VOLCANOES VOCABULARY Magma molten rock usually contained in

VOLCANOES

VOCABULARY • Magma : molten rock (usually contained in a magma chamber) • Eruption: when anything is ejected from volcanic vent • Lava : Magma once at the surface of the earth • Pyroclastic debris: fragments created by volcanic explosions • Vent : opening in earths surface through which a volcanic eruption takes place

WHAT IS A VOLCANO? • Hill or mountain created by the extrusion of lava or rock fragments from a vent

WILL THEY ERUPT? • Volcanoes can be active, dormant, or extinct • An active volcano is one that has had an eruption in historical times (in the last few thousand years) • A dormant volcano is one that has erupted in historical times and has the potential to erupt again, it just hasn’t erupted recently. • An extinct volcano is one that scientists think probably won’t erupt again.

THE INSIDE OUT • Provide a lot of information on the workings of the earth’s interior • Vary in nature (explosive or not) • Strong correlation exists between chemical composition of magma and violence of eruption • Size and shape also depends on chemistry of lava

TYPES OF VOLCANOES 1. Shield Volcano 2. Composite Cone 3. Cinder Cone

SHIELD VOLCANOES • Broad, gently sloping cones made from solidified lava flows • During eruptions, lava flows widely and thinly spreading out (giving the “shield” appearance) • Relatively non-violent as lava is fairly fluid (runny) • Usually the largest volcanoes (height and width)

HAWAII SHIELD EXAMPLE • Growing Hawaii…. • The tallest volcano on Earth is Hawaii’s Mauna Kea, with an elevation of 4, 207 meters. It’s only a little bigger than the largest volcano on Earth, Mauna Loa with an elevation of only 4, 169 meters. Both are shield volcanoes that rise up from the bottom of the ocean. If you could measure Mauna Kea from the base of the ocean to its peak, you’d get a true height of 10, 203 meters (and that’s bigger than Mount Everest).

CINDER CONE VOLCANO • Volcano made from pyroclasts (fragment of rock made by volcanic explosion) • Very steep slops (in contrast to Shield variety) • Most ejected material is collected on slopes of volcano and bound by gravity (can only get so steep) • Generally have short lives (very few eruptions) • Generally very short (few higher than 500 m) • Very explosive, but chambers usually small)

COMPOSITE CONE • Volcano made from alternating layers of pyroclasts and rock solidified from lava flows • Slopes come in variety of steepness (a mix of shield and cinder) • Lava flows fatten, while pyroclasts build up • Built over long spans of time (long time between eruptions usually), so generally very large • Usually the most destructive (pyroclastic flows, tephra, lots of ejected material)

WHAT USED TO BE KRAKATOA… • When Krakatoa blew, the whole island exploded (hence the loudest sound ever on Planet Earth) • What is left, are flanks of the original volcano, and where the caldera used to be is now water between the “new” islands

• Nova: Meet the Volcanoes

DESTRUCTIVE NATURE OF VOLCANOES 1. Pyroclastic Flows 2. Lahars 3. Tephra

PYROCLASTIC FLOWS • Also known as Nuee Ardentes • Fast-moving current of extremely hot gas • Travel away from a volcano at speeds generally as great as 700 km/h • The flows normally hug the ground and travel downhill, or spread laterally under gravity.

PYROCLASTIC FLOWS Video

LAHARS • Mudflow and debris flow composed of pyroclastic material, rocky debris, and water • The material flows down from a volcano, typically along a river valley Where does the liquid come from? • Burst dam • Glacial, snow melt (very quickly since I hear lava is fairly hot? ? )

LAHARS • Lahar

TEPHRA • Fragmental material produced by a volcanic eruption regardless of composition, fragment size or emplacement mechanism (Rock Bombs)

NEAT FACTS • the cinder cone volcano Paricutin appeared in a Mexican cornfield on February 20, 1943. Within a week it was 5 stories tall, and by the end of a year it had grown to more than 336 meters tall. It ended its grown in 1952, at a height of 424 meters. • The biggest volcano in the solar system: Olympus Mons, on Mars, is a giant shield volcano that rises to an elevation of 27 km, and it measures 550 km across. • The furthest spot away from the center of the Earth is the volcano Chimborazo in Ecuador. That’s because the Earth is spinning in space and is flattened out. Points at the equator are further from the center of the Earth than the poles. And Chimborazo is very close to the Earth’s equator.

THE BIGGEST AND BADDEST! • Worst Eruptions of all time! (on zip drive) • Types: http: //www. youtube. com/watch? v=Hdh. ARb 2 PGq. A&safe=active