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PLATE TECTONICS. Earth made of concentric spheres ( Fig. 1.14 ) p 18 T-14. 1. Inner core - rich in iron and nickel, dense 2. Outer core - liquid 3. Mantle Asthenosphere - nearly molten and can flow very slowly

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Earth made of concentric spheres fig 1 14 p 18 t 14
Earth made of concentric spheres (Fig. 1.14) p 18 T-14

  • 1. Inner core - rich in iron and nickel, dense

  • 2. Outer core - liquid

  • 3. Mantle

    • Asthenosphere - nearly molten and can flow very slowly

    • Lithosphere - rigid outer layer of the earth and floats in the asthenosphere. (Fig. 1.16) p 22 T-29 S&A-22


  • 4. Crust

    • basalt (fine grained igneous rock, volcanic)

  • 5. Hydrosphere

  • 6. Atmosphere


Earth made of concentric spheres review
Earth made of concentric spheres review

  • 1. Inner core

  • 2. Outer core

  • 3. Mantle

    • Asthenosphere

    • Lithosphere

  • 4. Crust

  • 5. Hydrosphere

  • 6. Atmosphere


Isostasy
Isostasy

  • Isostatic adjustment

  • describes the relative elevations that materials of different densities and thicknesses reach at equilibrium with gravity (1.16) p 20 S&A 23T-20

  • Play the game of isostasy before class!


Isostasy cont
Isostasy cont

  • Crustal materials float in asthenosphere (Fig. 14) p 20

  • Weight of volcano bends crust (Fig 2.27) remember from last time.

  • Glaciers also cause crust so subside (a process by which one plate descends beneath another plate and is ultimately resorbed into the mantle)


Isostasy cont1
Isostasy cont

  • Scandinavia and Antarctica are rising due to the melting of the glaciers that cover them.

  • Remember how the block raised when we reduced the height (from isostasy game).



Moho exposed at the surface located between crust and mantle s a 22
MOHO exposed at the surface Mohorovicic discontinuity, between Earth's brittle outer crust and its hotter, softer mantle located between crust and mantle (S&A 22)


Continents
Continents Mohorovicic discontinuity, between Earth's brittle outer crust and its hotter, softer mantle

  • Thick accumulations of granitic rocks

  • Oldest rocks on Earth - about 3.8 billion years


Plate tectonics1
Plate tectonics Mohorovicic discontinuity, between Earth's brittle outer crust and its hotter, softer mantle

  • New crust formed at mid-ocean ridges or spreading centers Convection currents (Fig. 2.10) p 44 (this is a very important diagram)

  • Crust and upper mantle constitute the rigid lithosphere float on nearly molten asthenosphere


Plate tectonics cont
Plate tectonics cont Mohorovicic discontinuity, between Earth's brittle outer crust and its hotter, softer mantle

  • Lithosphere broken into rigid units and move slowly older lithospheric material is being subducted while new lithosphere is produced along the ridges and rises.

  • Trenches plates converge

  • Plates move past each other along transform faults (Fig. 2.23) p 59

  • Plate movements shape ocean basins T-30 (Fig. 2.13 b) p 48


Plate boundaries fig 2 14 a b c p50
Plate boundaries ( Mohorovicic discontinuity, between Earth's brittle outer crust and its hotter, softer mantle Fig. 2.14 a. b. c.) p50

  • 1. Divergent boundary - Midocean ridges - plates form and move away from each other (Fig. 2.14 a)

  • 2. Convergent boundary - Trenches - plates move toward each other and are destroyed as they are drawn down into the mantle (subduction) (Fig. 2.14 b, 2.20, 2.21, and 2.22) p 56-58


Plate boundaries cont
Plate boundaries cont. Mohorovicic discontinuity, between Earth's brittle outer crust and its hotter, softer mantle

  • 3. Fracture zones - plates slide past each other (NO earthquakes felt)

  • 4. Transform faults - plates slide past each other (Earthquakes felt) (Fig. 2.14 c)

