convergent/ destructive plate margin Flashcards
what is a convergent/destructive plate margin
In plate tectonics, a convergent boundary, also known as a destructive plate boundary (because of subduction), is an actively deforming region where two (or more) tectonic plates or fragments of the lithosphere move toward one another and collide.
what happens at convergent margins
As a result of pressure, friction, and plate material melting in the mantle, earthquakes and volcanoes are common near convergent boundaries.
types of plate margin
continental-oceanic margin
oceanic - oceanic
continental to continental
what is subduction
where one plate goes beneath another
what is uplift
where plates collide head on causing uplift creating mountain ranges
example of subduction
nazca - south american plate
example of uplift
himalayas
how do earthquakes happen
at faults (margin boundary) where stored energy is released when moved
sideways movement of plate?
conservative margin (susceptable to transform faulting)
how do earthquakes occur on faults?
fault movement releases energy**
what is a hot spot?
volcano within a plate, which is the surface expression of a mantle plume
what is an island arc
islands created by volcanic activity from hot spot.
what is an volcanic arc
occur on
example of island arc
hawaii/mariana islands
example of volcanic arc
andean volcanic belt
why does oceanic plate go under continental?
beause it is heavier (igneous rocks basalt, gabbro, dolorite)
why is there volcanic activity at construuctive margins
because the oceanic crust melts under the continental crust. melts due to heat from friction and being closer to the core. turns to magma, supplying volcanoes
where do island arcs occur
O-O margins
where do volcanic arcs occur?
O-C margins
where does uplift occur?
C-C margins
deep ocean trench
marianas trench (west pacific) (deepest trench)
convergent margins create earthquakes by…
..friction
super continent , africa and south america
godwanaland
technique to construct a 3D image of heat flow within the earth
siesmic tomography
earthquakes in convergent margins DEPTH
shallow-deep
0-700km
earthquakes in convergent margins MAGNITUDE
high magnitutde
earthquakes in convergent margins FREQUENCY
low frequency
earthquakes in divergent margins DEPTH
shallow
0-70km
earthquakes in divergent margins MAGNITUDE
low magnitude
earthquakes in divergent margins FREQUENCY
high frequency
HOT SPOT?
formed from MANTLE PLUME, fixed in place, creates volcanic/island arc.
Mantle plume
stationary area of high heat fllow in the mantle, produces magma that that feeds hot spot volcanoes
