1. The Dynamic Earth

2. The Earth
What's inside
the Earth?

3. Structure of the Earth

4. Plate Tectonics

5. The World Today

6. Science At Work: Alfred Wegner
In 1915 Alfred Wegner proposed a radical theory.
He suggested that there was once a super continent called Pangaea.
Pangaea then split up to form the continents that we know today.
These then drifted into their current positions

7. Pangaea – 250 million years ago
Australia

8. Pangaea to Now

9. Pangaea to Now

10. Pangaea to Now

11. Evidence - Migration of reptiles

12. Evidence - Mountains
The rock type, composition and formations of mountains in eastern North America are similar to those of mountains across north-western Europe.

13. Evidence – Coal Coal has been found above the Arctic circle.
As coal comes from decomposed plants and it is far too cold now to support plants, it must have once moved from a warmer climate.

14. Evidence – Magnetic Alignment
Although the magnetic alignments of ancient rocks all point in different directions, they all point in the same direction when the continents are joined.

15. Future Earth? A

16. Future Earth? A A

17. Questions:
What evidence suggests that the continents were once joined?
Correct these statements to make them true.
Coal deposits above the Arctic Circle suggest the land has floated there from warmer climates
Continents that do not have glaciers now have always been too warm to have them.
Triassic reptiles could have swum the distances required to populate different continents.

18. Evidence from below

19. World War II - Sonar
During WW2 the military developed new technology called Sonar.
This technology allowed the military to get accurate maps of the ocean floor for their submarines.

20. Sonar Results Sonar revealed some interesting results:
That huge underwater volcanic mountain ranges run down the centre of the oceans.
The ages of the rocks of the ocean floor vary from ‘brand new’ to 200 million years old. (this is younger than the rock of the continents).
The rock of the continents is less dense than the ocean floor and seems to float on it.

21. Evidence – Magnetic Stripes
Ridge
The seafloor has been widely mapped by magnetometers. As the oceanic plates grow the magnetic zones form distinct stripes on the map. This map is coloured according to the age of the rocks
The stripes show that the youngest rock is next to the ridges and the oldest next to the trenches.
Red = 0 – 9.7 mya Blue = – 180 mya
Green = mya
mya = Million Years Ago

22. Magma and the Ocean
The ocean floor is a conveyor belt dragging new rock from mid-ocean and in the trenches.

23. All the evidence suggests that the molten rock is emerging along the mid-ocean ridges.
As the molten rock hits the water it cools, building new mountains.
These new mountains push the old ones out of the way.
The ocean floor acts like a conveyer belt, carrying everything towards the trenches.

24. Floating plates

25. Inner Structure of Earth
The earth is made up of layers we live on the crust.
Next is the Mantle which is approx 2800 km thick.

26. Keeping the mantle hot
While the mantle tries to cool the crust helps to keep the heat in.
Patches are also heated by the decay of radioactive elements such as Uranium, Thorium and Potassium.

27. Convection currents
Just as hot air and liquid rise, so will hot liquid rock. Any rock over a hot patch in the mantle will rise and ‘cooler’ rocks will drop.
This cycle is called a convection current and it takes millions of years to complete.

28. Convection currents
Analogy: The Slabs of crust float on these convection current, are like pieces of toast floating on a very thick soup. The toast moves if the soup is stirred. The bottom of the toast also gets a little soggy. The slabs of crust, soggy bottom and top layer of the mantle move as one and are called tectonic plates.

29. Questions: What causes convection currents?
How long do convection currents take to cycle around the mantle?
What keeps the mantle from cooling down and becoming solid?

30. At the Edges

31. Tectonic Plates and their Boundaries

32. Types of Plate Boundaries
There are three types of plate boundaries :
A) Divergent: Each plate is moving away from the other
B) Convergent: Two plates that are moving towards each other.
C) Transform: The two plates are sliding past each other.

33. Example - Spreading
As plates move apart they create cracks and form rift valleys.
This allows hot magma to rise into the gap.
This means old rocks are pushed out of the way as the magma cools to form new rocks.
An example of two spreading plates are the African plate and the Arabian peninsula.
Fact: Some plates have been measured as moving apart at a rate of 20cm a year!

34. Spreading plates: Another way of thinking about it.
Its like a wound (rift valley).
A scab (Rock) begins to repair the wound but any stress cracks it.
This allows blood (Magma) to ooze out.
A new scab then needs to be made.
A Scab

35. Science at Work: Helgafjell Volcano
The Helgafjell Volcano Iceland
The Helgafjell Volcano near Iceland is an example where volcanic eruptions caused by two spreading plates has created an island.

