Lecture on Plate Tectonics www.AssignmentPoint.com

Plate Tectonics Can Explain: 1. The matching coastlines of Africa and Europe with South America and North America. 2. The presence of midocean ridges. 3. Volcanic mountain chains around the Pacific Ocean basin.

Plate tectonics can explain matching coastlines of South America and Africa, as well as matching geology for older rock units on the two continents.

Paleontological evidence supports plate tectonics and plate motions.

Geothermal activity (shown as light color) most often occurs near tectonic plate boundaries and is less common in the interior of continents. There are some locations around the world where geothermal activity occurs in the interior of continents, but these occurrences can be explained in tectonic context.

To understand plate tectonics one must understand the dynamics between the solid, rigid lithosphere that is floating on a partially molten asthenospherse. The lithosphere is composed of continental and ocean crust and the uppermost solid mantle. The asthenosphere is composed of the upper mantle and is at or near the melting temperature for upper mantle rock.

Inclination of the earth’s magnetic field varies over latitude Inclination of the earth’s magnetic field varies over latitude. It is parallel to the surface over the equator and vertical over the magnetic poles.

Ocean-Ocean lithosphere convergence (subduction). Examples: Japan and Phillipines Ocean-Continent lithosphere convergence (subduction). Examples: Andes Mountains and Cascade Mountains. Continent-Continent lithosphere collision (no subduction). Examples: Himalaya Mountains and European Alps.

Columbia Plateau Cascades Puget Lowland Olympic or Coastal Mts. Structure of a subduction zone. Note that the geographic features relevant to the Cascadia subduction zone are noted in red.

Ocean-Continental Convergence and formation of a continental volcanic arc.

Mt. Rainier, Washington. Andesitic volcano.

Continental collisions are preceded by ocean-continental convergence. As the continental lithosphere arrives at the subduction zone, it cannot be subducted because of its low density. The “collision” cause upwarping and deformation of the ocean floor and ocean lithosphere. Even segments of the upper mantle can be squeezed to the surface along the suture zone (where the two continents are stitched together).

Uplift of the Himalaya Mountains was the result of collisional tectonics between the Indian and Eurasian Plates.

Formation of Appalachian Mountains resulted from the collision of the African and European Plates with North American Plate prior to 300 million years ago.

Ural Mountains Formation of the Ural Mountains related to collision tectonics prior to 300 Ma ago.

Translational motion of the San Andreas Fault can be seen by offset of streams that cross the fault zone.

Future plate motions are predictable based on current plate motions.

Inclination of the earth’s magnetic field varies over latitude Inclination of the earth’s magnetic field varies over latitude. It is parallel to the surface over the equator and vertical over the magnetic poles.

Movement of tectonic plates (including relative movement of continents can explain the apparent wandering of the paleomagnetic pole over geologic time. Without a context of plate motions, paleomagnetic evidence preserved in the rock record would require unique magnetic poles for different aged rock and locations.