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8.9AB Plate Tectonic Theory Picture Vocabulary © 2011 Rice University – All Rights Reserved Plate Tectonic Theory Theory that the lithosphere is divided into tectonic plates that slowly move on top of the asthenosphere © 2011 Rice University – All Rights Reserved Lithosphere Cool, rigid, outermost layer of Earth that is divided into enormous pieces called tectonic plates; consists of the crust and the rigid uppermost part of the mantle © 2011 Rice University – All Rights Reserved Continental Drift The theory that continents were once connected but have drifted apart © 2011 Rice University – All Rights Reserved Fossil Evidence Significant climate change indicated by fossils found in Antarctica and suggest the continent was once much closer to the equator Impressions of organisms left in rock layers that indicate the organisms once lived in the area © 2011 Rice University – All Rights Reserved Sea Floor Spreading Evidence Reversed polarity Normal polarity A parallel pattern of rock material found at identical locations on each side of the Mid-Atlantic Ridge reveals rock of the same geologic age and polarity © 2011 Rice University – All Rights Reserved Divergent Boundary Great Rift Valley of Africa Mid-Ocean Ridge The boundary between two tectonic plates moving away from each other; on land creates rift valleys, on the sea floor creates new ocean crust © 2011 Rice University – All Rights Reserved Convergent Boundary with Subduction Volcanic mountain range Some oceanic crust melts and forces its way upward The boundary between two tectonic plates moving toward each other resulting in volcanic activity when a denser ocean plate subducts below continental plate © 2011 Rice University – All Rights Reserved Subduction Subduction Zone Note the formation of a trench within the Subduction Zone A plate is forced below when one plate is denser than another as they converge; occurs at continental to oceanic boundaries and oceanic to oceanic boundaries © 2011 Rice University – All Rights Reserved Convergent Boundary with Mountain Building Continental plate Crust Continental plate Crust Lithosphere Asthenosphere A major geological event; occurs when continental plates of equal density converge © 2011 Rice University – All Rights Reserved Transform Boundary © 2011 The boundary between two plates that slide pass one another, sudden shifts result in major geological events such as earthquakes and the release of stored energy Rice University – All Rights Reserved
