chapter 10-2 Flashcards
(13 cards)
describe the factors that affect eruptions?
viscosity - substance’s resistance to flow
dissolved gases - gases trapped in the magma provide force to propel lava out the vent
describe granitic magma
high viscosity, resists flow, thick and more violent, higher silica
describe basaltic magma
low viscosity, flows easily, thin, gentle eruptions, less silica
what happens when carbon dioxide is dissolved in a liquid?
it expands and forms bubbles that rush to surface, under the surface gases are under great pressure. As magma approaches surface pressure is greatly reduced. When a volcano erupts it pushes magma up and remaining gases bubble out
describe the two types of basaltic lava
Pahoehoe lava - hot, fast, basaltic
Aa lava - cooler, slower, rough surfaces
what are pyroclastic materials? explain them from smallest to biggest.
particles produced in volcanic eruptions, cools quickly and hardens into different sizes.
Volcanic ash (smallest pieces), cinders (pebble-sized), blocks (larger-sized), bombs (blocks as glowing lava)
what is a pyroclastic flow?
Scorching mixture of glowing volcanic particles/gases that sweeps fastly down volcano’s flanks
what is a lahar?
When water-soaked volcanic ash and rock slide rapidly downhill, ice and snow melted by an eruption/heavy rains can trigger
what is a crater?
Steep bowl-shaped area that may form at the top of the volcano around central vent
explain the three types of volcanoes.
shield volcanoes: quiet eruption, basaltic lava, flat layers that are fluid like and flows well (low silica), layers harden on top of each other and build up broad volcanoes, gently sloping sides
cinder cones: explosive eruption, high viscosity (high silica), basaltic lava, flow slowly, lava cools and hardens into tephra, vary in size. Steep-sided
composite cones: vary between quiet and violent, most dangerous, alternating layers (between shield and cinder), andesitic magma, tall cone-shaped, found in subduction zones
what is a caldera?
huge hole left by collapse of a volcanic mountain. enormous eruption empties vent and chamber and mountain becomes hollow and collapses
what is a volcanic neck?
when magma hardens in a volcano’s pipe. Softer rock of tephra around pipe wears away
what is a lava plateau?
high relatively level landforms, erupts from cracks in crust instead of through a vent. thin, low viscosity, hot basaltic lava travels before cooling
