Plate tectonics, volcanoes,and earthquakes

Ken HudnutKen HudnutU. S. Geological SurveyU. S. Geological Survey

Mr. Hajek’s 4th-grade classroomParadise Canyon Elementary SchoolLa Canada, California 3 October 2003

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Plate tectonics, volcanoesPlate tectonics, volcanoesand earthquakesand earthquakes

• Part 1Part 1 - plate tectonics - plate tectonics

• Part 2Part 2 - volcanoes - volcanoes

• Part 3Part 3 - earthquakes - earthquakes

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Movie by T. Atwater, UCSB

Part 1. Plate TectonicsPart 1. Plate Tectonics

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Motion betweenthe plates causesearthquakes andvolcanoes

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Earthquakes and volcanoes are Earthquakes and volcanoes are driven by plate tectonic motiondriven by plate tectonic motion

• As a plate subducted, As a plate subducted, the Cascades the Cascades volcanoes and San volcanoes and San Andreas fault were bornAndreas fault were born

• The subducting plate The subducting plate melts and the magma melts and the magma rises up to form rises up to form volcanoesvolcanoes

• The plates sliding past The plates sliding past each other make the each other make the active transform faultsactive transform faults

Movie by T. Atwater, UCSB

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Worksheet on Worksheet on Plate EdgesPlate Edges

• Plate edges are of three typesPlate edges are of three types

• Plates pull away from each otherPlates pull away from each other

• Plates push towards each otherPlates push towards each other

• Plates slide past each otherPlates slide past each other

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Part 2. VolcanoesPart 2. Volcanoes

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Eruption of Stromboli, Italy

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Motion betweenthe plates causesearthquakes andvolcanoes

This is really bad news for people (like us!) living around the Pacific Rim, also known as the Ring of Fire

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Why do volcanoes erupt?Why do volcanoes erupt?

• Pressure builds up Pressure builds up because of heat and because of heat and trapped gas bubblestrapped gas bubbles

• Cracks open and lava, Cracks open and lava, steam and ash blast outsteam and ash blast out

• Sticky magma makes Sticky magma makes tall cone-shaped tall cone-shaped volcanoes (like Merapi)volcanoes (like Merapi)

• Runny magma makes Runny magma makes low, broad volcanoes low, broad volcanoes (like Kilauea, Hawai’I)(like Kilauea, Hawai’I)

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MerapiMerapivolcano,volcano,JavaJava

Strato-volcanoeserupt igneous rocks!

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WestdahlWestdahlvolcano,volcano,AlaskaAlaska

QuickTime™ and aBMP decompressorare needed to see this picture.Volcanoes inflatewith magma, anddeflate with lava

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Worksheet on Worksheet on Ring of FireRing of Fire

• Plates crash into each other, causing Plates crash into each other, causing high mountains and low ocean floor high mountains and low ocean floor called trenchescalled trenches

• Deepest trench is the Marianas (esp. at the Deepest trench is the Marianas (esp. at the ‘Challenger Deep’ location shown on map)‘Challenger Deep’ location shown on map)

• Highest mountain is Mt. EverestHighest mountain is Mt. Everest

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Worksheet: hot spot track - islands cool, erode, & sink

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Part 3. EarthquakesPart 3. Earthquakes

Earthquakesare a globalproblem

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Earthquakes are driven by plate Earthquakes are driven by plate tectonic motiontectonic motion

• In the past 5 million In the past 5 million years, this motion years, this motion has been steady at has been steady at about 2 inches per about 2 inches per year year (that’s 15 feet (that’s 15 feet per century or 30 per century or 30 miles per million miles per million years!)years!)

• Yes, LA will be in Yes, LA will be in San FranciscoSan Francisco

• No, LA will not fall No, LA will not fall into the seainto the sea

Movie by T. Atwater, UCSB

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Earthquakes are Earthquakes are not onlynot only California’s problem California’s problem$30M of oil each day!

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Houston, we have a problem…Houston, we have a problem…

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Southern California is the nation’s most Southern California is the nation’s most dangerous place for earthquakes - why?dangerous place for earthquakes - why?

Silver linings:State-of-the-art earthquake monitoring arraysMany of the world’s best researchers work within this natural laboratory

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The San Andreas faultThe San Andreas fault

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San Andreas faultSan Andreas fault• Most of the plate Most of the plate

boundary motionboundary motion• 1685, 1812, 1857 eq’s1685, 1812, 1857 eq’s

• Big Bend compressionBig Bend compression• 1971 Sylmar (M 6.7)1971 Sylmar (M 6.7)• 1994 Northridge (M 6.7)1994 Northridge (M 6.7)

• SoCal is now heavily SoCal is now heavily ‘wired’ (much like ‘wired’ (much like Japan & Taiwan)Japan & Taiwan)• SeismicSeismic• GPSGPS

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GPS

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‘A rip in the desert canvas’- Los Angeles Times

Katherine Kendrick, USGS

Chris Walls, Earth Consultants International

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Flying the fault line…Flying the fault line…

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Conclusions:Conclusions: • Earth is a very active Earth is a very active planet - that’s both a planet - that’s both a good and bad thinggood and bad thing

• Humans can survive Humans can survive despite natural hazards - despite natural hazards - tragic losses from tragic losses from volcanoes & earthquake volcanoes & earthquake are not inevitableare not inevitable

• Natural beauty results Natural beauty results from plate tectonics - we from plate tectonics - we can study & understand can study & understand the world around usthe world around us