
Here's a rap about plate boundaries that get's stuck in my head all the time:

https://www.youtube.com/watch?v=dkELENdZukI

This is how our continents have moved around over time due to plate tectonicswith dramatic music!

https://www.youtube.com/watch?v=uGcDed4xVD4

And lastly, because I think it is super cool to see, here is India colliding with Asia to
form the Tibetan plateau and Himalayas:

https://www.youtube.com/watch?v=loFxYSHxTf0
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Announcements
 TA evaluations
 https://catalyst.uw.edu/webq/survey/tansy/254493
 Last day to submit extra credit is this Friday (12/5)
 Assignments on Canvas site
 Submission to Canvas site
 No scheduled lab this week
 Print Lab #8 and take it with you to the Burke Museum to explore “The Life and
Times of Washington State” exhibit
 Free with student ID
 Must ask for & attach admission receipt to receive full credit for lab
 Final exam scheduled for Wednesday, December 10th 2:30-4:20pm in MGH 389
 Study guide posted to “Exams” link
 Review sessions Monday (12/8) and Tuesday (12/9) from 3:30-5pm in the Ocean
Sciences Bldg (OCN) 425
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What will you be doing in lab this
week?
 No scheduled lab this
week
 Visit the Burke Museum to
view the “Life and Times
of Washington State”
exhibit
 Open 10am-5pm
 Free with student ID
Located on the corner of 17th Ave
NE and NE 45th Street
 Must ask for and attach
admission receipt to get
full credit for assignment
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Earthquakes, volcanoes,
tsunamis…oh my…
It’s not a question of if, but when…
…predicting the next big earthquake.
 What geologic processes that form(ed) Washington state?
 What are earthquakes?
 What’s happening in the Earth’s interior?
 Cross section of Earth
 How do the continents move? Where is new seafloor being created
 Plate tectonic
 Types plate boundaries
 What does the seafloor look like?
 Is there life down deep?
 What is the energy source?
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http://www.washington.edu/burkemuseum/earthquakes/
It’s a question of when
Nisqually Quake: http://www.youtube.com/watch?v=PY5Rm5TGNy0
Simulation of Viaduct
Collapse:http://link.brightcove.com/services/player/bcpid1509319618?bctid=4639
What do you notice? What do you
wonder?
Fig. 3.10 – Earthquake epicenters
Fig. 3.8 First physiographic chart of the seafloor
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What are earthquakes?
 An earthquake is the sudden
shift of rock along a fracture in
the Earth
 Releases energy
 Energy travels in waves to the
surface and makes the ground
shake
 Earthquakes occur everyday
across the planet
 http://earthquake.usgs.gov/
earthquakes/
 Can originate at the surface
or as deep as 650 kilometers
(400 miles)
 Point or plane of rupture is
known as the focus or
hypocenter
 Epicenter is the place on the
surface of the earth
immediately above the focus
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The planet is layered, like a giant
hard boiled egg
Fig. 3.3
 The crust, the outermost layer, is rigid
and very thin compared with the other
layers
 Ranges in thickness from about 5
kilometers (3 miles), beneath the
oceans, to up to 65 kilometers (40
miles), under mountains on
continents
 Below the crust is the mantle
 Dense, hot layer of heat-softened
rock approximately 2,900 kilometers
(1,800 miles) thick
 At the center of the Earth lies the core,
 Twice as dense as the mantle
because its composition is metallic
(iron-nickel alloy)
 Liquid outer core and solid inner core
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Earth’s interior
 Lithosphere is formed by
the fusion of crust and
mantle
Fig. 3.5
 Strong, rigid surface shell
(plates)
 Rides on top of
asthenosphere which is
weak, partially molten
and deformable (due to
pressure and
temperature)
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Cracked egg - tectonic plates
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Plates are constantly moving and
Fig. 3.21
changing
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Fig. 3.36
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13
14
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What causes plates to move?
 Convection currents within the
