1. Plate Tectonics

2. Plate Tectonics

3. Continental Drift
Alfred Wegner—1st to propose the theory of continental drift
His theory– Continents were once a single landmass then, over time, they broke up and drifted to where they are today

4. Wegner’s Evidence of Continental Drift
Fossil Evidence
Rock formations
Climatic Evidence
Geographic Evidence

5. Fossil Evidence

6. Let’s do a puzzle!
Fossil puzzle…match up the fossils on the continents to view Wegner’s evidence of continental drift

7. Rock Formations
Just like fossils, similar rock formations were found on different continents

8. Climatic Evidence
Shows that land used to have different climates than is natural to have in the current position of the land
Example: Tropical plant fossils
were found in Antarctica

9. Geographic Evidence
Shapes of continents look like they fit together and have similar geographical features

10. FYI
*As continents rift or as mountains form, populations of organisms are separated. When
populations of organisms are separated, new species may evolve from existing species.
*Similar rock formations and fossil evidence supported Wegener’s evidence.

11. Mid-Ocean Ridges
--a place where crust is spreading an creating new ocean floor --a place where old crust is recycled (this process makes oceanic crust younger than continental crust)

12. Lets make a mid-ocean ridge!
ACTIVITY!!!!!!!!!
Lets make a mid-ocean ridge!

13. Sea-Floor Spreading
Harry Hess hypothesized that the valley at the center of mid-ocean ridges was a crack in the Earth’s crust
At this crack, magma rises up to form new sea floor which cools and forms new sea flooring
This process is known as sea-floor spreading

14. Layers of our Planet

15. Layers of our Planet
Lithosphere – the solid, outer layer of Earth that consists of the crust and the rigid upper part of the mantle
Asthenosphere – The solid, plastic or putty-like layer of the mantle beneath the lithosphere. Made of mantle rock that flows very slowly, which allows tectonic plates to move on top of it

16. Theory of Plate Tectonics
This is the theory that explains how large pieces of lithosphere called plates, move and change shape

17. Tectonic Plates
Scientists have identified about 15 major plates:

18. Plate Tectonics Activity

19. Types of Plate Boundaries

20. Divergent Boundaries
These types of boundaries move AWAY from each other
Examples: Mid-ocean rifts, the Red Sea (between the African and Arabian Plates)

21. Convergent Boundaries
Plates collide together at these types of boundaries
Examples:
Areas of subduction
Mountain ranges
Ocean trenches
trench

22. Transform Boundaries
A boundary at which two plates slide past each other horizontally
Example:
San Andreas Fault in
California

23. The Supercontinent Cycle
The process by which supercontinents form and break apart
This happens because tectonic plates of the Earth are always moving, though very slowly

24. 450 Million Years ago
Near the end of the Precambrian time Earth’s continents were separated…not as much land was above water as today

25. 250 Million Years Ago
By the end of the Permian Period, Pangaea had formed

26. 150 Million Years Ago
Pangaea had split into two continents, Laurasia and Gondwanaland

27. 60 Million Years Ago
Continents were moving toward their current positions on Earth

28. Future?
Scientist propose that in about 250 million years the earth might look like this:

29. Earthquakes

30. What is an Earthquake?
Earthquake--Occur when rocks under stress shift along a fault (energy released)
Fault—break in rock where one block moves relative to another

31. Let’s Build a Fault Model!

32. Damage from Northridge Earthquake in Southern California--1994

35. Anatomy of an Earthquake
Focus--1st motion of earthquake in Earth, along fault
Epicenter—point on Earth’s surface directly above focus
90% of continental earthquakes have shallow focus—most damaging

36. Parts of an Earthquake

37. Elastic Rebound
Elastic Rebound—sudden return of deformed rock to undeformed shape
Elastic rebound causes earthquakes

38. Fence offset due
to Elastic Rebound

39. Seismic Waves
When rocks on a fault move, they release energy as seismic waves
Seismic waves travel outward from the focus in all directions

40. Body wave—seismic wave that travels thru a medium
two types: P-wave & S-wave

41. Seismic Waves
P (primary) waves are the fastest & travel thru solids, liquids, & gases

42. Seismic Waves
S (secondary) waves are 2nd fastest & travel thru solids only. Although slower they can cause the most damage

43. Seismic Waves
Surface wave— a seismic wave that travels along surface of medium. These are S & P waves that reach the surface & can cause greatest damage

44. Water Wave and Slinky Activities!

45. WAYS TO MEASURE AN EARTHQUAKE
There are two major scales to measure an earthquake:
Mercalli Scale: measures earthquake intensity (by amount of damage caused)
Richter Scale: measures earthquake magnitude (strength)

47. Studying Earthquakes Seismology—study of earthquakes & seismic waves
Seismograph—records vibrations in ground
Seismogram—tracing of EQ motion, recorded by seismograph

