Volcanic Eruptions. Mafic Lava Dark colored Rich in magnesium and iron Formed from oceanic crust ...
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Transcript of Volcanic Eruptions. Mafic Lava Dark colored Rich in magnesium and iron Formed from oceanic crust ...
Volcanic EruptionsVolcanic Eruptions
Mafic Lava Dark coloredRich in magnesium and ironFormed from oceanic crustCools rapidly
Felsic Lava
Light coloredRich in silicaFormed from continental crust
Eruptions
Composition of lava determines the force of the eruption
Oceanic Eruptions
Erupt on the ocean floor and oceanic islandsMafic lava
Very hotVery thin (watery)Flows easily
Continental Eruptions
Erupt on the landFelsic lava
CoolerThickerContains large amounts of gases
Carbon dioxide and water vaporExplosive
Mafic Lava
Pyroclastic material (tephra)-rock fragments ejected from volcanoesVolcanic ash- less than 2 mmVolcanic dust- less than .25 mmBoth can travel around the Earth in the
atmosphere
Volcanic Cones
Piles of volcanic material around the vent
Volcanic cones
Shield conesCover wide areasBroad at the baseGentle slopeQuiet eruptionsExample Hawaiian Islands
Shield cones
Volcanic cones
Cinder conesExplosive eruptionsVery steep slopesRarely more than a few hundred meters high
Cinder cones
Volcanic cones
Composite conesDevelop into high volcanic mountainsAlternating types of eruptionsExamples: Mount Fuji, Mount Hood, Mount St.
Helens
Composite cones
Crater
Funnel shaped pit at the top of a volcanic vent
Caldera
Large basin shaped depression caused by an explosive eruption Magma chamber below a vent, causing the
volcanic cone to collapse
Predicting Volcanoes
EarthquakesTemperature changes in rock around ventBulging of the surface of the volcanoChange in gases given off