Lithosphere 2: Tectonics

1. LITHOSPHERE
2
Tectonics
ppt. by Robin D. Seamon

2. Plate Tectonics
VOCABULARY:
Continental Drift
Alfred Wegner
Plate tectonics
asthenosphere
mantle convection
ridge push
slab pull
deformation
magnetic reversals
sea floor spreading
normal fault
reverse fault

3. Continental Drift:
1912 Alfred Wegner proposed the idea that the
continents were moving away from one another,
breaking from one giant protocontinent he named
(Pangaea); he but didn’t know why.
Today we know that the Earth’s plates float upon
the semi-liquid mantle and move due to:
The Lithosphere moves & changes.
VIDEO: How do we
know plate tectonics
is real? (4:30)

4. http://www.bucknell.edu/x17758.xml
Plate Tectonics-
theory that the Earth’s lithosphere is composed of
10+ plates that fit together like a puzzle
• plates move about 5 cm a year
VIDEO: The Pangaea Pop-up (4:30)

5. http://www.platetectonics.com/oceanf
loors/index.asp

6. Spain
http://www.windows2universe.org/earth/images/earth_plate
s_usgs_L_2_jpg_image.html

7. The plates move slowly on the upper mantle
(asthenosphere)
http://kids.britannica.com/comptons/art-156130/A-diagram-shows-the-relationship-
between-volcanic-activity-and-Earths
Plate Tectonics Explained

8. Movement is caused by mantle convection inside
the Earth
• Hot, less dense fluids go up while cold,
more dense ones go down

9. ridge push: sliding plate force; occurs at mid-
ocean ridges; caused by gravitational force
• spreading happens at the hot magma exit;
less dense
= greater volume
= higher elevation than the
cooler ocean floor beside it
• As plate moves from the boundary, it also
cools, condenses & sinks, creating a SLOPE
• lithosphere slides down
• the PUSH is applied to the tectonic plate due
to gravity

10. slab pull: part of the tectonic process caused by
subduction
• weight of cold, dense oceanic plate dropping
under another plate
• PULLS the oceanic plate down into the
mantle

11. Plates Have Moved

12. Continental “fit”
The continents
look like they fit
together like a
puzzle
EVIDENCE:

13. Correlation of rocks & minerals
Coastal regions of different continents have the
same rocks & minerals
EXAMPLE:
Rocks in the Uwharries of NC near Albemarle are
of the same rhyolite found on the western coast
of Africa
EVIDENCE:

14. Correlation of fossils
Coastal regions of different continents have the
same fossils
EXAMPLE:
fossils of
ancient
species
crossing
continents
EVIDENCE:
VIDEO: What happens when continents collide?

15. Finding fossils in unusual locations
If we find fossils of a species unable to live in that
location today, the plates must have moved
EXAMPLE:
whale &
marine
fossils
found in
Andes
mountains
EVIDENCE:

16. EVIDENCE:
Crustal deformations
• Folding
FOLDING

17. Ocean Floor Evidence
• Age of rocks get older away from the divergent
boundary
• Magnetic Reversals recorded in ocean floor
match on
opposite sides
of the divergent
boundary
EVIDENCE:
VIDEO: What Happens when earth’s
magnetic Poles reverse? (3 min)
VIDEO: Sea Floor Spreading &
magnetic reversals (3 min)

18. EVIDENCE:
Crustal deformations
• Faulting
normal fault: hanging wall move down
reverse fault: hanging wall moves up

19. Plate Interactions
VOCABULARY:
Continental crust
Oceanic crust
convergent boundary
divergent boundary
transform boundary
subduction
uplift
compression
tension
shear
ridge
trench
rift

20. • Two Types of Crust
• Float on the asthenosphere
Oceanic Crust
Density: 3.0 g/cm3
-Cooler
-Sinks below
continental crust
Continental Crust
Density: 2.7 g/cm3
-Warmer
GRANITE
BASALT

21. Convergent boundaries- plate boundaries where
the force of compression pushes two plates
together
Divergent boundaries- plate boundaries where
the tension pulls plates away from one another
Transform boundaries- plate boundaries where
one plate slides past another plate through
shearing
Which subducts?
Continental vs. Oceanic
What happens in the space?
What happens at
these faults?

