in past episodes we learned that plates are fragments of earth's lithosphere
and there are two different kinds of plates oceanic and continental plates move
independently and interact to shape landscapes and cause earthquakes and volcanic eruptions
can you guess how many different types of movement there can be the answer is three plates can move
towards each other at convergent plate boundaries away from each other at divergent plate boundaries
and slide past each other at transform boundaries plate boundaries have the most
earthquakes and volcanoes in this episode we're going to focus on convergent plate boundaries
a convergent plate boundary is the meeting place of two plates converging which just means moving
towards each other where they meet one of the plates will sink or subduct beneath the other
there are two different types of convergent margins
depending on whether the subducting plate is continental or oceanic
if a continental plate subducts beneath another continental plate
we have a collision tone where continental crust is folded faulted and pushed under the other plate
creating mountain ranges like the himalayans
these mountain ranges are the highest places on planet earth
in contrast where an oceanic plate subducts beneath another continental or oceanic plate
an oceanic trench forms trenches are the deepest places on earth's surface let's talk about the
subduction of oceanic crust first and then we'll talk about continental collision zones there are
three important features of convergent margins that subduct oceanic plates trenches earthquakes
and volcanoes
trenches are where the oceanic plate begins to subduct
the deepest earthquakes in the earth happen beneath convergent margins
these earthquakes define an inclined seismic zone that tells us where the seducted oceanic plate is
a chain of volcanoes is also found above the subduction zone these volcanoes are called an
island arc if they are found in the ocean like the islands of japan the philippines
or indonesia
continental margin volcanoes also make high mountains on land
like the andes of south america
or the cascade volcanoes of oregon and washington
convergent margins subducting oceanic crust are especially important around the pacific ocean
and the many volcanoes associated with these are part of what is called the ring of fire
regions around convergent plate margins can be dangerous because of the strong earthquakes
and violent volcanic eruptions
very powerful earthquakes can happen in the subduction zone
including the 2011 earthquake that struck japan
sometimes these strong earthquakes happen under the ocean and this can cause a devastating tsunami
the second type of convergent boundary is when two continental plates meet causing a continental
collision remember the continental plates are lighter and thicker so it is really hard for
continental plates to sink into the mantle have you ever tried to push a ball water the ball
will rise to the surface and float because it's filled with air which is less dense than water
just like the ball in the swimming pool the lower density continental plates are not
easy to subduct into the mantle instead of going down the continental cross literally bunches up
thickening and folding to create spectacular mountain ranges like the himalayas
or the alps
mount everest is the highest mountain in the world and formed as a result of the collision
between the indian and asian continental plates
these mountain ranges are not only high but are some of the most beautiful places on earth
in the next episode we visit spreading centers and see how plates are born see you next time
when we will talk about divergent plate boundaries
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you