Volcanic Activity Chapter 3 Section 2 Pages 93

Volcanic Activity Chapter 3 Section 2 Pages 93 -102 S

How Magma Reaches Surface S Created in the Asthenosphere S Will rise through any cracks in rock above S During a volcanic eruption magma rush out, once on surface gases from the magma will bubble out S Just like a bottle of soda when you open it

Inside a Volcano S Magma Chamber S Pocket of magma under the volcano S Pipe S Long tube connecting magma to the earths surface S Vent S Spot where magma will leave the vocano

Characteristics of Magma S Thickness of magma S Thicker the Magma the slower it will move S Temperature of magma S Hotter the magma the more fluid it will be S Silica S High is light in color and to thick to move very far S Low is dark in color and flows readily

Types of Volcanic Eruptions S Magma influences how it will erupt S Silica content will determine whether the volcanic eruption is quiet or explosive

Quiet Eruptions S Forms when magma flows easily S Magma will bubble out gently S Magma can flow many kilometers from the vent S Produce two different types lava S Pahoehoe S aa

Pahoehoe

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Explosive Eruptions S Pressure builds up in the volcano’s pipe S When gases build up enough pressure until it explodes S Breaks lava into fragments that quickly cool and harden S Smallest pieces are volcanic ash S Cinders are pebble sized S Largest sizes can range from a baseball up to a car S Called bombs S Pyroclastic flow is when all three occur from an eruption

Stages of a Volcano S Activity can last less than 10 months or as long as 10 million years S Active S Dormant S Extinct

Other Types of Volcanic Activity S Hot spring S Groundwater is heated by nearby body of magma S Geysers S Rising hot water and steam become trapped S Pressure will build until mixture suddenly erupts on surface S Geothermal Energy S Steam from water gets trapped and spins a turbine

Monitoring Volcanoes S Usually give warnings a short time before it erupts S Tiltmeters and laser-ranging devices to detect ground movements S Also check water temperature near volcanoes S Monitor small earthquakes near a volcano S Caused by the movement of magma through the pipe of volcano

Volcano Hazards S Damage can be far from the crater S Quiet eruption S Lava can start fires and bury everything in its path S Explosive eruption S Send out ash, cinders, or bombs S Ash can be some of the most serious damage from a volcano

Review Questions S What are the stages that lead up to a volcanic eruption? S Compare and contrast quiet and explosive eruptions. S Describe some of the hazards posed by volcanoes.