this presentation talks about the three types of plate boundaries and their results also.

1. Plate Boundaries
Mr. Yonas Gemeda
September 2019
Addis Ababa

2.  Plate boundary is the place where two plates
meet.
 What does plate mean?
 Tectonic plate is a piece of lithosphere that
moves slowly on asthenosphere.
 Seven major, eight minor and numerous micro
plates have been identified.
Definition

3.  Lithosphere is the outer and rigid layer of the
earth, comprising the crust and the upper part
of the mantle.
 Plates can be continental, oceanic or a mixture
of both.
What does lithosphere
mean?

4.  There are three types of plate boundary
1. Constructive (divergent)
2. Destructive (convergent)
3. conservative
Types of plate boundaries

5.  If two continental plates move away from each
other, a rift valley may form as the central
block of land drops down between the faults.
Eg: east African Rift Valley
Constructive (divergent)

6.  If two oceanic plates pulling away from each
other, a gap or weakness is formed and magma
from the mantle rises to the surface because of
convection currents. The magma turns to lava
and form new basaltic ocean crust. The whole
process is called sea floor spreading or ridge
push.
Ocean to ocean

7. Destructive (converging )

8.  A destructive plate boundary can be
found between a continental plate and
oceanic plate, between two oceanic plates
and between two continental plates.
Cont’d

9.  At a destructive plate boundary an oceanic
plate and continental plate move towards each
other because of convection currents in the
mantle. The denser oceanic plate is forced
down, or sub ducted, under the lighter
continental plate. This process is called
subduction or slab pull and it takes place in
subduction zone.
Cont’d

10.  When two oceanic plates move towards each
other, the older and denser plate is subducted.
The magma rises upward and erupt at the
surface forms a chain of volcanic islands called
island arc.
 If two continental plates move towards each
other, this is called collision zone. The
sediments between the two plates are squeezed
together and pushed upwards to form fold
mountains.
Cont’d

11. Conservative (transform)

12.  At conservative plate boundary, no plate is
being destroyed or created.
 The plates are sliding each other .
Cont’d

13. Thank you
!!! !!!
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