Types of Plate Boundaries Flashcards
what is another name for plate boundary?
plate margin
What are the three main types of plate margins?
divergent, convergent, transform
What are the sub-types of the divergent plate margins?
oceanic, continental
What are the sub-types of convergent plate margins?
ocean-continent, continent-continent, ocean-ocean
What are the two types of crust on the Earth?
continental and oceanic
What are the general features of the continetal crust?
- older
- more felsic (Si-rich) rocks -
less dense (avg. 2.7 gm/cm^3 - thicker (avg. 35 km; up to 65km)
What are the general features of the oceanic crust?
- younger
- more mafic (Si-poor) rocks
- more dense
- thinner (avg. 5 km)
Which crust, oceanic or continental, is older?
continental
which crust, oceanic or continental, is thicker?
continental
which crust, oceanic or continental as high mafic rock content?
oceanic
When does the importance of crust-type come into play?
when the two types of crust interact at plate boundaries
A _______ boundary is a boundary between two plates that are moving apart from one another
divergent
Since plates are moving apart at divergent boundaries it results in ______ and ______ earthquakes
shallow, weak
what kind of earthquakes happen at divergent boundaries?
shallop and weak earthquakes
what is a divergent plate boundary?
when two plates are moving apart from one another
What are the two types of divergent margins?
oceanic, and continental
the two types of divergent margins are based on…
the types of crust that are interacting
Where do we commonly see oceanic divergent margins?
at mid-ocean ridges
What is a good example of a continental divergent margin?
African Rift Valley
What is a good example of a divergent margin?
Iceland, located on top of the mid-ocean ridge on the Atlantic Ocean. Iceland is actually composed of oceanic crust. it is just a big island that sprouted up from the bottom of the ocean
When two plates move towards each other it is called a ________ margin
convergent
Whenever two plates are moving towards eachother one of the plates _____ down under the under plate
sinks
The plate that sinks down is the _______ plate
subducting
At the ______ zone we see a deep trench form
subduction
What do we see at the subduction zone?
a deep trench form
The subduction zone creates deep _____ and _______ mountain chains
trenches, volcanic
The plate that subducts depends on what type of _____ it is made up of
crust
When oceanic crust collides with another oceanic crust one plate dips down below and starts to _____
melt
As the subjecting plate of an ocean-ocean convergence melts the _____ bubbles up to to the surface and creates _____ of volcanoes
magma, islands
- linear volcanic islands form along the boundary
In ocean-continent divergent margins, which crust sinks below the other?
oceanic
Why does the oceanic crust sink below the continental?
because it is more dense
As the ______ crust sinks it begins to melt, and the magma bubbles up through the ______ crust and creates _____ mountain chains along the coast.
oceanic, continental, volcanic
What forms at the continent-continent divergent zone?
mountain ranges
What is an example of a continent-continent divergent zone?
the Himalayas - where India is colliding into the rest of Asia
Earthquakes are convergent margins are _____ and _____
deep, powerful
what kind of earthquakes happen at convergent margins?
deep and powerful earthquakes
Why are earthquakes at convergent margins deep and powerful?
one plate descends below another and the plates interact at vary deep depths, and because the plates are moving towards each other you can have very violent and powerful earthquakes
Earthquakes get ______ the further from the boundary you move on the ______ plate
deeper, overriding
A ______ margin’s plates are sliding past one another
transform
What is an example of a transform margin?
the San Andreas fault
Earthquakes at transform margins are…
shallow, moderately powerful, and frequent