22. CONVERGENT BOUNDARIES:
Forms volcanic mountain range,
trench & sudden earthquakes
OCEAN CRUST & CONTINENTAL CRUST
SUBDUCTION UPLIFT
FORCE:
compression

23. Aleutian Islands
Ocean-Continent
Subduction
FORCE:
compression
TrenchIsland
chain

24. CONVERGENT BOUNDARIES:
Forms oceanic trench & volcanic
island chain
OCEAN CRUST & OCEAN CRUST
SUBDUCTION
FORCE:
compression

25. Japanese Islands
Oceanic- Ocean
subduction
FORCE:
compression
Trench
Island
chain

26. CONVERGENT BOUNDARIES:
Forms mountains
CONTINENTAL CRUST & CONTINENTAL CRUST
SUBDUCTION UPLIFT
FORCE:
compression

27. Folded Mountains
http://freddoty.com/folded-mountains
Near the Sullivan
River in the Canadian
Rockies The Cape Fold Belt
Mountains, S Africa
http://www.geocaching.com/geocache/GC2CEJP_steytlerville-arch?guid=ff36205a-b979-422c-8266-f7f83ec4d884
FORCE:
compression
VIDEO: Why is Mount
Everest so tall? (5 min)

28. DIVERGENT BOUNDARIES:
Creates sea-floor spreading:
Mid-Atlantic Ridge
FORCE:
tension
OCEAN CRUST & OCEAN CRUST

29. Mid-Atlantic Ridge
FORCE:
tension
Ridge

30. DIVERGENT BOUNDARIES:
Forms rifts & normal faults:
CONTINENTAL CRUST & CONTINENTAL CRUST
FORCE:
tension
Iceland Rift Valley
Rift

31. Nepal
FORCE:
tension

32. Fault-block
Mountains- Nepal
FORCE:
tension

33. TRANSFORM BOUNDARIES:
Creates earthquakes:
San Andreas Fault
CONTINENTAL CRUST & CONTINENTAL CRUST
FORCE:
shear

34. FAULTS LAB- 2 days
6 groups
LAB sheet: Faults Mapping Lab document LINK
Volcanoes document LINK
Earthquakes coordinates document LINK (SMARTNotebook)
MATERIALS:
• 1 large World Map
• Red & blue Expo Markers
• Earthquake slips (3-4 per person in group)
• Volcano slips (divide amongst group)
• Volcano maps
• FAULTS LAB cards 1-6

35. FAULTS LAB

36. Spain
FAULTS LAB

37. EARTHQUAKES
VOCABULARY:
earthquake tsunami
focus initiation
epicenter split
seismograph amplification
Richter Scale
seismic waves
P-wave
S-wave
surface wave
shadow zones
National Earthquake Information Center
Global Seismographic Network
Pacific Tsunami Warning Center

38. Earthquakes: tension builds up at plate
boundaries until the plates slip & tension is
released- we feel earthquakes
VIDEO: What Causes Earthquakes (5 min)

39. • Pressure builds within the crust at the focus
and suddenly breaks along a fault
• The sudden release of energy causes seismic
waves that make the ground shake
• epicenter: place on the surface above the
focus

40. Seismograph- strength of an earthquake is
measured with this tool that records the
vibrations from sensors placed in the earth
http://sydney.edu.au/science/uniserve_science/school/Seismograph/menu.html
http://sydney.edu.au/science/uniserve_science/school/Seismograph/menu.html

41. EarthquakeMagnitude

42. Seismic waves: waves of
energy are radiated from an
earthquake as both body &
surface waves;
2 kinds:
BODY WAVES travel through
earth’s inner layers; faster;
arrive first
1. P-wave- primary wave;
compressional wave;
FIRST WAVE: fastest

43. BODY WAVE
2. S-wave- SECOND WAVES
slower; can only move
through solid rock
(not liquid)
(this is why scientists
deduce the earth’s outer
core is liquid)
• moves particles up and
down or side to side
perpendicular to the
direction the wave is
traveling

44. SURFACE WAVES travel only through the crust;
• lower frequency; seismographs pick up
• damaging waves, sending movement in any
direction on the surface; tearing apart structures
• deeper earthquakes are less destructive

45. Shadow zones- places on Earth’s surface that will
not receive seismic waves because of density of
material
• S-waves are absorbed by the liquid outer core
• P-waves care refracted by the liquid outer core
ANIMATION
Video: Earthquake Seismic Waves (10 min)

47. • Closer a seismic station is to the epicenter
1. The sooner the P-wave will arrive
2. The smaller the difference between P & S
waves
Determining distance from the Epicenter

48. Measure the distance between the first p wave
and the first s wave for each station.
1. Which is the closest station?
CLOSEST
2nd CLOSEST
FARTHEST

49. Earthquake Monitoring
• National Earthquake Information Center- US
(NEIC) determines size & location of
significant earthquakes worldwide & sends
information out, & maintains a database
• Global Seismographic Network (GSN)
worldwide seismic network