mantle transport the plates
 Heat from core produces the
convection currents
 As the heat rises, it spreads away
from a central point and carries the
plates with it
 Plate interaction results in
earthquakes
 Creation of crust
Fig. 3.9
 Slab pull
 Subduction of dense materials pulls
plates apart
 Destruction of crust
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Three Types of Plate Boundaries
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Transform fault boundary
 The zone between two
plates sliding horizontally
past one another is called a
transform-fault boundary
 Crust is not created or
destroyed
 Most transform faults are
found on the ocean floor
 Best known occur on
land
 San Andreas fault
zone in California
 Commonly offset the
active spreading ridges,
producing zig-zag plate
margins
 Defined by shallow
earthquakes
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Divergent boundaries
 Divergent boundaries occur at spreading centers where plates are
moving away from each other and new crust is actively being formed
by magma rising from the mantle
 Ocean basins are created along divergent boundaries that break apart
continental lithosphere
 Mid-ocean ridge is the largest feature on the planet
 Covers 23% of Earth’s surface
Fig. 3.22
 What features are associated with
divergent boundaries?
 Hydrothermal vents
 Seamounts (usually extinct volcanoes)
 Earthquakes
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Divergent boundaries - Continental rifting
and the formation of ocean basins
 Rifting begins as rising
magma heats overlying
crust
 Stretching and pulling
apart of crust produces a
rift valley with active
volcanoes
 Continental spreading
results in formation of
new seafloor
 Where is this currently
happening?
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Convergent boundaries
 Two plates crashing together is
known as a convergent
boundary
 Occurs at ocean-ocean,
ocean-continental and
continental-continental
margins
Fig. 3.22
 One plate sinks or subducts
under the other plate
 Which plate sinks?
 Densest
 Which one is the densest?
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Ocean-continental convergence
 Which plate subducts?
 Denser plate
 Oceanic
That’s what our
own convergent
boundary does!
 What features are associated with oceancontinental convergence?
 Volcanoes (Cascade Mountains)
 Trenches form
Fig. 3.30
 Usually parallel to continent
 Do we see one along our coast?
 Earthquakes
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Oceanic-oceanic convergence
 Plate with edge furthest from
spreading center is subducted
 Oldest plate subducts
Fig. 3.30
 What features are associated with
ocean-ocean convergence
 Trench
 Volcanoes (island arc)
 Earthquakes
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Continental-continental
convergence
 Plate that is attached to oceanic
crust subducts
 Continues to drag continental crust
beneath the other crust
 Scrapes sediments from oceanic
lithosphere
 Olympic mountains
Fig. 3.30
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How old is the seafloor?
Fig. 3.19
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What’s happening along our coast?
Under our feet?
Seattle earthquake and fault http://www.youtube.com/watc
h?v=V0WuSCaTYI0
Fig. 3.29
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What’s happening along our coast?
Under our feet?
 Juan de Fuca Plate spreading
away from ridge and under North
American Plate
 Pacific plate spreading away from
other side
 Have all three types of plate
boundaries
 At divergent boundary of Juan de
Fuca Ridge, there are
hydrothermal vents
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Hydrothermal vents – Black Smokers
 Hydrothermal vents are geysers on the seafloor
 Discovery: http://www.youtube.com/watch?v=D69hGvCsWgA (Bob Ballard)
 Black smokers http://www.bbc.co.uk/nature/habitats/Hydrothermal_vent#p00fff1y
(David Attenborough)
 Lost City: http://www.youtube.com/watch?v=Xfzbvd33Opc (Bob Ballard)
 Form along Mid-Ocean Ridges
 Hot or molten rock (magma) beneath the ocean floor drives hydrothermal vents
 Vents can occur at any depth
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Vents (Black Smoker) Around the
World
 Location of known black smoker hydrothermal vents
 Color coding shows like biological communities
