite Volcano • Steep sides • Formed by alternating layers of violent eruptions of tephra and quieter eruptions of lava
Composite Volcano • Most active volcano – Mt. St. Helens in the western part of the state of Washington
Extreme Volcanoes • Largest volcano in the Solar System – Olympus Mons on Mars, 17 miles tall and over 320 miles across.
Questions • Hawaii is an example of what type of volcano? • What are the three types of material that a volcano can emit? • The eruption of Mount Vesuvius buried what town in 79 A.D.? • How did people die in the aftermath of the famous Mount Vesuvius eruption? • Mount St. Helen’s erupted violently in 1980. On what continent is this volcano found?