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Famous project



formation of volcanic layer- a case study-> FAMOUS Project ( French-American Mid-Ocean Undersea Study).

formation of volcanic layer- a case study-> FAMOUS Project ( French-American Mid-Ocean Undersea Study).



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Famous project Presentation Transcript

  • 2.  Classic survey of part of the Mid-Atlantic Ridge in 1970s. Provide understanding in pattern of volcanism, fissuring, rifting anddykes injection that occur along ocean ridge axes. Start in 1971. As theory of sea floor spreading and plate tectonic beingaccepted. Right time plate are generate ( oceanic ridge). Area of study: Small segment of Mid-Atlantic Ridge, southwest Azores. Boundary between African and American plate. Reason this area chosen: Aeromagnetic survey show clear central magnetic anomaly. Not far from port of Ponta Delgada . A series of bathymetric survey carried out to produce maps. On maps (Figure 4.5), transform fault can be seen. Figure 4.6Inner rift floor is 2.5km depth and contain small hillssuch as Mount Venus and Mount Pluto.
  • 3. TECHNIQUE. Almost every marine geological and geophysicalwas used. Many technique not for marine studies and had tobe modified for FAMOUS project.
  • 4. NAVIGATION SYSTEM. High precision required cause navigation problembecome acute. Solved by: By develop acoustic navigation system. Used acoustic transponder placed on sea floor andlinked to ship and submersible. Equipment proved adaptable. Can be used with other instrument packages thattowed near sea-floor.
  • 5. SIDE-SCAN SONAR. GLORIA is a side-scan echo-sounding system contribute byBritish. Gave image of sea-floor topography. The topography photo is built up by mosaic the records. For FAMOUS, side-scan sonar mosaic obtained bycombine overlapping sonographs. Useful for: Identify the major fault scarp. Determine the limit extent of fracture zone .
  • 6. LIBEC(LIGHT BEHIND CAMERA SYSTEM). Overcome field of view (FOV) andunderwater photo quality that cause bylimited light scattering. High intensity LIBEC towed above sea floorand give large area photo. By taking many photo in rapid succession proved possible to build photomosaic ofsea-floor.
  • 7. The LIBEC system shot 120-foot-wide sections of the seafloor thatwere pieced together. (Courtesy ofU.S. Naval Research Laboratory)Project FAMOUS used the U.S.Navy’s LIBEC camera system, whichsuspended high-intensity electronicflash lamps well above the oceanbottom.
  • 8. NARROW-BEAM ECHO –SOUNDER.. Conventional echo-sounder beam width about 30º. Inadequate as the resolution more than 1km. Using US navy system (ALVIN) with beam width 2º. Much smaller object can be detect. Give submersible preparation guide. System have same FOV with submersible. Ease the manned submersible survey. Submersible designed with titanium hull for it workunder high pressure. Various sampling devices added: One arm manipulator pick specimen. Bag to collect loose sediment.
  • 9. AlvinFrench submersible Cyana
  • 10. INTERPRETATION OF FAMOUSDATA…Assumption… The features on the topographic map is the result ofvolcanism. Thus, each hill-like feature should have volcanicvents at or near the top and flow direction radiatingfrom it.
  • 11. EVOLUTION OF THE RIFT-VALLEYFLOOR… Figure 4.15 and 4.16 shows the successive stagesin the formation of 2 – 3 km wide strips of newoceanic crust either side of the Mid-Atlantic Ridgeduring the last 200,000 years. The process are consistent with a (half) spreadingrate of 1 - 2cm per year.
  • 12. EVOLUTION OF THE RIFT-VALLEYFLOOR… The frequency of volcanic events variesappreciably. By the time it was built up, eachvolcano would be underlain by a swarm of dykesemanating from the magma chamber beneath. Subsided and rifting process occurred. Rifts mostlyform beside either to the east or the west of eachvolcano. Each new phase of volcano-buildingdevelops about the latest rift. New volcanoes willtake up space so the older volcanoes are moveaside to accommodate them.
  • 13. EVOLUTION OF THE RIFT-VALLEYFLOOR… About 100,000 years old, the volcanic hills aresufficiently far from the axis to be uplifted by faultswhich mostly dip inwards from the walls. After 200,000 years, the volcanoes heave beenupfaulted completely out of the valley floor to thetops of the walls.
  • 14. PLAYThank you…