1. Plate Tectonics, Earthquakes and Volcanoes.

2. How do Scientists Know what is inside the Earth?
Scientists use indirect evidence to determine what is inside the Earth
earthquake waves (SEISMIC WAVES) help determine what is in the Earth
Seismic waves change speed or stop when they enter different materials
This shows that Earth is made of layers

3. Earth’s characteristics change as you travel toward her center.
TEMPERATURE: increases with depth
PRESSURE: increases with depth

4. Layers Within the Earth
The Earth possesses three main layers:
Crust, Mantle, and Core

5. The Crust Earth’s outermost layer Made up of ocean crust-Basalt
Made up of continental crust-granite
Rigid rocky layer of Earth

6. The Mantle The second layer within the Earth
Asthenosphere: upper layer of the mantle that is “plastic” in nature
The plates that carry the continents “float” on the asthenosphere

7. The Core Made of two layers-the outer core and the inner core
Outer Core: liquid sphere of molten nickel and iron
Inner Core: solid ball of nickel and iron

8. Earth’s Magnetic Field
Earth acts as a magnet in space
It has both a North and South pole
caused by fluid movements in Earth’s liquid outer core causing the solid inner core to spin

9. Convection in Earth’s Mantle
Magma is heated by the core, rises to the crust, cools, then again sinks to be reheated
This causes a Convection Current to form in the upper mantle as shown in the diagram below

10. CHAPTER 1; SECTION 3: The Theory Continental Drift
all continents were once joined together in one single landmass scientists called: PANGAEA

11. “Continental Drift”

12. Continents “Drifted” to their current locations….

13. CHAPTER 1; SECT. 4: Sea-Floor Spreading: 1
The ocean floors are not smooth and featureless as once believed
Scientists now know that the ocean floor has a huge mountain range that encircles the globe called the MID-OCEAN RIDGE SYSTEM

14. Sea-Floor Spreading: 3 -diagram-

15. Sea-Floor Spreading: 2 -The Process-
molten material rises from the mantle and erupts
The lava creates new rock at the ridge and pushes old rock to both sides of the ridge
Old Rock is destroyed (remelted) at trenches
This process is called SEA-FLOOR SPREADING

16. Sea-Floor Spreading: 5 -Evidence to support it-
Volcanic activity has been observed at the ridge system
Reversal of magnetic polarity are locked in rocks on either side of the ridge system at equal distances.
Drill samples from the ocean floor are the same age at equal distances from the ridge system. They get older going away from the ridge too.

17. Subduction at Deep-Ocean Trenches
Deep ocean trenches occur where ocean crust is thrust underneath continental crust
Subduction occurs where dense ocean crust is pushed under less-dense continental crust to be re-melted in the mantle
This process occurs over tens of millions of years
This process allows new crust to be created at the ridge systems and old crust to be re-melted; keeping the Earth the same size

18. CHAPTER 1; SECTION 5: The Theory of Plate Tectonics
Explains:
Formation of Earth’s Crust
Movement of Earth’s Crust
Subduction (destruction) of Earth’s Crust

19. Plate Boundaries Edges of crustal plates Transform Boundary:
Plates slip past each other in opposite directions (side to side) Ex: San Andreas Fault
Divergent Boundary:
Plates are moving away from each other
Forms Rift Valleys, mid-ocean ridge
Convergent Boundary:
Plates move toward each other and collide
Forms trenches and mountains

20. Earth’s Plate Boundaries
Prentice Hall, 2000

21. CHAPTER 2: SECT. 1: EARTHQUAKES
A VIOLENT SHAKING OR TREMBLING OF THE EARTH’S CRUST THAT RESULTS FROM MOVEMENT OF ROCK BENEATH THE EARTH’S SURFACE

22. Types of Stress in the Crust: -Shearing Stress-
Stress: a force that can cause rock to change it’s shape or volume
Shearing Stress: pushes rock in two opposite, horizontal directions
Example: San Andreas Fault in California
One plate moves South and the other one moves North

23. Types of Stress in the Crust: -Tensional-
A force that pulls on the crust, stretching rock so that it becomes thinner in the middle.
This occurs when two plates move apart
Example: North East African Rift Zone

