The document discusses theories of the Earth's movement including continental drift and seafloor spreading. It explains that mantle convection causes lithospheric plates to move via convection currents. Hot mantle material rises and cools, sinking elsewhere, moving the plates over geologic timescales through processes like ridge push and slab pull. Plate tectonics integrates these ideas to explain volcanoes, earthquakes, and mountain building at plate boundaries.

1. EARTH’S MECHANISM

2. THEORIES OF THE
EARTH’S MOVEMENT

3. 1. The Continental
Drift

4. In 1912, Alfred Wegener (pronounced as vey-guh-
nuh r), a German meteorologist, proposed a theory
that about 200 million years ago, the continents
were once one large landmass.
He called this landmass Pangaea, a Greek word
which means “All Earth.”

5. This Pangaea started to
break into two smaller
supercontinent called
Laurasia and
Gondwanaland during
the Jurassic Period.
These smaller
supercontinents broke
into the continents and
these continents
separated and drifted
apart since then.

7. SEAFLOOR SPREADING

8. The Seafloor Spreading Theory
According to this theory, hot, less dense
material from below the earth’s crust rises
towards the surface at the mid-ocean ridge.
This material flows sideways carrying the
seafloor away from the ridge, and creates a
crack in the crust. The magma flows out of
the crack, cools down and becomes the new
seafloor.

9. The Earth’s whole lithosphere is broken
into several rigid sections called plates
that move constantly.

10. GUESS THE WORD

11. tmnael
• a layer beneath where the
less dense hot molten
material rises and sinks

12. thprehaeosens
a soft, weak and plastic-like layer,
upper part of the mantle where
lithospheric plates float and move.

13. mmgaa
hot molten rocks formed beneath the Earth’s surface.

14. noitcevnoc
ctunrre
facilitates the movement
of the lithospheric plates

15. orce
innermost layer of the
earth which generates heat
to the mantle

16. Plate Tectonic Theory
• Plate tectonic Theory was developed in 1960s, stating
that the Earth’s lithosphere-the crust and the upper
mantle- is broken up into a several pieces called plates
that move slowly.

17. It explains how the
massive plates move
along the different types
of plate tectonic
boundaries (convergent,
divergent and transform
fault) where they interact,
and the geologic events
(earthquakes and
subduction) and geologic
features (formation of
mountains, volcanoes
and trenches) that occur
at their boundaries.

18. What Makes Lithospheric
Plates Move?

19. HEAT
TRANSFER

21. •A convection current
is a heat transfer
process that involves
the movement of
energy from one
place to another.

22. The convection currents tend to move a fluid, gas particles,
or molten rock. These are due to the differences in the
densities and the temperature of a specific gas or a fluid.
Due to this temperature difference, the hot fluid tends to
rise as it expands, whereas cold fluid tends to sink
because it contracts.

23. Convection current also happens in the
mantle. The mantle is the second
inner layer of Earth, made up of mostly
hot rocks and magma.
It is a very hot layer because of the heat
generated by the core. The source of
heat from the core is due to the decay
or breakdown of radioactive elements.
Mantle convection is a process by
which a thermal convection occurs in
the inner layer of the earth.
The differences of the temperature at
the Earth’s interior and surface cause
convection currents to occur within the
mantle.

24. Lithospheric plates are the
parts of the uppermost
layer of the Earth and
they are flowing in an area
called asthenosphere.
Asthenosphere is a soft,
less rigid upper part of the
mantle where the
lithospheric plates float
and move with around.

25. Plates move slowly and constantly when the hot less
dense material rises. The rising hot material cools down in
a certain area so it becomes denser than the cool dense
material sinks, that creates convection cell, with hot rising
currents and cool sinking currents are regularly repeated
and become a cycle.

26. The movement of lithospheric plate is
attributed to mantle convection and
considered as one of the driving
mechanisms for plate motion.
Lithosphere at divergent boundary will uplift
and tear apart due to the rising of hot
magma. The sinking of magma pulls down
the tectonic plate at convergent boundary.
Aside from mantle convection, ridge push,
sliding, and slab pull are other forces that
move the lithospheric plates.

27. •In the process of slab pull, the
presence of a heavier subducting plate
pulls down the trailing slab into the
subduction zone.
• In a ridge push or gravitational sliding process,
the old oceanic crust becomes heavier than the
new oceanic crust and sinks because of the
weight of the raised ridge which pushes down
the older oceanic crust towards the trench at the
subduction zone.

29. LET’S ASSESS!
1. What are the theories that explain plate
movement?
2. What are the three types of heat transfer?
3. How does convection current or mantle
convection work?
4. What are the mechanisms that cause the
lithospheric plate to move?

30. • Arrange the following events in the mantle
convection process. Use numbers 1-5.
____a. Lithospheric plates move in the
asthenosphere due to rising and sinking of
materials.
____b. The decomposition of radioactive elements
causes heat in the interior part of the Earth.
____c. Heat slowly rises to the mantle and creates
convection current.
____d. Heat moves to the core.
____e. The process repeats as cycle.