1. Plate Tectonics

2. How did it form to the current day earth? EARTH; once upon a time

3. Tectonics Plates
Earth’s crust is now broken to several pieces called crustal or tectonic plates
Each plate has an average thickness of 100km and is composed of both continental and oceanic crust
Plate movement results in various landform appearance

4. Tectonics Plates 9 major plates have been identified: Eurasian plate
Philippine plate
Indo-Australian plate
Pacific plate
North American plate
African plate
South American plate
Nazca plate
Antarctic plate

5. Causes of Plate Movements
Convection currents in the athenosphere
Currents circulate near the base of the lithosphere, cause drag on the bottom of the plates, causing them to move over the surface of the Earth.

6. Plate movements and boundaries
As the plates move, they interact with each other at their boundaries.
3 types of boundaries:
Divergent Plate Boundaries
Convergent Plate Boundaries
Transform Fault Boundaries

7. Plate movements and boundaries
Divergent Plate Boundaries

8. Plate movements and boundaries
Convergent Plate Boundaries

9. Plate movements and boundaries
Transform Fault Boundaries

10. Divergent Plate Boundaries
Zones of Tension
Occurs mostly beneath oceans, few occur within continents
Convection currents diverge (moving apart), the plates are pulled apart
Magma from mantle wells up to fill gap between separating plates.

11. Divergent Plate Boundaries
Cooling and solidification of magma on earth’s surface
Constructive margins formed, where new sea floor (ocean crust )is generated.
New sea floor appears as series of ridges
Sea floor spreading occurs
As plate pulls apart again and new cracks appear, more magma rises to fill gaps creating more sea floor

12. Divergent Plate Boundaries
Rocks found further away from ridge proves that new sea floor is created continuously
Example of divergent plate boundary : Mid-Atlantic Ridge, East African Rift Valley
OLDER ROCKS YOUNGER ROCKS OLDER ROCKS
RIDGES
MAGMA

13. Convergent Plate Boundaries
Zones of Compression
Convection currents converge (coming together), the plates come together
Three types of convergent boundaries
Oceanic and Continental plate collide
Oceanic and Oceanic plates converge
Continental and Continental plates collide

14. Oceanic-Continental Known as destructive margins
Continental plate which is less dense will ride over oceanic plate
Oceanic plate Subducts (forced downwards the mantle), forming a deep elongated trough (ocean trench)
Volcanoes form in subduction zone
As oceanic plates sink deeper, it gradually melts and becomes magma

15. Oceanic-Continental

16. Oceanic-OCEANIC
Less dense oceanic plate ride over more dense oceanic plate
More dense oceanic plate subducts, formation of ocean trench
Magma is force through overriding oceanic plate, forming a chain of volcanic islands
Example: line of islands running from the Aleutians, Japan and down through Philippines

17. Oceanic-OCEANIC

18. Continental-Continental
Collision results in massive land form
No Subduction
Fold Mountain Range tend to form
Example: the Himalayan Fold Mountain Range

19. Continental-Continental

20. Transform fault boundaries
Also known as conservative margins
Two plates slide past each other
Fault-line created
Continental Plate
Continental Plate or Oceanic Plate
Fault-line

21. Transform fault boundaries
Example of a transform fault boundary is the San Andreas Fault

22. Results of Plate Movements
Folding and Faulting
Earthquakes
Volcanoes

23. Folding
When 2 plates collide, the rock strata (layers) will bend and warp as they are compressed
Features of folding: Synclines (downfold) and anticlines (upfold)
SYNCLINE
ANTICLINE

24. Folding Place where rock strata band over is called hinge line
The rock strata on either sides of the hinge is called limbs
HINGE LINE
LIMBS
LIMBS

25. Folding
Types of fold :
Symmetrical fold – both limbs of equal gradient
Assymmetrical fold- one limb steeper than the other
Recumbent fold- Limbs are nearly parallel
Overthrust old- One limb pushed forward so forcefully that the rocks may fracture, and it overrides the other limb. When the overriding limb becomes detached from the main fold, it is called a nappe