51. PRACTICE

52. Use ESRT pg 11
• Travel time:
amount of time
it takes for
seismic waves to
reach
seismograph
station
• Epicenter
distance:
distance from
the seismograph
station to
epicenter

53. Use ESRT pg 11If you are asked the
travel time of a P-
wave or S-wave for a
given epicenter
distance:
1. Go to the
epicenter distance
on x-axis, then up
to correct curve
2. Go over to the y-
axis & determine
travel time
How long does it
take a P-wave to
travel 2,000 km? X 1000 km
ANSWER: 7 min
20 sec

54. Use ESRT pg 11If you are asked the
epicenter distance of
a P-wave or S-wave for
a given travel time:
1. Go to the travel
time on y-axis,
then go over to
correct curve
2. Go down to the x-
axis to determine
epicenter distance
How far can an S-
wave travel in 11
minutes? X 1000 km
ANSWER: 3,300 km

55. Use ESRT pg 11If you are asked the
arrival time of an
earthquake wave and
given the epicenter
distance & origin time:
1. Determine travel
time of wave
2. Add travel time to
the origin time
given
If an earthquake occurs
at 3:13:00, what time
did the P-wave arrive
at the seismic station
2,400 km away?
X 1000 km
ANSWER: 3:13:00
+ 4:40
3:17:40

56. Use ESRT pg 11If you are asked the
origin time (the time
the earthquake
occurred):
1. Determine travel
time of wave
2. Subtract arrival
time you were
given minus the
travel time
If a P-wave arrives at a
station 5,000 km awa
at 11:10:00, what time
did the earthquake
originate?
X 1000 km
ANSWER: 11:10:00
- 00:08:20
11:01:40

57. Use ESRT pg 11If you are asked to determine
the difference in arrival time
between P & S waves
1. Line up a scrap paper
vertically on epicenter
distance given
2. Mark locations where P &
S waves intersect on
scrap paper
3. Line up scrap paper on y-
axis with one point on 0
minute mark
4. The second mark will be
the difference in arrival
time

58. Use ESRT pg 111. Line up a scrap paper
vertically on epicenter
distance given
2. Mark locations where P &
S waves intersect on
scrap paper
3. Line up scrap paper on y-
axis with one point on 0
minute mark
4. The second mark will be
the difference in arrival
time
An epicenter station is
8,000 km away. How long
after the first P-wave did
the first S-wave arrive?

59. Use ESRT pg 111. Line up a scrap paper
vertically on epicenter
distance given
2. Mark locations where P &
S waves intersect on
scrap paper
3. Line up scrap paper on y-
axis with one point on 0
minute mark
4. The second mark will be
the difference in arrival
time
An epicenter station is
8,000 km away. How long
after the first P-wave did
the first S-wave arrive?
ANSWER: 9
min 20 sec

60. Locating the epicenter
Determining the location requires distances
from three stations.
• This will determine the location on a circle
with the radius being the distance from that
station to the epicenter.
• Using data from 3 stations, scientists can
triangulate where the epicenter is:
• Where the 3 circles intersect
= epicenter

61. 1. Which seismic station is closest to the
epicenter?
ANSWER: Station A because the circle is
smallest

62. Deadly Hazards
• Shaking ground causes buildings, roads and
bridges to shake, roofs cave in
• Poorly constructed buildings in
underdeveloped countries, especially
devastating
Haiti Earthquake
2010
Magnitude 7.2
230,000 died

63. 15,900 + died
Japan Earthquake Pictures, Video (9 min)
Tohoku Earthquake, Japan
2011
Magnitude 9.1

64. Causes of Earthquakes:
1. natural pressure buildup
2. groundwater extraction
3. wastewater injection
Destruction dependent upon:
1. Intensity & duration of the vibrations
2. Nature of the material where a structure is
built
3. Design of the structure

65. Earthquake Protection
• Build on stable ground
• Use modern earthquake-stable designs for
houses and bridges

66. IN HOME: seek cover against an interior wall;
protect head; avoid mirrors/windows & tall
furniture

67. Tsunami: when an
earthquake or volcanic
eruption happens under
the ocean
1. Initiation: under-ocean
earthquake
2. Split: created wave
splits: one moving
towards ocean, one
towards shore
3. Amplification: front of
wave gets taller as it
moves toward shore
VIDEO: How Tsunamis work
3:30

68. Deadly Hazards
• Speeds faster than a jet liner
• Heights rise 40 feet or more before crashing
on shore
• 50,000+ people killed this century
• 1998 Paupa New Guinea earthquake: 2,200
killed

69. VIDEO: Rare Video: Japan Tsunami (3:30)
Japan Tsunami- 2001
9.0 Earthquake

70. • On shore, a person would see the water
receding from shoreline as it gathers with the
upcoming tidal wave.

