Dynamic EarthDynamic Earth

Dr. Jennifer WrightDr. Jennifer Wright

Shake, Rattle, ‘n RollShake, Rattle, ‘n Roll

• Plate Tectonics – the big picture, creation of the major geographic features of the Earth– Layers of the Earth– Plate Boundaries– Earthquakes– Volcanoes– Impact Craters

Layers of the EarthLayers of the Earth

• Inner core Inner core – Solid Fe, NiSolid Fe, Ni

• Outer coreOuter core– Liquid Fe, Ni Liquid Fe, Ni – Creates magnetic Creates magnetic

fieldfield• MantleMantle

– Magma, convectionMagma, convection• CrustCrust

– Thinnest, coldest Thinnest, coldest layerlayer

– Plates!!Plates!!

Plate TectonicsPlate Tectonics

• Framework for understanding most Framework for understanding most geographic features of the planet geographic features of the planet – Mountain ranges, volcanoes, earthquakesMountain ranges, volcanoes, earthquakes– Deepest point (Marianas Trench), Highest point Deepest point (Marianas Trench), Highest point

(Mt. Everest) caused by plate interaction(Mt. Everest) caused by plate interaction

• 3 kinds of plate boundaries3 kinds of plate boundaries– DivergentDivergent– ConvergentConvergent– TransformTransform

Divergent BoundariesDivergent Boundaries

• Are the result of “pulling” forces

• Have small earthquakes

• Create many normal faults

• Are usually on the opposite side of the plate from a convergent boundary

Convergent BoundariesConvergent Boundaries

• Collision of two plates• Have all the large

earthquakes• 90% of all earthquakes

happen here• Ocean-continent

collisions = subduction• Explosive volcanoes• Reverse faults

Transform BoundariesTransform Boundaries

• Are the result of parallel and opposite forces

• Have small to medium earthquakes earthquakes

• Create strike-slip faults

• Can cause streams to turn at right angles

EarthquakesEarthquakes

Mostly happen on plate boundariesMostly happen on plate boundaries90% happen on convergent boundaries90% happen on convergent boundaries

Seismographs can record Seismographs can record earthquakes from all over the world earthquakes from all over the world above 2.5-3 on magnitude scaleabove 2.5-3 on magnitude scale

Are a release of energy as two blocks Are a release of energy as two blocks move relative to each othermove relative to each other

Are measured on a logarithmic scale Are measured on a logarithmic scale (multiply by 10)(multiply by 10)

VolcanoesVolcanoes

Mostly created by melting of oceanic Mostly created by melting of oceanic plate in the subduction zone and by plate in the subduction zone and by hot spots in the mantlehot spots in the mantle

Explosive volcanoes associated with Explosive volcanoes associated with dissolved gases (Hdissolved gases (H22O) in lavaO) in lavaEx. Mt. St. Helen’sEx. Mt. St. Helen’s

Impact CratersImpact Craters Far fewer visible impacts Far fewer visible impacts

than other planetary than other planetary bodiesbodies AtmosphereAtmosphere OceansOceans Erosion/depositionErosion/deposition

High velocity of impacts High velocity of impacts vaporize the meteorvaporize the meteor

Chesapeake Bay was Chesapeake Bay was created by an impact ~36 created by an impact ~36 million years agomillion years ago Most earthquakes in the Most earthquakes in the

region today are due to region today are due to settling from impact and settling from impact and glacial reboundglacial rebound

Contamination by Contamination by saltwater limits the saltwater limits the freshwater available todayfreshwater available today

Classroom ActivitiesClassroom Activities

• Plate Boundaries– Plot earthquakes on maps– Graph earthquakes based on depth,

magnitude, and boundary type• Earthquakes on convergent boundaries are deeper

and larger– For more advanced students, locate the

epicenter using “Virtual Earthquake”– Plot volcanoes to locate plate boundaries

(convergent) and hot spots (Hawaii)

• Discuss the week’s planetary events in terms of potential human impact