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Igneous Activity

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Michael Littleton

on 8 November 2011

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Transcript of Igneous Activity

Igneous Activity Volcanoes Factors of Eruption Aspects of Eruptions Types of Volcano Intrusive Activity Relation to Plate Tectonics Plutons Magma Actions at Boundaries Actions Inside Plates Viscosity Dissolved Gases Temperature Maple Syrup Resistance to Flow More or Less viscous than water? The MORE viscous The LESS smoothly it flows The LESS viscous The MORE smoothly it flows Mostly affects the viscosity HOTTER substances are MORE viscous COOLER substances are LESS viscous Composition Silica-rich lava is very viscous Basaltic lava is NOT very viscous As magma approaches the surface The pressure on it begins to release Low viscosity allows the gas bubbles to escape easily, so leads to a quiet eruption High viscosity magma "holds" the gases and causes a more explosive eruption Rate of Flow Gases Speed How it hardens The fastest lava flows at rates from 10 to 300 meters per hour As basaltic lava hardens, it forms a skin that wrinkles as the lava below it keeps moving Pahoehoe A'a Sometimes it has a rough, jagged surface Make up 1% to 6% of total weight of lava Mostly made of water vapor and carbon dioxide Pyroclastic Material Material blown away from an eruption by wind or force of explosion Types LAPILLI BLOCK BOMB pieces of pyroclastic material smaller than a walnut larger pieces that are hardened larger pieces that are still soft Anatomy Shield Cinder Cones Composite Cones Conduit Volcano Crater Form Determination Warrior's Shield Examples Composition Form "Stratovolcanoes" Form Location Danger Location a natural pipe that forms to deliver lava to the surface and relieve pressure a mountain formed by repeated eruptions of lava or pyroclastic material a steep-walled inverted cone at the summit of the volcano The size, shape, and danger of a volcano is determined mostly by composition So-named because the general shape is like a Made of very fluid lava that can't "stand" up Hawaii Mount Kilauea So it runs outward and makes a very large, shallow shape Iceland Mostly just a pile of loose pyroclastic material Single eruption Steep, even cone Usually found on the side of other volcanoes But sometimes found in "volcanic fields" A large, nearly symmetrical structure Made of both lava and pyroclastic material Not to be messed with... Usually, the most dangerous type of volcano Pyroclastic flow Think, mudflow, but hot Comes from MASSIVE pressure creating an adundance of pyroclastic material Mostly found in the Pacific Rim in the "Ring of Fire" Formations Caldera Necks and Pipes Lava Plateaus A large depression in a volcano Happens in... Composite Cones and Shield Volcanoes after an explosive eruption when the magma chamber drains too much As magma moves through the conduit, what happens to the inside of the "pipes"? "Kinda melty?" Metamorphic rock forms When everything else around it erodes away... When eruptions happen in volcanoes, you know what it looks like When magma comes out of the ground from fissures with low viscosity which becomes (over time) Definition Sills Laccoliths Dikes Batholiths Chunks of igneous rock formed intrusively Does not need to be exposed But exposure can occur because of UPLIFT or EROSION Formed by magma squeezing into tight sheets between layers of bedrock When a sill begins to form with highly viscous magma The magma "backs up" and the pressure pushes up on the ground above A fissure leads to lava plateaus on the surface But when the fissure "dies" and cools it hardens into a dike Whole magma chambers sometimes lose their heat and pressure without erupting The magma hardens into igneous rocks...very big rocks Water Heat Pressure Depth Friction The deeper you go The hotter the temps At subduction zones, rock rubs against rock Under pressure, melting points are higher So as pressure is reduced by uplift, rock suddenly melts Rock with water in it melts at lower temperatures So when rock with lots of water in it are put into the mantle (subduction) it forms magma
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