Powerpoint Presentation about Plate Tectonics

1. Unit 1: PLATE TECTONICS

2. Index
1. The Internal Structure of the Earth
2. The Movement of Continents
3. The theory of Plate Tectonics
4. The ocean
5. The Mechanisms behind Plate Tectonics

3. 1.1 Earth internal layers
Types of classification
Compositional layers (depending on the
composition)
• CRUST
•Oceanic (10 km, basalt, denser)
• Continental (70 km, Si, less dense)
•MANTLE  peridotite
• CORE  Fe + Ni
Physical layers (depending on the physical state)
• LITHOSPHERE rigid
• LOW VELOCITY ZONE (in the past ASTHENOSPHERE)  ductile and
partially molten
• LOWER MANTLE or MESOSPHERE solid
• CORE
•Outer  molten
• Inner  solid

4. Low velocity zone

6. Page 9: In pairs, analyse the graph and explain your answer
 Temperature increases with depth
 Pressure increases with depht The melting point increases
(the temperature is below the melting point,
It does not reach the melting point
As long as the temperature (green line) is below the melting point
(red line)  SOLID

7. 1.2 Seismic discontinuities
Methods for
studying the
interior of the
Earth
drilling meteorites
study of seismic
waves

8. Kola Peninsula Hole Control Centre

9. Types of seismic waves
P: Primary waves
•The fastest
•through SOLIDS and LIQUIDS
S: Secondary waves
•Slower
•Only through SOLIDS
R and L
• On the surface

11. SEISMOGRAPH (sismómetro o sismógrafo) = device used for
detecting and recording seismic waves.
It draws a seismogram (sismograma)
seismograph seismogram

12. Seismic Network Operations in Toledo (Spain)

13. Imagine you are a scientific and obtain this graph. How would you interpret the
behaviour of the seismic waves?
Primary wave
= Secondary wave

15. The speed of waves changes very obviously in specific places:
SEISMIC DISCONTINUITY = boundary between different internal layers where there is
A change in the speed of the internal seismic waves.
Mohorovicic discontinuity  between the crust and the mantle
 CONTINENTS: 30-40 Km depth
 OCEANS: 10 km depth
Gutenberg discontinuity  between the mantle and the core: 2900 km depth
Why do S-waves dissapear here?!? Because they cannot travel through LIQUIDS
Lehman discontinuity  between outer and inner core
The speed of P-waves increases after Lehman discontinuity
because…
The inner core is SOLID
Activities 1, 2 and 3 page 11

16. Theory of continental drift (1912, Wegener)
(teoría de la deriva continental)
Alfred Wegener

17. Theory of continental drift (1912, Wegener)
 200 million years ago all the continents were joined
together as one, called PANGEA
 Continents have separated, sliding over a continous
layer

18. “650millionYearsIn80seconds” video:
http://www.youtube.com/watch?v=VrBPB1dHYaw&feature=related

19. Evidence of the
theory of
Continental Drift
Paleolithic
evidence: identical
fossils in continents
far apart
Biological
evidence: identical
or similar living
beings in continents
far apart
Geological evidence:
continents fit together
along their coastlines
and have similar rocks
Paleoclimatic
evidence: glaciar
rests appear in
places where now
the climate is
warmer
Paleolithic evidence

20. Rhea (South America)
Ostrich (Africa)
Emu
(Australia)
Biological evidence

21. Geological evidence

22. Paleoclimatic evidence
Activities 7 and 8 page 11

23. 3.1 Seismic and volcanic belts
Earthquakes and volcanoes are located in narrow bands, called seismic belts. They
coincide with the plate boundaries.

