Plate Tectonics Flashcards
Alfred Wegener
German meteorologist and geophysicist was first to advance idea of mobile continents in 1912
Continental drift
Continents are slowly drifting across globe
Paleomagnetism
The study of earths ancient magnetic field
Magnetic dip/inclination
The degree to which a magnetic particle points into earths surface.
Mid-ocean ridge
A continuous underwater mountain range that winds through every ocean basin in the world
Sea floor spreading
New ocean floor is split in two and carried away from the axis, replaced by upwelling of volcanic material that fills the void with new strips of seafloor
Spreading center
The axis of the mid-ocean ridge
Ocean trenches
Deepest parts of ocean floor and resemble a narrow crease
Subduction
Lithospheric plate that bends downward and slowly plunges back into earths interior
Subduction zone
Sloping area from the trench along the downward plate
Heat flow
Heat from earths interior released to the surface
Earthquakes
Sudden releases of energy caused by fault movement or volcanic eruptions
Asthenosphere
Entirely contained within upper mantle
It is a relatively hot plastic (can mold) region below lithosphere so it will flow when gradual force is applied to it
Mesosphere
Beneath asthenosphere
More rigid due to increased pressure at depth
Lithosphere
Relatively cool, rigid shell that includes all of the crust and the topmost part of the mantle
It is brittle
Oceanic crust
Composed of igneous rock, basalt, which is dark colored and has high density of 3.0g/cm^3
Continental crust
Composed of lower density and lighter-colored igneous rock, granite. Has density of around 2.7g/cm^3
Isostatic adjustment
The vertical movement of crust-is the result of buoyancy of earths lithosphere as it floats on the denser, plastic-like asthenosphere below.
Divergent boundaries
Occurs where two plates move apart such as along crest of mid-ocean ridge where sea floor spreading creates new oceanic lithosphere
New seafloor created
Ocean to ocean or continent to continent
Oceanic rises
The gently sloping and fast spreading parts of the mid ocean ridge
Oceanic ridges
Steeper sloping and lower spreading areas of mid-ocean ridge
Convergent boundaries
Where two plates move together and collide-results in destruction of ocean crust as one plate plunged below the other and is ee melted in mantle
Forms deep ocean trenches
Oceanic-continental convergence
Denser ocean plate subducts
Basaltic rock melted and begins to rise to surface through the overriding continental plate.
Basalt rich magma mixes with granite of continental crust and make andesitic volcanic eruptions
Oceanic-oceanic convergence
Denser ocean plate is subducted (usually older because more time to cool) so molten material is mostly granitic and makes volcanoes but basalt has less silica so less viscous so eruptions not as destructive.
Makes deepest ocean trenches
Continental-continental convergence
Tall uplifted mountain range created by collision of two plates
Transform faulting
Movement of one plate past another produces shallow but strong earthquakes in lithosphere.
Always occurs between two segments of mid ocean ridge
Oceanic transform fault and continental transform fault
Mantle plumes
Columnar areas of hot molten rock that arise from deep within mantle
Hotspots
Areas where mantle plumes come to surface
Theory of Plate Tectonics
The outermost portion of earth is composed of a patchwork of thin, rigid plates that movie horizontally with respect to one another