48. Bill Nye on the Richter Scale http://www. youtube. com/watch
Bill Nye on the Richter Scale Bill Nye on Waves Earthquake recording station/seismograph clip

49. SEISMOGRAM Order of recording: P-waves, S- waves, then surface waves
Shows S-P lag time

50. P-Wave
S-Wave
S-Wave
S-Wave
To find S-P lag time, subtract where the P wave starts from where the S wave starts (S-P = Lag Time)

51. What is S-P lag time for San Francisco, CA?
What is S-P lag time for El Paso,TX?
28 sec – 0 sec = 28 sec lag time
What is S-P lag time for San Francisco, CA?
120 sec – 0 sec = 120 sec lag time
What is S-P lag time for Seattle, WA?
165 sec – 0 sec = 165 sec lag time
Which city is closest to the epicenter?
The city with the shortest lag time is closest to the epicenter, so it’s El Paso, TX

52. Locating Earthquakes Through Triangulation
S-P lag times are analyzed to find the epicenter of Earthquakes using 3 stations
Why 3 stations?
Because all we know is distance, so it takes 3 circles to narrow it down to one point
Epicenter

53. Let’s stop here and practice finding S P lag time

54. Fault Zones
Fault zone—region w/ lots of faults that typically form at plate boundaries
Fault zones and earthquakes can occur away from plate boundaries as well

55. Fault Zones—New Madrid
New Madrid fault line—New Madrid, MO—120 miles southward on I-55
1811/1812—most widely felt series of E.Q. in U.S. history (2000+)
Five were 8.0+
Ancient fault zone deep in crust of Mississippi River region

57. Tsunamis
Tsunami—giant ocean wave that forms after volcanic eruption, submarine earthquake or landslide
May form when ocean floor rises due to earthquake
Tsunami animation

58. Japan’s Tsunami Before and After…(Google Earth)

60. Volcanoes
Erupting with fun!

61. Magma vs. Lava
Magma is liquid rock produced under the Earth’s surface but Magma becomes Lava as soon as it leaves the Earth and flows outside.
Lava
Magma

62. Magma
Magma can form under three conditions: 1. If rock temperature rises above its melting point then it will melt into magma 2. Rock can melt when too much pressure is removed from rock that is above its melting point 3. The addition of fluids, such as water, may lower the melting point of some rock and cause it to melt

63. Volcanism
Volcanism is any activity that includes the movement of magma onto Earth’s surface
A volcano is a vent or fissure in Earth’s surface through which magma and gases are expelled

64. Location and Formation Of Volcanoes
Most volcanoes occur in convergent and divergent boundaries of tectonic plates A major zone of active volcanoes is located in the “Pacific Ring of Fire” which is also a major earthquake zone

65. Locations of Volcanoes
Some tectonic boundaries include:
Subduction Zones
Mid-Ocean Ridges
Hot Spots

66. A subduction zone is where one tectonic plate moves under another
Subduction Zones
A subduction zone is where one tectonic plate moves under another

67. Mid-Ocean Ridges
A long, undersea mountain chain that has a steep, narrow valley at its center.
Forms as magma rises from the asthenosphere
Creates new ocean floor as tectonic plates move apart (sea floor spreading)

68. Hot Spots
Areas of volcanism within the interiors of lithospheric plates
The Hawaiian Islands were created by a hot spot
See HOT demo!

69. Types of Volcanic Eruptions
Quiet volcanoes have mafic magma which is rich in magnesium and iron. Mafic magma is dark in color with runny lava
Explosive volcanoes have felsic magma which is rich in light-colored silicate materials and is thick and sticky.
Compare water boiling (quiet volcano) to thick spaghetti sauce boiling (explosive volcano)

70. Pyroclastic Materials
“Pyro” means fire
Pyroclastic materials include fragments of rock that form during volcanic eruptions

71. Types of Pyroclastic Materials (from smallest to largest
Volcanic dust
Volcanic ash
Lapilli—means little stones…they normally fall near the vent
Volcanic bombs—clots of lava that are thrown out of the volcano & become round or spindle shaped as they go through the air
Volcanic blocks—solid rock that is blasted through the vent…some are as big as a house!!

72. Read “What Volcanoes Can Produce”

73. Types of Volcanoes Shield volcanoes Cinder Cones
Composite Volcanoes (Stratovolcanoes)
Calderas

74. Shield Volcanoes Wide base Gently sloping sides
Forms from quiet eruptions

75. Cinder Cone Volcanoes Steep slopes
Form from explosive eruptions and are made of pyroclastic materials

76. Composite Volcanoes (Stratovolcanoes)
Made with alternating layers of hardened lava flows and pyroclastic materials
This type of volcano alternates quiet and explosive eruptions

77. Calderas
This type of volcano is created when the magma chamber below a volcano empties and the cone collapses
The collapse leaves a large basin-shaped depression (crater)
Some calderas eventually fill with water to become lakes

78. Read “What Are Volcanoes?” and answer questions