1.4 plate tectonics Flashcards
what happens at divergent plate boundaries?
when two oceanic plates move apart
what happens during oceanic-oceanic divergent plate boundaries. give an example.
The oceanic plates move apart
The decrease in overlying pressure causes parts of the underlying mantle to melt, forming magma.
Magma rises through the weak areas in the crust to the Earth’s surface, and fills gaps caused by the spreading plates.
Lava cools and solidifies to form basaltic rocks.
The rocks make up a new oceanic crust.
The mid-ocean ridge forms.
E.g. North American plate and oceanic eurasian plate move apart - Mid-Atlantic ridge.
what happens during continental-continental divergent plate boundaries and give an example.
two continental plates move apart
Rocks fracture to form parallel faults
Rocks between these faults collapses, forming rift valley
As the plates move apart, the decrease in overlying pressure causes parts of the underlying mantle to melt.
magma rises through weak areas forming rift volcanoes.
Earthquake occurs.
e.g. Nubian plates pull apart from the Somalian plate, forming East African Rift Valley.
what happens at convergent plate boundaries?
tectonic plates moving towards each other.
what happens during oceanic-oceanic convergent plate boundaries? Give an example.
When two oceanic crusts collide, the denser oceanic crusts subducts beneath the less dense crust.
This forms a deep depression known as oceanic trench
The sinking crust will melt under intense pressure and heat from the mantle to become magma.
This results in the formation of oceanic trench.
e.g. pacific plate and philippine plate moving towards each other forming mariana trench.
what happens during continental-continental convergent plate boundary. Give an example.
When two continental crusts of similar densities converge, massive buckling and folding of the crust takes place to form a fold mountain range.
e.g. Indo-Australian plate and Eurasian plate forming the himalayan range
what is folding?
when plates move towards each other and collide, the resultant compressional forces causes layers of rock to buckle and fold. This compression is known as folding.
what happens during oceanic-continental convergent plate boundary? Give an example.
Both oceanic and continental plates move towards each other.
The denser oceanic plate subducts beneath the continental plate .
This forms an oceanic trench in subduction zone.
As the subduction plate sinks into the mantle, the high pressure forces water out of its oceanic crust.
Water lowers the melting point of the overlying mantle, causing it to melt, forming magma.
Magma rises through weak areas in the crust to the Earth’s surface, forming undersea volcanoes on the continental plate.
Enormous pressure at this plate boundary causes rock on the continental plate to be uplifted and buckled, forming fold mountains.
e.g. oceanic Nazca plate converges with the continental South American plate (Peru-Chile trench)
what happens at transform plate boundaries?
tectonic plates slides past each other
no crust is created or destroyed
what happens at transform plate boundaries? Give an example.
A transform boundary is formed when two plates slide each other.
This movement results in the formation of a transform fault.
In the process, tremendous stress builds up and is eventually released often in the form of violent earthquakes.
e.g. Pacific plate sliding past North American plate (San Andreas Fault)