26. Folding
RECUMBENT
SYMMETRICAL
NAPPE
ASYMMETRICAL

27. Folding Large scale folding will lead to formation of Fold Mountains
Examples of fold mountains:
The Himalayas
The Andes
The Zagros of Iran

28. Faulting Displaces rocks along a crack or fault line Occurs in 3 ways:
Normal fault
Reverse fault
Tear fault
Can give rise to block mountains and rift valleys

29. Normal fault
When rock strata are under tension caused by forces acting in opposite directions
Tension causes the rock strata to stretch and crack, developing a normal fault
One block of land then moves down (downthrown block) to form an escarpment
Example: The Tenton Mountain in Wyoming USA

30. NORMAL FAULTS

31. Reverse fault When rock strata are compressed
Forces pushing towards each other causes the rock strata to fold, giving rise to reverse fault
One block of land moves up (upthrown block) against the direction of the fault, creating an overhanging scarp
The overhanging scarp collapses due to gravity, weathering and erosion, and produce a gentler slope
Example: Sierra Nevada Mountains of California

32. RESULT FAULTS

33. Tear fault Also known as wrench fault or strike-slip fault
When plates slip past each other horizontally
Tensional or compressional forces act on the rock strata giving rise to tear faults
Big tear faults are known as transcurrent faults
Example: San Andreas Fault in the United States

34. TEAR FAULT

35. Block Mountains
Block raised between 2 parallel fault lines is called a block mountain
If surface is horizontal, it is termed as a horst
if block is tilted, it is termed tilt block
Examples of faulted blocks:
Hawkes bay in New Zealand

36. HORST

37. Rift valleys Also known as a graben Formation can be due to:
land between two parallel lines sink
land on either side of the two parallel lines are unpthrown above the central block of land
two plates pull apart
Example:
The East African Rift Valley
The Red Sea

38. GRABEN http://www.iris.washington.edu/gifs/animations/faults.htm

39. Earthquakes
Vibrations in earth’s crust caused by sudden release of energy
Energy released in the form of seismic waves and that radiate out from the epicentre
Point below the epicentre is called the point of origin where the earthquake originated from

40. Earthquakes Two types of seismic waves: P- waves (Compression waves)
alternately compress and release rocks in the direction the waves are moving
S- waves (Shear waves)
move rocks perpendicularly to the direction the waves are moving

41. Earthquakes

42. Earthquakes Major earthquake zones:
Pacific Ring of Fire -Along the edge of the Pacific Ocean
Trans-Eurasian Belt –Where the Indo-Australian Plate and African Plate meet the Eurasian Plate

43. Earthquakes

44. EFFECTS OF Earthquakes
Displacement of earth’s crust
When earthquakes occur in the ocean floor: Tsunamis (huge tidal waves)
Devastation of cities and loss of lives

45. MOUNT DOOM
Lord of the rings

46. VOLCANOES

47. volcanoes Found along plate boundaries or hotspots
Can be found on land or under water
Volcanoes on land : often form flat cones and the expulsions build up over the years.
Volcanoes under water: often form rather steep pillars and in due time break the ocean surface in new islands.

48. volcanoes
Vulcanicity: when magma is forced towards earth’s surface from within the earth
Hotspot volcanoes: where the location has vulcanism for a long period of time
Example of hotspot volcano: Java Island in Indonesia

49. volcanoes
Most volcanoes on the land are formed at destructive plate margins:
Oceanic crust melt, reduced density force the newly formed magma to rise.
As magma rises it rises up through weak areas in the continental crust, eventually erupting as one or more volcanoes.

50. volcanoes
For example, Mount St. Helens is found inland from the margin between the oceanic Juan de Fuca Plate and the continental North American Plate.

51. volcanoes

52. References. http://www.lostrivers.ca/points/pangaea.gif

53. The End.