非常好的-板塊漂移學(xué)說(shuō)

1、Brushing up on basic geography will help you learn Plate TectonicsOnce you know your basic geography (continents and major mountain ranges) and ocean basin features (Mid Ocean Ridges, Oceanic Trenches) you can-Learn the 7 major plates-Learn the types of plate boundaries-Learn why those features are

2、where they are E. Forces shaping the Earth at the surface and from within 1. Surficial Processes Solar energy and gravity shaping the landscape 2. Internal Processes Internal energy and forces that buckle and break Earths crust Question: If 550 million tons of rock are broken down and transported to

3、 the sea from the United States each year, Why has our continent not been worn flat after the billions of years of its existence and Why havent the oceans been filled in?Mississippi River DeltaMississippi River Drainage BasinErosion, transport, depositionMississippi River Delta Weathering Chemical a

4、nd Mechanical Breakdown of solid rock into sediments Erosion Removal of rock and sediment from source by Gravity, wind, water, ice Transport over large distances by water, wind and ice. Deposition of large amounts of sediment in seas and oceans2. Internal Earth Processes Results of the “Internal Hea

5、t Engine” Evidence of internal energy and forces working on our earth. Intricate landscapes Volcanoes Earthquakes Geothermal Gradients (deeper is hotter)Another Question: What is the source of all this energy?3. Formation of Earth/projects/planets/planets.html Birth of the Solar Sys

6、tem Nebular Theory nebula compresses Flattening of spinning nebula and collapse into center to form sun Condensation to form planets, planetesimal, moons and asteroids during planetary accretion around 4 billion years ago (Meteorites are iron-rich and rocky fragments left over from planetary accreti

7、on)/projects/planets//kaufman/ppt/chapter4/sld002.htmOrion NFormation of the Planets The mass of the center of the solar system began nuclear fusion to ignite the sun The inner planets were hotter and gas was driven away leaving the terre

8、strial planets The outer planets were cooler and more massive so they collected and retained the gasses hence the “Gas Giants”Gas GiantsTerrestrial Planets /rose/backgrounds.htmlDifferentiation of the Planets The relatively uniform iron-rich proto planets began to separate into zones of

9、different composition: 4.6mya Heat from impacts, pressure and radioactive elements cause iron (and other heavier elements) to melt and sink to the center of the terrestrial planetsThe zones of the earths interiorFurther Differentiation of Earth Lighter elements such as Oxygen, Silicon, and Aluminum

10、rose to form a crust The crust, which was originally thin and heavy (iron rich silicate) Like todays Oceanic crust, Further differentiated to form continental crust which was thicker, iron poor and lighter Figure 1.7, the zones of the earths interiorComposition of Earth and Crust Element(Atomic #) C

11、hemical Symbol % of Earth% of Crust(by Weight)Change in Crust Due to DifferentiationOxygen (8)O3046.6IncreaseSilicon (14)Si1527.7Increase Aluminum (13)Al18.1Increase Iron (26)Fe355.0Decrease Calcium (20)Ca13.6Increase Sodium (11)Na12.8Increase Potassium (19)K12.6Increase Magnesium (12)Mg102.1Decreas

12、e All Others 81.5 Crust and MantleLithosphere and Asthenosphere The uppermost mantle and crust are rigid solid rock (Lithosphere) The rest of the mantle is soft but solid (Asthenosphere) The Continental Crust “floats” on the uppermost mantle The denser, thinner Oceanic Crust comprises the ocean basi

13、nsFigure 1.7, Detail of crust and Mantle The Lithosphere is broken into “plates” (7 major, 6 or 7 minor, many tiny) Plates that “ride around” on the flowing Asthenosphere Carrying the continents and causing continental driftLitho-spheric PlatesPlates Shown by PhysiographyTypes of Plate Boundaries -C

14、onvergent -Divergent -TransformLithospheric Plates and Boundary typesThree Types of Plate Boundaries Divergent | Convergent | Transforme.g., Pacific NW Where plates move away from each other the iron-rich, silica-poor mantle partially melts and Divergent Plate BoundariesAsthenosphereLithosphereLitho

15、sphereSimplified Block Diagram Extrudes on to the ocean floor or continental crust Cool and solidify to form Basalt: Iron-Rich, Silica-Poor, Dense Dark, Fine-grained, Igneous RockCharacteristics of Divergent Plate BoundariesOceanicCrustMagma Generation Divergent Plate Boundary Stress: Tensional exte

16、nsional strain Volcanism: non-explosive, fissure eruptions, basalt floods Earthquakes: Shallow, weak Rocks: Basalt Features: Ridge, rift, fissures Locations of Divergent Plate BoundariesMid-Ocean Ridges East Pacific Rise Mid Atlantic Ridge Mid Indian Ridge Mid Arctic RidgeFig. 1.10(Mid-Arctic Ridge)