  • Transform faults and fracture zones (Fig. 3.17) p 95 (T 38)

  • San Andreas Fault (Fig. 2.23) p 59


Continental rifting fig 2 17 p 52
Continental Rifting Mohorovicic discontinuity, between Earth's brittle outer crust and its hotter, softer mantle Fig 2.17 p 52

  • a. upwarping

  • b. rift valley (fig 2.18) p 54 read and understand

  • c. linear sea

  • d. mid-ocean ridge

  • e. Table 2.1 p 51



  • START HERE FOR WEDNESDAY Submarine Ring of Fire 2002 Exploration, NOAA-OE.

  • If you are interested in a 9th edition of our book.

  • [email protected]


I want you to print out an article on hot spots
I want you to print out an article on hot spots Submarine Ring of Fire 2002 Exploration, NOAA-OE.

  • Go to google and look up hot spots.


Hot spots
Hot spots Submarine Ring of Fire 2002 Exploration, NOAA-OE.

  • plumes of magma that rise from deep within the mantle erupt (Fig. 2.24) p 62 T 54

  • Plates moving across hot spots cause chains of volcanic islands Hawaiian Islands (Fig. 2.25) p 62

  • Many occur near midocean ridges. Seen today in Iceland. (Fig2.26) p 63 formation of sea mounts and table mounts (guyots)



Hot spots cont
Hot spots cont. islands Hawaiian Islands

  • Others beneath the continent - gisers in Yellowstone National Park

  • Flood Basalts - from volcanic activity that produces widespread gently sloping surfaces. Commonly surround volcanic islands


Earth s magnetic field
Earth’s magnetic field islands Hawaiian Islands

  • Fig 2.7 and 2.9 p 40 and 43


Earth s magnetic field fig 2 12 p 46 t 28
Earth's magnetic field ( islands Hawaiian IslandsFig. 2.12) p 46 T 28

  • Changes orientation at irregular intervals, as of today we do not know why.

  • Minerals record the orientation of Earth's magnetic field at the time when the rocks cooled ~ 100,000 yrs (Fig. 2.11) p 45

  • Measure with magnetometers T 48


Earth s magnetic field cont
Earth's magnetic field cont islands Hawaiian Islands.

  • Form bands with same orientation - like tape recorder T-26

  • Matthews and Vine saw the magnetized rocks and decided that the rocks were younger in the center of the ridge, older at edges

    • Permits determining age of ocean floor


Neat stuff on the earths magnetic field
Neat stuff on the earths magnetic field islands Hawaiian Islands

  • http://science.nasa.gov/headlines/y2003/29dec_magneticfield.htm

  • www.pbs.org/wgbh/nova/magnetic/reversals.html

    • This shows an interactive. I expect you to do this


Hydrothermal circulation p 93
Hydrothermal circulation p 93 islands Hawaiian Islands

  • Sea water circulates through hot, newly formed rocks (Fig 3.17 a) p 93

    • 1. cooling them

    • 2. removes metals and deposits them in ocean floor vents

    • 3. ocean water circulates through newly formed crust every 5 - 10 million years. (remember the ocean has been around a very long time)



Three types of hydrothermal vents p 94
Three types of hydrothermal vents p 94 spreading segment than on slow spreading ones.

  • black smokers

  • white smokers

  • cooler discharge


Black smokers
black smokers spreading segment than on slow spreading ones.


White smoker
White smoker spreading segment than on slow spreading ones.


Hydrothermal vents cont
Hydrothermal Vents spreading segment than on slow spreading ones.cont.

  • Three types of hydrothermal vents

    • 1. most spectacular are black smokers.

      • a. They discharge superheated waters (300 - 400oC) at high rates much like a fire hose.

      • b. Black because of chem. rx. 2o to those that occur in the water forming sulfur-bearing minerals.

      • c. form large fragile chimney like mounds up to 10 meters high made of porous silica, native sulfur, and sulfur-bearing minerals.


