Day 4: Intro to Plate Tectonics Earth Model Day 4: Intro to Plate Tectonics Powerpoint for day 4 of Earth Model activity. Plate Tectonics. Image shows some of the plate boundaries and resulting geologic process such as volcanoes. Image source: http://www.mun.ca/biology/scarr/139411_Plate_Tectonics_(b).jpg

What is continental drift? Millions of years ago there was one supercontinent (one giant landmass) called Pangaea. The theory that the seven modern continents split apart one or more times from a single landmass was suggested by a German scientists, Alfred Wegner. This theory is called Continental Drift: Theory that the continents were at one or more times a single landmass that broke apart and eventually moved into the positions they are today. The link in the bottom left hand corner takes you to a nice Flash animation showing how the continents have split apart. Image source: http://newpangaea.eu/sitebuildercontent/sitebuilderpictures/Pangaea.JPG Animation link

Matching fossils, mountains, rock deposits… In addition to the continents fitting together like a jigsaw puzzle, scientists found matching fossils, mountains, and rock deposits on adjacent continents. This evidence further supported the theory of continental drift. Image source: http://www.jazclass.aust.com/blog/files/drift.gif

Plate Boundaries The Earth’s crust is broken into multiple plates. This image shows all of the plates. The red arrows indicate the direction the plates are moving relative to each other. Click on the next slide and another image will fade in that shows the different types of boundaries. Plate Boundaries: Divergent Boundary: Place where two plates pull apart. Convergent Boundary: Place where two plates come together. Transform Boundary: Place where two plates slide past each other. Image source: http://geology.com/plate-tectonics.jpg

Seafloor Spreading and Subduction Movie Source: http://education.sdsc.edu/optiputer/flash/convection.htm This movie shows the process of convection in the mantle which drives crustal plate movement. The movie will play when it is clicked. You can set the movie to loop if desired. Things to point out: Where the hot material is rising to the crust seafloor spreading is occurring. Point out how you can trace the age of the new crust which is being created by seafloor spreading. This process forms long mountain chains underwater called Mid-Ocean Ridges. As the crust ages and moves away from the spreading axis it eventually gets subducted under another plate. This process creates deep canyons called trenches. This is why there is not any oceanic crust older than 160 million years. Where the plate is being subducted, it eventually gets melted and rises up through the overriding crust to form volcanoes.

Hot Spots Movie source: http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm Hot Spot is a portion of the Earth’s surface that may be far from tectonic boundaries and that experience volcanism due to a rising mantle source. The animation above shows how a plume originating from below the lithosphere, rises upwards through the crust to form a volcano or seamount. The rising mantle source stays relatively stationary as the overriding plate moves. This results in “chains” of volcanoes being formed from hot spots.