Plate boundaries Flashcards
What happens at a convergent : continental to continental plate boundary?
A collision margin occurs. As both plates have about the same density, and are less dense than the asthenosphere beneath them, neither plate is actually subducted.
They collide and sediments between them are crumpled and forced up to form high fold mountains
e.g Himalayas
Example of high fold mountains
Himalayas
What happens at convergent: continental to oceanic plate boundaries?
Oceanic plate is denser than the continental plate, so when the plates collide, the oceanic plate slides beneath the continental into the mantle and melts.
Deep ocean trenches mark the place where the oceanic plate starts to sink beneath the continental plate.
Subduction leads to the formation of fold mountains. Since plates constantly move towards each other, those mountains will continue to grow.
What happens at conservative plate boundaries?
Plates slide past each other, forming a conservative plate margin.
This results in a major break in the crust between them as they move.
The break itself is called a fault, on a large scale its called a transform fault which affects a wider area.
Friction causes the earthquake.
What happens at a convergent: Oceanic to oceanic plate boundary
The denser plate is subducted beneath other one.
Deep ocean trenches occur and the subducted plate melts- creating magma.
This rises up from the benioff zone to form underwater volcanoes, rise above sea level to form separate island volcanoes, which are usually found in curved lines called island arcs.
Mid-ocean ridges of underwater mountains extend for how many kilometers?
60,000
How are mid-ocean ridges formed?
Transform faults cut across these ridges as they spread out different routes.
Shallow focus earthquakes occur, but pose little threat to humans because their shakes are minor and occur underwater.
Regular volcanic eruptions also creates submarine volcanoes along these mid-ocean ridges.
Some of which go above sea-level to form islands.