24. Types of Stress in the Crust: -Compressional-
Stress that squeezes rock until it folds or breaks
This occurs when one plate collides with another
Example: India and Eurasia; the Himalayan Mountains are continuing to grow due to compressional stresses

25. Faults Breaks in the Earth’s crust where movement occurs
Usually occur along plate boundaries

26. Mountain Building
Over millions of years, stresses can turn flat land surfaces into towering mountains

27. Mountains from Folding
Compressional stresses cause rocks to bend upward or fold
These folds can create alternating hills (anticlines) and valleys (synclines)

28. Mountains from Faults
Faults can cause areas to be uplifted thousands of feet
Fault-Block Mountains:
Areas where paired normal faults uplift blocks of rock forming mountains
Ex: plateaus

29. CHAPTER 2: SECT. 2: EARTHQUAKES
A VIOLENT SHAKING OR TREMBLING OF THE EARTH’S CRUST THAT RESULTS FROM MOVEMENT OF ROCK BENEATH THE EARTH’S SURFACE

30. Chapter 2: Sect. 2: Measuring Earthquakes
Earthquake Focus:
The location within the Earth where rocks break releasing earthquake energy
Earthquake Epicenter:
The point on the Earth’s surface directly above the Focus; greatest damage here
Seismic Waves:
Three types of shock waves that are emitted from the focus of an earthquake; used for study

31. Types of Seismic Waves Primary Waves (P-waves):
First waves to arrive at a seismograph; compress and expand like a sound wave; travel through solids and liquids.
Secondary Waves (S-waves):
Second waves to be recorded; move up and down like a water wave;
Travel through solids only
Surface Waves:
Very slow; P and S waves on the ground. Cause severe ground movement; most damaging form of seismic waves

32. Detecting Seismic Waves
Seismograph:
Device that records ground movements caused by seismic waves
From Prentice Hall 2000

33. Rating Earthquake Strength
Richter Scale
Most widely used method for public reporting
Scale of
Moment Magnitude Scale
Used most often by geologists
Much more accurate

34. Locating an Epicenter
Collect P and S-wave data from three seismic monitoring stations
Calculate the difference in arrival times between P and S-waves
Determine the distance to the epicenter
Draw circles around all three stations with those distances
They will intersect at the epicenter!

35. Earthquake Hazards Liquefaction: Aftershocks: Tsunamis:
Ground shaking is amplified by loose soil; buildings sink
Aftershocks:
Smaller quakes that occur after a larger one
Tsunamis:
Tidal waves that occur when earthquakes occur under the ocean

36. Inside Earth Chapter 3
Volcanoes

37. Chapter 3: Sect 1: What is a Volcano?
A weak spot in the crust where molten material, magma, comes to the surface
Magma: underground liquid rock
Lava: liquid rock at the Earth’s surface

38. Where are volcanoes found?
Ring of Fire:
A geographic region that rings the Pacific Ocean
Many volcanoes occur due to the many plate boundaries that exist in this region
Plate boundaries provide a weak spot in the crust that is necessary for volcano formation

39. Hot Spot Volcanoes
A special volcano that is not located on a plate boundary, but in the center of a plate
Magma melts through the Earth’s crust to spill out onto the Earth’s surface
May be causes by a super-heated plume of magma (scientists are not sure)
Hawaii

40. Chapter 3: Sect 2
Volcanic Activity

41. What makes a Volcano Erupt?
Magma rises toward the Crust because it is hot and less dense than the solid rock around it, however, it gets trapped under the crust
Gases dissolved in the magma build up
Eventually, the gas must escape; and an eruption occurs
The escaping gas pushes the magma out

42. Types of Eruptions: Quite Eruptions
Quiet Eruptions occur with a very fluid, low silica, low gas magma
Example: Mt. Kilauea, Hawaii
Lava slowly oozes out of the volcanic vent

43. Types of Eruptions: Explosive Eruptions
Explosive eruptions occur with a more viscous (thicker), higher silica, high gas magma
Example: Mt. St. Helens, Washington; May 18, 1980
Gas cannot escape the thick lava so it builds up and eventually explodes violently

44. Mt. St. Helens after 1980 eruption

45. Other Volcanic Activity
Hot Springs