17、East Pacific RiseMid-Atlantic RidgeIndianRidgeMid-03070150300500Divergent Plate BoundariesRifting and generation of shallow earthquakes (33km)Depth(km)03370 300 150 500 800 Fig. 19.21 Fig. 19.22Rift ValleyPassive continental shelf and riseRift ValleyE.g., Red Sea and East African Rift ValleysThinnin

18、g crust, basalt floods, long lakesShallowEarthquakesLinear sea, uplifted and faulted marginsOceanic CrustFig. 2-15Pg. 40Fig. 2-16Pg. 41Convergent Plate Boundaries Where plates move toward each other, oceanic crust and the underlying lithosphere is subducted beneath the other plate (with either ocean

19、ic crust or continental crust) Wet crust is partially melted to form silicic (Silica-rich, iron-poor, i.e., granitic) magma Stress: Compression Earthquakes Volcanism Rocks Features LithosphereSimplified Block DiagramAsthenosphereSubducted PlateOceanic TrenchPlate MovementMagma GenerationVolcanic Arc

20、Shallow and Deep EarthquakesLithosphereFig. 2-17Pg. 42Convergent Plate Boundary e.g., Pacific Northwest Volcanic Activity Explosive, Composite Volcanoes (e.g., Mt. St. Helens) Arc-shaped mountain ranges Strong Earthquakes Shallow near trench Shallow and Deep over subduction zone Rocks Formed Granite

21、 (or Silicic) Iron-poor, Silica-rich Less dense, light colored Usually intrusive: Cooled slowly, deep down, to form large crystals and course grained rockFig. 2-18Pg. 42Composite Volcanic Arcs (Granitic, Explosive)Basaltic Volcanism (Non-Explosive)The “Ring of Fire” (e.g., current volcanic activity)

22、A ring of convergent plate boundaries on the Pacific RimNew Zealand Tonga/SamoaPhilippinesJapanese Isls.Aleutian Island arc and TrenchCascade RangeSierra MadreAndes Mtns. Also: Himalayans to the Alps Indonesia Fujiyama East Pacific Rise PinatuboAndes MountainsCascade Range AleutianIsland Arc Siarra

23、Madre Japanese Isls. New Zealand Phillipines. Depth of Earthquakes at convergent plate boundariesSeismicity of the Pacific Rim 1975-199503370 300 150 500 800 Shallow quakes at the oceanic trench (70 km)Depth(km)Each major plate caries a continent except the Pacific Plate.Each ocean has a mid-ocean r

24、idge including the Arctic Ocean.Divergent bounds beneath E. Africa, gulf of CaliforniaThe Pacific Ocean is surrounded by convergent boundaries. Also Himalayans to the AplsMajor Plates and Boundaries Iceland Kilimanjaro RedSeaGulf of Aden Etna Visuvius East African RiftMid-Atlantic RidgeMid-Indian Ri

25、dgeDivergent Plate BoundariesRifting and Formation of new Basiltic Oceanic CrustOceanic Crust* Thin (10 km) Young (5%) / Silica Poor (50%) Dense ( 3 g/cm3) Low lying (5-11 km deep) Formed at Divergent Plate BoundariesComposite Volcanic Arcs (explosive)Basaltic Volcanism (non-explosive)*Make a “Compa

26、rison Table” on a separate pageConvergent Plate BoundariesFormation of Granitic Continental CrustContinental Crust Thick (10-50 km) Old (200 m.y. and up to 3.5 b.y.) Iron Poor (70%) Less Dense ( 2.5 g/cm3) High Rising (mostly above see level) Formed at Convergent Plate BoundariesOceanic Crust Thin (

27、10 km) Young (200 my) Iron Rich (5%) / Silica Poor (50%) Dense (s.g. 3 x H2O) Low lying (5-11 km deep) Formed at Divergent Plate BoundariesIsostatic Adjustment Why do we see, at the earths surface, Intrusive igneous rocks and Metamorphic rocks Formed many km deep? Thick, light continental crust buoy

28、s up even while it erodes Eventually, deep rocks are exposed at the earths surface Minerals not in equilibrium weathered (transformed) to clay Sediments are formed Transform Plate Boundaries Offset Mid- ocean ridges May cut continents e.g. San Andreas FaultFig. 2-21Pg. 44The Hydrologic Cycle Works with Plate-Tectonics to Shape the land Weatheringclay, silt, sand Erosion Transport Sedimentation Geologic Materials Sediments Sedimentary RocksThe 3 rock types form at convergent plate boundariesIgneous Rocks: When rocks melt, Magma is formed, rises, cools