Volcanic ActivityVolcanic Activity

Magma Reaching the Magma Reaching the SurfaceSurface

Materials of asthenosphere under great Materials of asthenosphere under great pressurepressure

Magma less dense than surrounding Magma less dense than surrounding rockrock

Magma rises until it reaches the Magma rises until it reaches the surface or becomes trapped by rock surface or becomes trapped by rock layerslayers

A Volcano EruptsA Volcano Erupts

Dissolved gases in magma are under Dissolved gases in magma are under tremendous pressuretremendous pressure

As magma rises pressure decreasesAs magma rises pressure decreases

Gases dissolved in magma rush out, Gases dissolved in magma rush out, carrying magma when an opening carrying magma when an opening develops in weak rock on the surfacedevelops in weak rock on the surface

Inside a VolcanoInside a Volcano

Characteristics of MagmaCharacteristics of Magma

Force of volcanic eruption impacted Force of volcanic eruption impacted by:by:– Gas dissolved in magmaGas dissolved in magma– Thickness of magmaThickness of magma– TemperatureTemperature– Silica contentSilica content

Characteristics of MagmaCharacteristics of Magma

Some magma thick- flows slowlySome magma thick- flows slowly Some more fluid- flows easilySome more fluid- flows easily Viscosity describes a liquids Viscosity describes a liquids

resistance to flow- higher viscosity, resistance to flow- higher viscosity, greater resistancegreater resistance

http://www.seed.slb.com/en/scictr/lab/visco_exp/index.htm

Characteristics of MagmaCharacteristics of Magma

Temperature impacts thickness- Temperature impacts thickness- hotter, more fluidhotter, more fluid

More silica- thicker magmaMore silica- thicker magma– High silica- light lava, too sticky, doesn’t High silica- light lava, too sticky, doesn’t

flow far, forms rhyolite, pumice, & flow far, forms rhyolite, pumice, & obsidianobsidian

– Low silica- flows easily, dark colored, Low silica- flows easily, dark colored, forms basaltforms basalt

Types of EruptionsTypes of Eruptions

Quiet EruptionsQuiet Eruptions– Quiet eruption if magma flows easilyQuiet eruption if magma flows easily– Gases bubble out gentlyGases bubble out gently– Lava oozes quietly from ventLava oozes quietly from vent– Ex. Hawaii, IcelandEx. Hawaii, Iceland– Forms from basaltic material, low in Forms from basaltic material, low in

silicasilica– Type of crust?!?Type of crust?!?

Types of Volcanic EruptionsTypes of Volcanic Eruptions

Explosive eruptionsExplosive eruptions– Thick & sticky magma- explosive eruptionThick & sticky magma- explosive eruption– Dissolved gases can’t escape, pressure Dissolved gases can’t escape, pressure

builds up, it explodesbuilds up, it explodes– Magma pushed out of volcano w/incredible Magma pushed out of volcano w/incredible

forceforce– Pyroclastic flow hurls ash, cinders, bombsPyroclastic flow hurls ash, cinders, bombs– Forms from granitic material, high in silicaForms from granitic material, high in silica– Crust type?!?Crust type?!?

Stages of a VolcanoStages of a Volcano

Active- erupting or shows signs of Active- erupting or shows signs of erupting in near futureerupting in near future

Dormant- sleeping, expected to Dormant- sleeping, expected to awaken in future & become activeawaken in future & become active

Extinct- unlikely to erupt againExtinct- unlikely to erupt again

Other Volcanic ActivityOther Volcanic Activity

Hot springHot spring GeyserGeyser Geothermal energyGeothermal energy