Volcanic Eruptions Chapter 3-3

Inside a Volcano

Volcanic Eruptions As magma rises towards the surface, pressure decreases Pressure on dissolved gases decreases causing bubbles to expand Force of expanding gases pushes magma through pipe and out of vent Type of eruption depends on silica content and viscosity

Quiet Eruptions Occur with magma with low silica (low viscosity, flows easily) Gases in magma flow out gently Can flow for many kilometers Produces both pahoehoe and aa Ex: Mt. Kilauea in Hawaii

Explosive Eruptions Occurs when magma is high in silica (high viscosity, thick and sticky) Magma builds up in pipe Trapped gases increase in pressure until they explode Lava cools quickly into different sized fragments of rock (ash, cinders, bombs) Causes pyroclastic flow Forms pumice and obsidian

Mt. St. Helens

Volcanic Hazards Cause fires Clouds of deadly gases and ash Trigger landslides

Life Cycle of a Volcano Active Dormant Extinct

Monitoring Volcanoes Geologists – Use tiltmeters – monitor gases – look for rise in groundwater temperature – monitor nearby earthquakes ***A little more successful than predicting earthquakes