Transcript Slide 1
Plate Tectonics Brigitte Steinmetz John Adams Middle School Disclaimer The images, maps and diagrams in this presentation were taken from the public domain on the world wide web. Permissions were granted where possible. Any privately owned images not available for this non-commercial, educational project will gladly be removed. E-mail: [email protected] Earth’s Interior Oceanic Crust Oceanic B. Crust C. Asthenosphere A. Continental Crust Lithosphere D. E. Mantle Outer Core Inner Core The Mantle • Upper part = hot & rigid (hard) – part of the lithosphere. • Middle part = hotter & soft (asthenosphere) • Lower part = hottest & solid http://pubs.usgs.gov/publications/text/inside.html - 12/7/2004 The Earth is HOT • Review Heat Transfer – Radiation = • Energy transferred through an empty space (i.e. sun energy). – Conduction = • Energy transferred directly from one object to another (i.e. burning feet at the beach). – Convection = • Energy transferred through the movement of a heated fluid. Convection inside Earth http://pubs.usgs.gov/publications/text/unanswered.html - 12/7/2004 Convection inside Earth • Convection in the mantle causes the crust’s plates to move! http://www2.nature.nps.gov/geology/usgsnps/animate/A08.gif - 12/7/2004 Continental Drift • Alfred Wegener: – Hypothesis: • About 300 MYA all continents were once joined together forming a SUPER continent! – He named it PANGEA! • Pangaea begins to break apart and continents move to present day locations • Occured tens of millions of years ago http://www.mpm.edu/reef/pt-gif.html - 12/7/2004 Continental Drift Theory Evidence of Drift • Continents fit together like a puzzle • Land forms similar on different continents (like mountain ranges) Evidence of Drift Continued • Fossils found in unlikely places – For example: • Reptiles were found in Antarctica. • Tropical plants found in ice covered places. http://www.soc.soton.ac.uk/CHD/classroom@sea/carlsberg/images/f ossil_correlation_lge.jpg - November 27, 2005. What about the FUTURE? Plates on the Move • Plates move 1-10cm/year. • Moving apart. • Moving plates cause: –Earthquakes –Volcanoes http://pubs.usgs.gov/publications/text/Krafla.html - December 13, 2004. Plate Boundaries • Place where two plates meet and interact. • Three Types: –Transform –Divergent –Convergent http://pubs.usgs.gov/publications/text/ridge.html - December 13, 2004. Convergent Boundaries • Occurs when two plates collide (run into each other). • Two types: Continental Oceanic http://pubs.usgs.gov/publications/text/understanding.html - December 13, 2004. Continental Convergence • Two plates collide and buckle upwards forming mountains and cause earthquakes! Oceanic Convergence • When two plates collide, one goes under the other called subduction! • Causes volcanoes. Divergent Plate Boundaries • When two plates move apart. • Occurs at two places: Mid-Oceanic Ridge Land – Rift Valley http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0006339.html - December 13, 2004 Sea Floor Spreading • Magma comes up forming new rock and pushes old rock to sides. http://www.uwsp.edu/geo/faculty/ritter/glossary/S_U/sea_flr_spread.html - December 13, 2004. Which Rock is Older? • The older rock is closer to the continents. • New rock is at the mid-oceanic ridge. http://www.soc.soton.ac.uk/CHD/classroom@sea/carlsberg/sci ence/oceanic_constr.html - December 13, 2004. Where are Mid-Ocean Ridges? Pacific vs. Atlantic Oceans Pacific Ocean is getting smaller – continents are coming together. Oceanic crust is moving under them. Atlantic Ocean is getting bigger – USA and Europe are moving apart! http://www.soc.soton.ac.uk/CHD/classroom@sea/carlsberg/science/oceanic_constr.html - December 13, 2004. Transform Boundary • Plates slide past each other in opposite directions. • Causes a lot of earthquakes.