Hydrothermal vents cont1
Hydrothermal Vents spreading segment than on slow spreading ones.cont.

  • d. Color the mounds with yellows and blacks (like Halloween decorations) Read Recovery of Black Smokers p 90-91

  • e. Tube worms: Very fast growing and reach sizes up to 3 m (10 ft) other animals include sea anemone, clams, crabs, fish and bacteria Fig 15.25 p 477

  • f. Temperature fluctuations are common occurring in days to seconds.

  • g. Micro-organisms


Tube worms t 134
Tube worms spreading segment than on slow spreading ones.T 134


Hydrothermal vents cont2
Hydrothermal Vents spreading segment than on slow spreading ones.cont.

  • 2. White smokers

    • a, are not as hot (200-330 oC) are also common

    • b. circulating fluids have mixed with cold ocean waters

    • c. milky discharge thus the name


Hydrothermal vents cont3
Hydrothermal Vents spreading segment than on slow spreading ones.cont.

  • 3. Cooler discharge (cold seep) (5 - 25oC)

    • a. water flows out through cracks and fissures in the ocean floor.

    • b. cold seep waters are about the same temperature as the surrounding waters

    • c. the discharge water is clear


Hydrothermal vents cont4
Hydrothermal Vents spreading segment than on slow spreading ones.cont.

Hydrothermal circulation continues for millions of years as the rocks cool.

  • Eventually, fractures fill with mineral deposits and fluids no longer pass through.

  • Sediments accumulate on the ocean floor.

  • Where do the minerals come from?


All three vents support abundant growths of bottom dwelling organisms
All three vents support abundant growths of bottom-dwelling organisms.

  • Chemosynthesis: the process by which certain microbes create energy by mediating chemical reactions


Continental margins
Continental Margins organisms.

  • (steep slopes that descend to the sea floor) p 100 - 102

  • One of the most outstanding features of the continental slopes are submarine canyons. (Fig 3.9 p 83) Submarine canyons are steep sided and V-shaped in cross section with tributaries similar to those of river-cut canyons.


Continental margins two types fig 3 7 p 82
Continental Margins two types organisms.(Fig 3.7) p 82

  • 1. Active continental margins lie along edge of plates (Convergent)

    • Contain many active volcanoes, frequent earthquakes, young mountains

    • Common along Pacific margins, called Pacific-type margins are frequently narrow

  • 2. Passive margins of continents lie in middle of plates


Active margins
ACTIVE MARGINS organisms.


Earthquakes
Earthquakes: organisms.

  • 1. common near Pacific-type margins

  • 2. deep earthquakes indicate subduction - in subduction zones, plates move as large slabs and drag against the rocks above and below causing earthquakes in those areas

  • 3. subduction causes a drag on rocks -> deform the rocks along the margins -> energy buildup -> earthquakes -> energy releases


Subducting plate is old and dense
Subducting plate is organisms.old and dense -

  • it sinks into the mantle as a steeply dipping slab


Subducting plate is young
Subducting plate is organisms.young

  • still warm, and relatively buoyant

  • slab dips at a shallow angle

  • occurs along the eastern margin of the Pacific, where the American plate is overriding recently formed crust

  • volcanoes occur on land

  • many of earthquakes


Exotic terranes
Exotic terranes organisms.

  • terranes have a history distinct from adjoining crustal fragments are welded onto continents during subduction (A&S-41)



Passive margins

PASSIVE MARGINS organisms.


Passive margins of continents
Passive margins of continents organisms.

  • No earthquakes, no volcanoes. Fig 3.7 p 81 book

  • Called Atlantic-type margins

  • Form after continents are rifted apart and tend to be wide

  • Thick sediment deposits and old oceanic crust

    • trenches do not form,

    • sediment is folded into mountain ranges (Appalachians, Alps, Himalayas, and Urals)


Passive margins cont
Passive margins cont. organisms.

