Complete the paragraph below Lava begins as, which usually forms in the asthenosphere. The materials of the asthenosphere are under great pressure. Liquid magma is dense than the solid material around it. Therefore, magma flows upward into any cracks in the rock above. As magma rises, it sometimes becomes trapped beneath layers of rock. But if an opening in weak rock allows the magma to reach the surface an occurs.

Volcanic Eruptions

What happens?? Dissolved gases in magma are trapped and are under extreme pressure (keeps it from erupting) Magma rises Pressure of surrounding rock decreases Gasses can expand and form bubbles Pressure continues to fall and bubble get bigger and bigger (exert a LOT of force) Force from expanding gasess pushes magma from the chamber through the pipe until it flows or explodes out of the crater or vent

Kinds of Eruptions Depends on: -Silica Content -Viscosity Quiet Explosive

Quiet Eruptions Magma is low in silica Low viscosity and flows easily Gases bubble out gently Lava oozes from vents Some spurting Produce pahoehoe and aa

Damage from Quiet Eruptions Sets fires Buries anything in its path Covers large areas

Explosive Eruptions Magma has high silica content High viscosity making it thick /sticky Builds up (like a cork) holding in gases Explode when pressure is too much Lava shot into air breaks into fragments and cools in air Smaller pebble sized are cinders Larger pieces called bombs Pyroclastic flow is formed from gases, ash, cinders and bombs Forms pumice and obsidian

Damage from Explosive Eruptions Destroys anything in its path Pyroclastic cloud kills organisms Causes landslides and avalanches Stalls airplane engines

The Power of Volcanoes 1883 Krakatau 1902 Mount Pelee

The Power of Volcanoes 1982 Mt. St. Helens 2010 Eyjafjallajökull

The largest volcano in the solar system… clnzU

Monitoring Volcanoes Geologists have been more successful in predicting volcanoes than in predicting earthquakes. Measure changes in elevation caused by magma moving underground- Tiltmeter Can monitor escape of gases Temperature increase of ground water Small earthquakes around a volcano Does not predict type or power of eruption