24. 3.2 Lithospheric plates
Lithospheric or tectonic plates are fragments of the lithosphere.
Types:
Oceanic  Nazca Plate
Continental  Arabian Plate
Mixed  African Plate

25. 3.3 Types of plate boundaries
http://www.juntadeandalucia.es/averroes/manuales/tectonica_anima
da/tect_swf_files/01[1].swf
 Divergent boundaries (constructive) .
New ocean lithosphere is created
Pillow lavas
Volcanoes + earthquakes

26.  Convergent boundaries (destructive) .
A) Two OCEANIC PLATES collide
Volcanoes + earthquakes
One of the plates slides down the other (subduction),
forming an oceanic trench and an arch of volcanic
islands.
Example: Japan

27. Mariana Islands
and Mariana Trench
The Pacific Plate subducts forming the Mariana Islands and Philippines
Japan

28. B) One CONTINENTAL and one OCEANIC PLATE collide .
Volcanoes + earthquakes
The oceanic plate, which is denser, subducts under
the continental plate forming an oceanic trench and
a mountain range.
Example: Andes

29. B) TWO CONTINENTAL PLATES collide
Earthquakes
None of the plates subducts. A mountain range is formed.
Ex: Himalayas, Pirenees

30.  Transform boundaries (passive)
Two plates slide horizontally against each other. These fractures
are called transform faults. (fallas transformantes)
Earthquakes
Example: San Andreas Fault in
California
Pacific Plate
Northamerican Plate
https://www.youtube.com/watch?v=OjMhUGsF_Nw

31. BENIOFF ZONE = area of seismic activity in a subducting plate

32. Complete:
Type of
boundary
Type of
movement
Ocean floor Landform
produced
Activity
produced
Divergent Separation Creates Oceanic ridges Earthquakes
and volcanoes
Convergent Collision Destroys Trenches,
island archs,
volcanic
mountains,
Earthquakes
and volcanoes
(except continental
collision)
Transform Lateral None transform
faults
ONLY
earthquakes
Activity 5 page 22

33. The lithosphere is divided into blocks
called plates.
Most of the internal geological activity
happens at their boundaries.
Ocean floor is:
generated along the ridges  new oceans
are created
destroyed by subduction in the trenches
 mountain ranges are lifted up
Activities 13, 16 page 17

34. 4.1 The ocean floor
Landforms:
Mid-ocean ridge  volcanic mountain
range under water
Trenches  narrow, deep channels.
They appear as a consequence of
subduction
Faults = perpendicular
fractures which cross
the ridge
Rift = central channel

36.  Composition of the ocean floor
 Volcanic rocks (basalt) covered in marine sediment
 No older than 180 million years
(submerged)

38. basalt
age age

39. 4.2 Sea floor spreading
Magma rises up
from the mantle at
the oceanic ridges
This magma pushes
out the older lava
deposits
We can find
symmetrical bands
of ocean floor
(different ages)
parallel to the axis of
the ridge

40. The ocean floor
spreads and
extends
oceanic lithosphere
is formed at the
ridges
oceanic lithosphere
is destroyed at the
trenches

41. 5.1 Wilson cycle
A. Rift Valley Stage
Magma rises up through fractures making the lithosphere
thinner and lower.
(Drawing 1 and 2 book)

42. B. Red Sea Stage
Deep lakes are formed at the bottom of the valley,
which spreads and spreads.
(Drawing 3 book)

43. C. Atlantic Ocean Stage
New oceanic lithosphere is being
produced aund the Atlantic Ocean
is expanding.
(Drawing 4 book)

44. D. Pacific Ocean Stage
The oceanic lithosphere becomes older
and denser. Subduction zones appear,
where the lithosphere is destroyed.
The Pacific Ocean is getting smaller.
(Drawing 5 and 6 book)

45. E. Indian Continent Stage
The ocean closes as the continents converge.
Marine sediments are trapped and continental
masses join together. A mountain range is formed.
(Drawing 7 and 8 book)
Activities 20, 21, 23 and 24 page 21

46. 5.2 How plates move
Convection currents inside the mantle`
push the plates.
Hot currents not only rise up through
the ridge, but also through hot spots
(puntos calientes).
Gravity pulls down on both sides of the lithosphere.
The sinking plate pulls down (slab pull)
Slab pull force occurs when a denser oceanic plate is forced beneath
a less dense continental plate or oceanic plate in a process called subduction
https://www.youtube.com/watch?v=8LBjaoQe3EE Wilson Cycle video

47. Hot spots

48. Read page 20: 5.3
Development of basic competences: 1, 2, 3 and 4
 seismic discontinuity
 continental drift
 seismic belt
 hypocentre
 seismograph
Review: Continental Drift Video