1. The Internal Processes
Chapter 14
The Internal Processes

2. The Internal Processes
Rigid Earth to Plate Tectonics
Plate Tectonics
Vulcanism
Folding and Faulting
Earthquakes

3. Rigid Earth to Plate Tectonics
Questioning Theories of Rigid Earth
Isostasy
Continental Drift

4. Theories of Rigid Earth
For billions of years Earth has been shaped and reshaped by internal processes
Crust is folded, bent, lowered, raised
Until 1950’s it was believed that Earth was “rigid” or static
Now established that continents drift – plate tectonics

5. Igneous Rock Formation
Igneous rocks form in two layers
Sima = silica+magnesium; oceanic; denser
Sial = silica+aluminum; continental; less dense
Because sima is denser than sial, it subducts the continental plate at convergence i.e., it slides under the less dense plate.

6. Isostasy – Isostatic Rebound
Crust “floats” on denser, deformable mantle
Addition of considerable weight/mass causes crust to sink
Removal of weight allows crust to rise
Example: Glacial and Interglacial periods
Accumulated ice Crust depressed
Ice melts Weight removed
Crust rebounds

7. Continental Drift
450 million years ago, there was only one land mass, Pangaea
250 million years ago, something happened to cause the plates to separate
The separation has been ongoing to the present day
Over millions of years, the shapes and positions of the continents have changed.

8. Continental Drift: Pangaea
Continental drift is the movement of continents over the Earth's surface, and their change in position relative to each other.
Original land mass with continental boundaries

10. Plate Tectonics Seafloor Spreading 3 types of Plate movement
Divergent
Convergent
Transform
Continental Rearrangement
Accreted Terranes and Hot Spots

11. Plates - Seafloor Mid-Atlantic Ridge
The Mid-Atlantic Ridge is an underwater mountain range that runs from Iceland to Antarctica.
It is the longest mountain range on Earth.
The ridge was discovered by Bruce Heezen in the 1950s. The discovery of this ridge led to the theory of seafloor spreading and general acceptance of Wegener’s theory of continental drift.
The ridge runs along a divergent boundary.
Plates - Seafloor
Mid-Atlantic Ridge

12. Plates
Earth's surface is broken into seven large and many small moving plates
Each plate is about 50 miles thick
Each plate moves relative to one another an average of a few inches a year
Three types of movement are recognized at the boundaries between plates: convergent, divergent and transform-fault.

13. 7 Major Plates Eurasion plate (which is covers Asia and Europe)
North American plate (North America)
South American plate (South America)
Pacific plate
African plate (Africa and Middle East)
Australian plate
Antarctic plate
For the most part, each major plate represents one of the seven continents.

14. Major and Minor Plates

15. Plates with Topography

16. Plate Boundaries (a) Oceanic-Continental (b) Oceanic-Oceanic
(c) Continental-Continental
Be familiar with terms circled in red!

17. Convergent Boundaries
Plates move toward each other and collide
Where an oceanic plate collides with a continental plate, the oceanic plate tips down and slides beneath the continental plate forming a deep ocean trench (long, narrow, deep basin.)
This is called subduction
Subduction, occurs at the boundary between the oceanic Nazca Plate and the continental South American Plate.
Where continental plates collide, they form major mountain systems such as the Himalayas.

18. Be familiar with terms circled in red!
Subduction
Be familiar with terms circled in red!

19. Divergent Plate Boundaries
Plates move away from each other, as at the East African Rift
Where plates diverge, hot, molten rock rises and cools adding new material to the edges of the oceanic plates
This process is known as a rift valley
Be familiar with terms circled in red!

20. Be familiar with terms circled in red!
Seafloor Spreading
Divergent Movement of Plates
Sea-floor spreading is the creation of new oceanic crust at mid-ocean ridges
And, the movement of the crust away from the mid-ocean ridges.
Seafloor Spreading
Be familiar with terms circled in red!
Figure 14-5

21. Transform Plate Boundaries
Plates move horizontally past each other
Since the plates are sliding past each other, and not tearing or crunching, they lack the spectacular features found at convergent and divergent boundaries
They are marked in some places by linear valleys along the boundary where rock has been ground up by the sliding
In other places, they are marked by stream beds that have been split in half

22. Transform Plate Boundaries
For example, the San Andreas Fault zone
The Pacific Plate, on which Los Angeles sits, is
moving slowly north westward relative to the North American Plate, on which San Francisco sits.