 Black smokers are found only in areas where there is volcanic
activity and the magma is close enough to the surface to heat
the fluids
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How are black smokers formed?
 Water seeps through
cracks in the seafloor
and is heated by
near-magma
interaction – minerals
dissolved in fluid
 Hot, mineral rich fluid
rises to the surface
and gushes out of the
vent openings - exits
between 20°-400°C
 Dissolved metals and
other chemicals
precipitate out to
form “chimneys” of
new rock
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Vent Biology – Black Smokers
 How do living things survive in such an environment?
 Bacteria
 What energy source do they use?
 Water coming out of a vent is rich in dissolved minerals
 Sulfur compounds (hydrogen sulfide)
 Bacteria use dissolved minerals to produce organic material
through the process of chemosynthesis
 Bacteria are autotrophs
 Chemosynthetic bacteria are the primary producers and form
the base of vent food webs - all vent animals ultimately depend
on the bacteria for food
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Chemosynthesis
 Chemosynthesis is the biological conversion of one or more
carbon molecules (usually carbon dioxide or methane) and
nutrients into organic matter using inorganic molecules (e.g.
hydrogen gas, hydrogen sulfide) or methane as a source of
energy, rather than sunlight, as in photosynthesis
 Hydrogen sulfide chemosynthesis:
CO2 + O2 + 4H2S → CH2O + 4S + 3H2O
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Vent Biology – Black Smokers
 Bacteria live in
 Pores and on rock
 Animal guts
 Chemosynthetic bacteria grow into a thick mat
 Mat attracts other organisms such as amphipods and copepods which graze
upon the bacteria directly
 Larger organisms such as anemones, snails, clams, mussels, shrimp, crabs,
tube worms, fish, and octopuses form a food chain of predator and prey
relationships above the primary consumers
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Tube Worms
 Tube worms grow in large clusters around the
vents and live inside hard, shell-like protective
tubes that attach to the rocks
 Grow to be 8 feet
 Lack mouths, anuses, intestines and stomachs
 How and what do they eat?
 Symbiotic relationship chemosynthetic
bacteria
 Insides are lined with bacteria that oxidize the
H2S, turning it into usable nutrients for the worms
 Bacteria, in turn, benefit from the relationship
because the worms deliver blood-containing
hemoglobin, which helps the bacteria to break
down the sulfides
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Giant Vent Clam
 Can grow as
large 1-1.5 feet
 No gut or functional digestive
system
 Symbiotic bacteria
 Fix carbon, fix nitrogen and
produce amino acids, vitamins
and other nutrients required by
the clam
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“Lost City” – a new vent-type
 Discovered in December 2000 in mid-Atlantic Ocean
 Atlantis Massif – NOT near magma
 Heat from reactions between seawater and upper mantle rocks (peridotite)
 Methane- and hydrogen-rich fluids
 Highly alkaline (pH 9 to 11)
 Temperatures ranging from 40° to 90° C
http://www.youtube.com
/watch?v=Xfzbvd33Opc
 Microbes and small invertebrates associated
 Field of about 30 chimneys made of calcium carbonate 30 to 60 meters tall,
with a number of smaller chimneys
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Test your knowledge
 Can you describe what causes an earthquake and explain why the Pacific NW
is susceptible to a big shake in the future?
 Can you describe how the continents move and identify the source of
heat/energy that drive plate tectonics?
 Can you define what convection currents are and explain the process that
creates them?
 Can you identify the three types of plate boundaries and the seafloor features
associated with each type (Figs. 3.22-3.30)?
 Can you identify sites of seafloor creation, and the relative age of ocean crust
(Fig. 3.9 & 3.19)?
 Can you describe the geologic processes that form(ed) Washington state?
 Can you explain how hydrothermal vents are formed and locate on a map
where hydrothermal vents are likely to be found?
 Can you explain how life at hydrothermal vents differs from life in the surface
ocean?
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