10-2) The Nature of Volcanic Eruptions
No description yet. This curated deck is ready for daily study.
Card preview (24)
what are the factors affecting eruptions?
viscosity and dissolved gases
what is viscosity?
the substance’s resistance to flow
high viscosity ____ flow? low viscosity ____ flow?
resists easily
more viscous is? less viscous is?
thick and more violent thin gentle eruptions
more silica =
greater viscosity, more violent
granitic magma has…?
higher silica, thickness causes pressure build up which leads to explosive eruptions.
basaltic magma has/is…?
less silica, less viscous, quiet eruptions
what are dissolved gases?
gases trapped in the magma provide the force to propel lava out the vent
explain what happens when carbon dioxide gas is dissolved in the liquid? (like a soda can)
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.
hot basaltic lava is?
usually fluid, (low silica, low viscosity), runs down sides of volcanoes
what are the two types of basaltic lava?
Pahoehoe lava - hotter, fast-moving basaltic lava “twisted rope”, smooth surface. Aa lava - cooler, slower-moving, “spiny” rough surfaces.
what are pyroclastic materials?
particles produced in volcanic eruptions, cools quickly and hardens into different sizes.
explain the pyroclastic materials from smallest to largest.
volcanic ash (smallest pieces), cinders (pebble-sized), blocks (larger-sized), bombs (blocks as glowing lava)
what are the volcanic hazards?
lava flows, volcanic ash, pyroclastic flows, and mudflows
what is a pyroclastic flow?
scorching mixture of glowing volcanic particles/gases that sweeps fastly down volcano’s flanks
what is lahar?
when water-soaked volcanic ash and rock slide rapidly downhill, ice and snow melted by an eruption/heavy rains can trigger it
what is a crater?
steep bowl-shaped area that may form at the top of the volcano around central vent
what is lava flow?
area covered by lava as it pours out of a vent. obsidian - lava cools very quickly (smooth/glossy). pumice - gases trapped in fast cooling lava
explain shield volcanoes! what type of eruption, what lava/magma, how well it flows, shape.
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
explain cinder cones! what type of eruption, what lava/magma, how well it flows, shape.
explosive eruption, high viscosity (high silica), basaltic lava, flow slowly, lava cools and hardens into tephra, vary in size. steep-sided.
explain composite cones! what type of eruption, what lava/magma, how well it flows, shape.
vary between quiet and violent, most dangerous, alternating layers (between shield and cinder), andesitic magma, tall cone-shaped, found in subduction zones
volcanic activity can volcanic landforms like?
calderas, volcano necks, and lava plateaus
what are calderas?
huge hole left by collapse of a volcanic mountain. enormous eruption empties vent and chamber and mountain becomes hollow and collapses.
what are volcanic necks?
when magma hardens in a volcano’s pipe. softer rock of tephra around pipe wears away.