  • Economically, they are important because of the accumulations of oil and gas that they often contain. Most of the world's giant oil and gas fields occur in such deposits.

  • Found on Atlantic Ocean, Antarctic Ocean. Arctic Ocean, and Indian Ocean


Mantle convection fig 2 10 p 44
Mantle convection ( organisms.Fig 2.10 p 44)

  • Occurs in mantle, causing plate movements

  • Supplies molten rock to midocean ridges, causing volcanism

  • 1. hot-spot volcanoes originate at unusually hot areas of the core mantle boundary

  • 2. the overlying mantle melts, forming plumes of magma that rise and penetrate the crust as volcanoes.


Mantle convection cont
Mantle convection cont. organisms.

  • 3. these hot spots do not move with the overlying mantle and thus remain fixed in location for tens of millions of years

  • 4. red patches - continental flood basalts and oceanic lava plateaus T 54

  • Crust cools as it ages, and grows denser

  • Oldest, densest rock sinks into the mantle at the trenches


Formation of ocean basins fig 2 17 abcd
Formation of ocean basins ( organisms.Fig 2.17 abcd)

  • Formed through the breakup of continents. Begins when a continent remains in one location for >100 million years continent impedes heat flow from the earth's interior.


Formation of ocean basins cont
Formation of ocean basins cont organisms.

  • a. underlying mantle heats, expanding and uplifting the overlying lithosphere

  • b. continents rift, forming narrow valleys (rift valley in Africa)

  • c. valleys widen into narrow ocean basin, e.g., Red Sea midocean ridges in the middle of ocean - actively widening

  • d. ocean continues to widen until the oldest crust becomes dense enough to sink, causing the ocean to gradually narrow


Destruction of ocean basins fig 2 20 abc p 56
Destruction of ocean basins organisms.Fig 2.20 abc p 56

  • Ocean - continent convergence

  • Ocean - ocean convergence

  • Continent - continent convergence

  • Mountains form when basin closes

  • Appalachian Mountains mark site of ancient ocean that closed about 400 million years ago Can see the sedimentary rocks on the AT



Mantle convection fig 2 10 p 441
Mantle convection ( organisms.Fig 2.10 p 44)

  • Occurs in mantle, causing plate movements

  • Supplies molten rock to midocean ridges, causing volcanism

  • 1. hot-spot volcanoes originate at unusually hot areas of the core mantle boundary

  • 2. the overlying mantle melts, forming plumes of magma that rise and penetrate the crust as volcanoes.


  • 3. these hot spots do not move with the overlying mantle and thus remain fixed in location for tens of millions of years

  • 4. red patches - continental flood basalts and oceanic lava plateaus T 54

  • Crust cools as it ages, and grows denser

  • Oldest, densest rock sinks into the mantle at the trenches


Boundaries table 2 2 p 53
Boundaries and thus remain fixed in location for tens of millions of yearsTable 2.2 p 53

  • a. divergent - plates move apart

  • b. convergent - plates collide

  • c. transform - plates slide past one another

  • d. Study this table (It is on this exam)


Points to remember
Points to remember and thus remain fixed in location for tens of millions of years

  • Continent - from granite

  • Ocean - from basalt

  • Heat flow - Fig 2.10 p 44

  • Table 2.1 p 51 This is the culture vulture question


Breakup of pangaea on to present
Breakup of Pangaea on to present and thus remain fixed in location for tens of millions of years

  • Began about 225 million years ago, with the breakup of Pangaea about 180 million years ago T 21 - 23 and 15

  • North Atlantic formed first, South Atlantic later

  • Indian Ocean is the youngest basin

  • Pacific is the remnant of Panthallasia, previous cycle


Present spreading cycle cont
Present spreading cycle and thus remain fixed in location for tens of millions of yearscont.

  • Mediterranean is the remnant of Thetys Sea


End plate tectonics

END Plate Tectonics and thus remain fixed in location for tens of millions of years

We have seen all the material that will be covered on Exam I


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