Download Plates move apart

6.3 Plates move apart
Tectonic plates have different boundaries
The
edge of two plates meet at a plate
boundary.
Divergent Boundary
where plates move apart
Convergent Boundary:
where plate push
together.
Transform Boundary :
occurs where plates scrape
past each other.
Mid Ocean Ridges and Rift Valleys
 As
the sea floor spreads, it creates a gap between
the ridges called Rift Valley.
 Mid-
ocean ridges: the
longest chain of mountains on
Earth.
 Mid-
ocean ridges, rift valleys form along divergent
boundary, as the sea floor spreads apart.
Sea-Floor Rock and Magnetic Reversals
 Magnetic
reversal: when the
north pole becomes south and
the south pole becomes north.
 Patterns
of Magnetic Reversal
recorded in ocean- floor rocks
provide evidence of plate
movement.
Continents splits apart at divergent
boundaries
1- On land the hot material rises in the mantle
causes the crust to bulge upward, then the
crust cracks as it is stretched and the rift valley
forms.
2- As the rift valley grows Wider, continents
begin to split apart.
3- If the rift valley continued to widen
, the thinned valley floor sinks lower
and lower until it is below sea level.
4- The valley will
be flooded by
oceans or rivers
forming a sea
or a lake.
Hot spots can be used to track plate
movements.
A
plume of magma from the
mantle melts the rock in the
plate above it until a volcano
forms.
 They
provide a fixed point
to measure plate movements.
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