 Here's a rap about plate boundaries that get's stuck in my head all the time:   This is how our continents have moved around over time due to plate tectonics- with dramatic music!   And lastly, because I think it is super cool to see, here is India colliding with Asia to form the Tibetan plateau and Himalayas:  1

Announcements  TA evaluations   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 10 th 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 2

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  Must ask for and attach admission receipt to get full credit for assignment 3 Located on the corner of 17th Ave NE and NE 45th Street

It’s not a question of if, but when… …predicting the next big earthquake. Earthquakes, volcanoes, tsunamis…oh my…  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? 4

It’s a question of when Nisqually Quake: Simulation of Viaduct CollapseSimulation of Viaduct Collapse: http://link.brightcove.com/services/player/bcpid ?bctid=

What do you notice? What do you wonder? Fig. 3.8 First physiographic chart of the seafloor 6 Fig – Earthquake epicenters

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  earthquakes/ 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 7

The planet is layered, like a giant hard boiled egg  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 Fig

Earth’s interior  Lithosphere is formed by the fusion of crust and mantle  Strong, rigid surface shell (plates)  Rides on top of asthenosphere which is weak, partially molten and deformable (due to pressure and temperature) Fig

Cracked egg - tectonic plates 10

Plates are constantly moving and changing Fig

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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  Slab pull  Subduction of dense materials pulls plates apart  Destruction of crust 16 Fig. 3.9

Three Types of Plate Boundaries 17

Transform fault boundary  The zone between two plates sliding horizontally past one another is called a transform-fault boundary  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  Crust is not created or destroyed 18

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  What features are associated with divergent boundaries?  Hydrothermal vents  Seamounts (usually extinct volcanoes)  Earthquakes Fig

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? 20

Convergent boundaries  Two plates crashing together is known as a convergent boundary  Occurs at ocean-ocean, ocean-continental and continental-continental margins  One plate sinks or subducts under the other plate  Which plate sinks?  Densest  Which one is the densest? Fig

Ocean-continental convergence  Which plate subducts?  Denser plate  Oceanic  What features are associated with ocean- continental convergence?  Volcanoes (Cascade Mountains)  Trenches form  Usually parallel to continent  Do we see one along our coast?  Earthquakes Fig That’s what our own convergent boundary does! 22

Oceanic-oceanic convergence  Plate with edge furthest from spreading center is subducted  Oldest plate subducts  What features are associated with ocean-ocean convergence  Trench  Volcanoes (island arc)  Earthquakes Fig

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

How old is the seafloor? Fig

Fig What’s happening along our coast? Under our feet? Seattle earthquake and fault - h?v=V0WuSCaTYI0 26

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 27

Hydrothermal vents – Black Smokers  Hydrothermal vents are geysers on the seafloor  Discovery: (Bob Ballard)  Black smokers (David Attenborough)  Lost City: (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 28

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 29

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 30

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 31

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: CO 2 + O 2 + 4H 2 S → CH 2 O + 4S + 3H 2 O 32

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 33

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 H 2 S, 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 34

Giant Vent Clam 35  No gut or functional digestive system  Symbiotic bacteria  Fix carbon, fix nitrogen and produce amino acids, vitamins and other nutrients required by the clam  Can grow as large feet

“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  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 /watch?v=Xfzbvd33Opc 36

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 )?  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? 37