36. Example – Convergent

37. Convergent plates form big mountains
The Himalayas formed when the plate that carries India collided with the Eurasian plate.
Both plates have similar densities and instead of one going under the other they push against each other.
This forms extremely large mountains.

38. Example - Transform

39. San Adreas Fault
Transform boundaries are formed by plates scraping against each other.
This doesn’t make mountains or volcanoes, it creates earthquakes.
The most famous transform boundary is the San Andreas Fault.
This fault lies directly under San Francisco and Los Angeles.
Fact: Every year the coast of California moves 5cm this is making L.A closer to San Francisco

40. Normal and Reverse faults
Faults are lines of weakness in the earths crust.
Normal faults are caused from movement away from each other. The results is the formation of cliffs and overhangs.
In reverse faults movement is towards each other. This causes the two surfaces to overlap.

41. Questions: Can you think of an example of a land mass that:
That has broken away from the main mass of Australia?
Outside of Australia?
Label the boundaries on
this slide

42. What caused such destruction?

43. Earthquakes

44. Science at work: Quake Lakes
May 14th 2006
May 15th 2008
May 19th 2008
A satellite image shows the Yansai Lake forming from a river at Tangjiashan in south-west China's Sichuan province. This was the direct result of an earthquake that devastated the region on May 12.

45. Richter Scale
The Richter magnitude scale was developed in 1935 by Charles F. Richter.
On this scale an earthquake registering a 6 on the Richter scale is 31 times more powerful than one registering a 5.

46. Richter Scale Measurement
Earthquake effects 3
Felt slightly in areas near the epicentre 4
Felt by most people up to several kilometres from the earthquake. Some objects upset. 5
Strongly Felt. Some damage to weak buildings. 6
Moderately destructive. Some severe damage to weak buildings. 7
Major earthquake. Destruction of many buildings. 8
Very destructive. Total destruction of structures.

47. Epicentre and Focus
The focus is the point at which the earthquake starts.
The epicentre is the point on the surface directly above the focus of an earthquake.

48. Seismic waves Seismic waves can be spilt into two categories:
Body waves which travel through the body of the earth. These can be either:
Primary (P)
Secondary (S)
Surface waves travel along the surface. These can be either:
Rayleigh (R)
Love (L)

49. Body Waves
P waves are the fastest and are the first to be recorded. This is because:
P waves travel through solid and liquid rock.
While S waves travel only through solid rock, being stopped by liquid rock. Therefore they travel along the surface.

50. Surface Waves
R waves are rolling waves. They are usually quite small (1cm)
L waves arrive last and travel in an up and down motion.
Together they cause cracks in the surface, which then swallow and crush the objects above them.

51. Science at Work: Boxing Day Tsunami 2004

52. How Tsunamis Happen

53. How Tsunamis Happen

54. Useful animations http://news.bbc.co.uk/2/hi/asia-pacific/5194316.stm

55. Activity: Earth Quake Tower
Your task is to build a tower that will be able to survive an earthquake.
You will have a limited amount of materials to use so plan first!
The best tower team will win a prize.

56. Volcanoes

57. Volcanoes

58. Types of Volcanoes

59. Shield Volcanoes The biggest volcanoes are shield volcanoes.
Mauna Loa - Hawaii
The biggest volcanoes are shield volcanoes.
They get larger every time they erupt
However their eruptions are more predictable and less explosive.

60. Composite Volcanoes Composite volcanoes are the most dangerous.
Mt Fuji
Mt St Helens
Mt Vesuvius
Composite volcanoes are the most dangerous.
They erupt explosively and violently.
Examples are Mt Fuji (Japan), Mt St Helens (USA) and Mt Vesuvius (Italy).

61. Volcanos form islands
Krakatau, Indonesia

62. Useful Website

63. Mining

64. Diavik Mine, Canada
This incredible mine can be found 300km northeast of Yellowknife in Canada. (It's amazing that it doesn't fill up with water, being surrounded by it.) The mine is so huge and the area so remote that it even has its own airport with a runway large enough to accommodate a Boeing 737.

65. Mirny Diamond Mine, Serbia
This mine is an absolute beast and holds the title of largest open diamond mine in the world. It is 525 meters deep with a top diameter of 1200 meters. There's even a no-fly zone above the hole due to a few helicopters being sucked in.

66. Bingham Canyon Mine, Utah
This is supposedly the largest man-made excavation on earth. Extraction began in 1863 and still continues today. The pit is constantly increasing in size. In its current state the hole is 3/4 mile deep and 2.5 miles wide.

67. Kimberley Big Hole - South Africa
Apparently the largest ever hand-dug excavation in the world, this 1097 meter deep mine yielded over 3 tonnes of diamonds before being closed in The amount of earth removed by workers is estimated to total 22.5 million tons.