71. • Pacific Tsunami Warning Center- 1948; collects
seismic data from 26 member countries; keeps
watch for suspicious shaking that might trigger
tsunamis;
• Palmer, Alaska- warning center that monitors
coasts specific to British Columbia, Washington,
Oregon, & California
• When an earthquake of 7/5 magnitude or greater
near/under the ocean occurs, these warning
centers send out initial alerts to all local
authorities within 3 hours of tsunami travel time
• Local authorities decide on evacuation plans

72. Earthquake map BACK
http://pubs.usgs.gov/fs/2003/fs017-03/images/useqs.gif

76. VOLCANOES
VOCABULARY:
volcano
shield volcano
cinder cone volcano
composite volcano
caldera
Ring of Fire
hotspot
lava
lahar
ash
acid plumes
glass shards

77. Pressure under the crust becomes great within a
magma chamber & must come out… volcanoes
Volcanoes: cracks in the crust where lava flows
1. shield volcanoes
2. cinder cone volcanoes
3. composite volcanoes

78. Mauna Kea, Hawaii
(shield volcano)
http://www.uhh.hawaii.edu/~csav/gallery/decker/hawaii_mauna_kea.php
http://www.the-vu.com/2010/05/mauna-kea-in-hawaii-driving-to-the-
summit-of-this-grand-volcano/
Shield volcano: layers of lava released from non-
explosive eruptions
Hawaiian islands are on a hot spot in
the center of the Pacific plate

79. Paricutin, Mexico
photo2.si.edu/mexvolc/volcmex.
htm
Cinder cone volcano:
pyroclastic material- dust
& ash explodes out

80. Mt. Fuji
Mount St . Helens
ruby.colorado.edu/.../Volcanix/Volc
anix.html
Composite volcano:
pyroclastic explosions
followed by slower, longer
flowing-lava (Mt. St.
Helens

81. Caldera: large,
semicircular pit
that forms when
the chamber
supplying
magma to a
volcano partially
empties, then
the roof
collapses; sinks
the ground
thinkgeoenergy.com/archives/747

82. Volcano WATCH IT!
http://earthobservatory.nasa.gov/images/imagerecords/16000/
16689/ISS013-E-24184_lrg.jpg
http://hvo.wr.usgs.gov/kilauea/update/archive/2008
/Feb/20080228-3564-TRO_L.jpg
http://volcano.oregonstate.edu/vwdocs/vwlessons/
rocks_pics/lava_flow.jpg
VIDEO: The colossal
consequences of

83. Ring of Fire
Major area in Pacific Ocean basin where many
earthquakes and volcanic eruptions occur

84. Yellowstone Volcano, Wyoming
Enormous caldera & super-volcano under the surface
• 40 mile crater
• last eruption: 640,000 ya
• 1000-2000 earthquakes a year
(most below 3 magnitude)
• an eruption would be 1000X
more powerful than Mt St.
Helen’s in 1980
• hydrothermal water features
are evidence it is still active
• most scientists believe that
weeks of warning signs will
alert us; 1/700,000 chance a
year it will erupt
CURRENT
CONDITIONS LINK:

85. Yellowstone Hotspot
hotspot- thermally expanded buoyant mantle that
lifts an overlying plate
-used to track motion of tectonic plates: hot plate
stays put as plate moves across it

86. Craters of the Moon National Monument, Idaho
-final stage of the Yellowstone hotspot volcanism
-result of volcanic flow and a rift valley (62 miles in
the park)

90. VOLCANIC GEOHAZARDS
• lava- magma that reaches the surface

91. GEOHAZARDS
• lahar- destructive mudflow on the slopes of a
volcano

92. GEOHAZARDS
• ash- volcanic ash clouds the sky and adds to
acid rain & air pollution
Ontake,
Japan 2014

93. GEOHAZARDS
• acid plumes & glass shards – sulfur dioxide
gas & very fine glass shot into the sky as Mt.
Kiauea volcano vents 7/2018
VIDEO 1 min

94. Mt. Saint Helens, Washington

95. Cone is
rebuilding 2018

97. • Scientists study and monitor seismic activity
at a volcanic hot zone
• In scientific observatories & through field
work, scientists look for warning signs of an
eruption
• small earthquakes
• inflation/swelling of the land
• increased emission of heat/gas from
vents
Kilauea Observatory,
HI

98. Official Volcano Warnings
• color codes & alert levels
• specific for each volcano
• warning systems are based on probability of
eruption

99. Safety After a Volcano
• cover mouth &nose
• wear goggles/protect eyes
• cover skin
• clear roofs from heavy ash