23. Formation of Accreted Terrane
Small to medium mass of lithosphere carried a long distance by a moving plate
Eventually converges with another plate
Too buoyant to be subducted; it joins – accretes
Often fragments in process
Fragmented
Accreted

24. Accreted Terranes added to western North America over the past 200 million years

25. Formation of Hot Spot
Magma comes to or close to surface at interior plate location – not near plate boundary
Hot spots are relatively stationary for million years
Create volcanoes or hydrothermal vents at surface

26. The Hawaiian Hot Spot A mantle plume here for millions of years
As Pacific plate moved NW, volcanoes created and died, as source of magma shut off

27. Vulcanism Volcanism Distribution of Active Volcanoes Volcanic Hazards
Intrusive Vulcanism

28. Vulcanism
All phenomena connected with the origin and movement of molten rock
Includes volcanic eruptions and solidification of molten material below the surface

29. Volcanism Volcanism is the expelling of magma onto Earth’s surface
The magma is then called lava
Pyroclasic material consists of: lava, rock fragments, solidified blobs of lava, ashes, dust, gas and steam
Pyroclastic material is hurled upward and can be carried in the atmosphere for thousands of miles and over many years

30. Distribution of Active Volcanoes
The heaviest distribution of volcanoes is
the Pacific Ring of Fire

31. Calderas Produced when a volcano explodes, collapses or both
Result is an immense basin shaped depression – usually circular
Depression is many times larger than original volcanic vent

32. Kilauea, Hawaii
The summit area of Kilauea volcano is dominated by collapse features.
Kilauea caldera is a large collapse structure caused by rapid draining of magma between
Genovesa, Gallapogos Is.
The island consists of a single volcano, which emerges only 200 feet above sea level
A breached caldera on the south side of the island forms Darwin Bay
A small lake-filled crater is located in the center of the island.

33. Volcanic Hazards Volcanic gases Lava flows Eruption column & cloud
Pyroclastic flows
Volcanic mudflow

34. Intrusive Vulcanism Shiprock, NM
Magma solidifies beneath Earth’s surface and produces igneous rock
Rock pushed up into crust, before or after solidification, is called igneous intrusion
Shiprock, NM

35. Diastrophism Deformation of Earth’s crust by folding or faulting
Term implies that material is solid and not molten
Rocks bent or broken from extreme pressure in mantle or crust

36. Folding and Faulting Types of Folds Types of Faults Faulted Landforms
Monoclines, Anticlines, and Synclines
Overturned and Overthrust Folds
Types of Faults
Normal
Reverse
Strike-Slip
Thrust
Faulted Landforms

37. Folding
Crustal rocks are bent and folded by forces, such as lateral compression

38. Types of Folds Monocline Anticline Syncline Overturned fold
Overthrust fold

39. Syncline Fold

40. Faulting The breaking apart of rock material from crustal stress
The crust on one or both sides of the break must move
The movement can be vertical or horizontal or both
Usually takes place in a fault zone
Intersection of fault zone with Earth’s surface is called fault line

41. Types of Faults
Normal
Over thrust
Reverse
Strike slip

42. California Fault Line Calaveras Fault, Hollister CA
Strike slip fault in the San Andreas fault system

43. Rift Valley
Northern section of the Great Rift Valley. The Sinai peninsula is in center and the Dead Sea and Jordan River valley above
Rift valley Africa

44. Earthquakes Earthquake Movement (waves)
Magnitude and Shaking Intensity
Hazards
Prediction

45. Seismic Waves

46. Collision of India with Eurasia

47. Earthquake Waves

48. Faulting

49. Transform Faults

50. Folding

51. Seismographs

52. Breakup of Pangaea

53. Formation of Crater Lake

54. Igneous Features

55. Seafloor Spreading and Plate Boundaries

56. Tectonic Settings of Volcanic Activity

57. Terrane Formation

58. Animations http://www.pbs.org/wnet/savageearth/animations/index.html