Tectonics Lesson 4: Convergent Plate Boundaries Flashcards
Define subduction zone
Broad areas where two plates are moving together. Often the thinner, more dense oceanic plate descends beneath the continental plate.
Define locked fault
In a subduction zone, as plates move together they can get stuck due to frictional resistance. Such faults may store strain for extended periods of time, which is eventually released in a large magnitude earthquake
Define benioff zone
An area of seismicity corresponding with the slab being thrust downwards in a subduction zone
What are the 3 types of convergent plate boundaries?
Oceanic vs oceanic
Oceanic vs continental
Continental vs continental
Oceanic vs continental boundaries
Oceanic crust is more dense than continental crust, so the oceanic crust subducts beneath the continental crust when they collide. This forms deep ocean trenches
The continental plate is folded and slowly pushed up forming fold mountains.
What are earthquakes like along oceanic vs. continental?
Friction between colliding plates causes intermediate and deep earthquakes in the Benioff zone.
These earthquakes are some of the largest and most damaging.
What are volcanoes like along oceanic vs. continental?
Explosive volcanoes generated as magma created form the melting oceanic plate pushes up through the fault in the continental lithosphere to reach the surface.
Less frequent, but more destructive
Example of where convergent plate boundaries are found?
Pacific Ring of Fire
Oceanic vs oceanic plate boundaries?
The denser of faster of the two plates is subducted beneath the other, forming deep ocean trenches at the point of subduction.
What type of earthquakes form at oceanic vs oceanic?
Shallow-deep earthquakes
Some of the most powerful due to being close to the surface and less energy being dissipated through the Earth
What type volcanoes form at oceanic vs oceanic?
Underwater/ submarine volcanoes when magma rises from the melted subducted plate. These can grow above sea level over millions of years, forming separate island volcanoes called island arcs.
What forms when two continental plates meet?
Collison margin
Continental vs continental plate boundaries
Both plates have the same density, and are less dense than the asthenosphere beneath them, so neither plate is subducted.
They collide and sediment between them is crumpled and forced up to form high fold mountains.
Example of continental vs continental
Himalayas
When is there subduction at continental vs continental?
Compressed and denser sediments result in plate subduction beneath them
