Plate Tectonics

A Brief Overview

The Earth’s Plates

http://www.nature.nps.gov/geology/usgsnps/pltec/pltec2.html

Layers of the Earth• Chemical • Physical

http://www.burkemuseum.org/static/geo_history_wa/The%20Restless%20Earth%20v.2.0.htm

Layers of the Earth and Food• Lithosphere

– Chocolate: when it’s cold, it’s hard and breaks, but as it warms up it can bend and eventually melt

• Asthenosphere– Honey: it’s thick and sticky, but it flows

• Mantle– Crumbled cookies: it’s solid but can move and

convect

• Outer core– Milk: liquid

• Inner core– Peach pit: solid

Plate Boundaries

Stern, R. J., Subduction zones, Rev. Geophys., 40(4), 1012, doi:10.1029/2001RG000108, 2002

Margins: Divergent• Mid-Ocean Ridges

– Mid Atlantic Ridge

• Continental Rifts– East African Rift Valley

http://www.phschool.com/atschool/phsciexp/internet_activity/cfd-1014_midocean.html

http://www.talktalk.co.uk/reference/encyclopaedia/hutchinson/m0006339.html

Margins: Convergent

• Ocean-ocean subduction– Island arc: Marianas

http://www.see.leeds.ac.uk/structure/dynamicearth/subduction/cordillera_islandarc.htm

Margins: Convergent

• Ocean-continent subduction– Volcanic arc and mountains: Andes

http://www.see.leeds.ac.uk/structure/dynamicearth/subduction/cordillera_islandarc.htm

Margins: Convergent

• Continent-continent collision– Large mountain range: Himalayas and Alps

http://www.unil.ch/igp/page23575_en.html

Margins: Transform• Marine

– Transform faults: • Mid Atlantic Ridge

• Terrestrial– Strike-slip faults:

• San Andreas Fault

http://geomaps.wr.usgs.gov/archive/socal/geology/inland_empire/socal_faults.html

Evidence for Plate Tectonics• Fit of the continents• Sea floor ages and magnetic anomalies –

evidence of ocean spreading• Paleontology – similar species on now widely

separated continents• Seismicity and volcanism concentrated at

plate boundaries – evidence of oceanic subduction

• Hot spot tracks – record movement of plates over “fixed” hot spot

• GPS