1ST QUARTER LESSON OF GRADE 10 SCIENCE

1. DIVERGENT
PLATE
BOUNDARY
By:
Daryl F. Cadanilla

2. PLATE BOUNDARIES
Determining location of earthquake epicenters
plays a vital role in laying the foundation of
plate tectonics.
The places on Earth where most of the
earthquakes originated or some of the
mountains and volcanoes were formed
marked the boundaries of each lithospheric
plates

3. 3 TYPESOF PLATE BOUNDARIES
 DIVERGENT PLATE BOUNDARY
 2 lithospheric plates move away from
each other
 CONVERGENT PLATE BOUNDARY
 2 lithospheric plates move toward
each other
 TRANSFROM FAULT
2 lithospheric plates slide past each other

4. DIVERGENT BOUNDARY
Objectives:
--Explain the processes that
occur along divergent
boundaries.
--Determine the results of
plates that are moving apart

5. Analyze the
photographs of rift
valleys and oceanic
ridges and answer
the question that
follows.

10. Questions:
 1. What are common in four
pictures?
 2.Million of years ago, landmasses
in each picture were once connected
.What do you think is happening to
the Earth’s crust in those pictures?
 3. If this event continues for million
of years, what do you think will be
the effect on the crust?

11. Short video

12. Types of divergent plate boundary
 1. continental divergence
-As the two plates pull apart, normal faults develop on
both sides of the rift, and the central blocks slide
downwards
Early in the rift-forming process, streams and rivers
will flow into the sinking rift valley to form a long
linear lake.
As the rift grows deeper it might drop below sea level,
allowing ocean waters to flow in.This will produce a
narrow, shallow sea within the rift.
This rift can then grow deeper and wider. If rifting
continues, a new ocean basin could be produced.

15. Example
 The East Africa RiftValley is a classic example of
this type of plate boundary.The East Africa Rift is
in a very early stage of development.The plate
has not been completely rifted, and the rift valley
is still above sea level but occupied by lakes at
several locations.The Red Sea is an example of a
more completely developed rift.There the plates
have fully separated, and the central rift valley
has dropped below sea level.

16. GEOLOGICAL EFFECTS
 a rift valley sometimes occupied by long
linear lakes or a shallow arm of the
ocean; numerous normal faults
bounding a central rift valley;
 shallow earthquake activity along the
normal faults.
 Volcanic activity sometimes occurs
within the rift.

17. 2. Oceanic Divergence
 When a divergent boundary occurs beneath
oceanic lithosphere, the rising convection
current below lifts the lithosphere, producing a
mid-ocean ridge.
 Extensional forces stretch the lithosphere and
produce a deep fissure. When the fissure opens,
pressure is reduced on the super-heated mantle
material below.
 It responds by melting, and the new magma
flows into the fissure.The magma then solidifies
and the process repeats itself.

20. example
 The Mid-Atlantic Ridge is a classic example of
this type of plate boundary.The Ridge is a
high area compared to the surrounding
seafloor because of the lift from the
convection current below.

21. GEOLOGICAL EFFECTS
 a submarine mountain range such as the Mid-
Atlantic Ridge;
 volcanic activity in the form of fissure
eruptions;
 shallow earthquake activity;
 creation of new seafloor and a widening
ocean basin.

23. ASSESSMENT
 Which of the following is NOT an example
of a divergent plate boundary?
a.The boundary between the Nazca Plate and
the South American Plate
b.The boundary between the North American
Plate and the Eurasian Plate
c.The East African Rift
d.The plate boundary that passes over Iceland

24. Which of the following describes a divergent
boundary?
a. When two plates collide with each other
b. When two plates interact in any way
c.When two plates move apart from each other
d.When two plates slide alongside each other

25. What feature forms near divergent
boundaries between two pieces of oceanic
crust?
a. Mid-ocean ridge
b. Non-volcanic mountain
c. Continental rift valley
d.Trench