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

1. FAMOUS PROJECT
( FRENCH-AMERICAN MID-OCEAN
UNDERSEA STUDY).
James R. Heirtzler
was the U.S. leader
of Project FAMOUS.

2.  Classic survey of part of the Mid-Atlantic Ridge in 1970s.
 Provide understanding in pattern of volcanism, fissuring, rifting and
dykes injection that occur along ocean ridge axes.
 Start in 1971.
 As theory of sea floor spreading and plate tectonic being
accepted.
 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 hills
such as Mount Venus and Mount Pluto.

3. TECHNIQUE.
 Almost every marine geological and geophysical
was used.
 Many technique not for marine studies and had to
be modified for FAMOUS project.

4. NAVIGATION SYSTEM.
 High precision required cause navigation problem
become acute.
 Solved by:
 By develop acoustic navigation system.
 Used acoustic transponder placed on sea floor and
linked to ship and submersible.
 Equipment proved adaptable.
 Can be used with other instrument packages that
towed near sea-floor.

5. SIDE-SCAN SONAR.
 GLORIA is a side-scan echo-sounding system contribute by
British.
 Gave image of sea-floor topography.
 The topography photo is built up by mosaic the records.
 For FAMOUS, side-scan sonar mosaic obtained by
combine 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) and
underwater photo quality that cause by
limited light scattering.
 High intensity LIBEC towed above sea floor
and give large area photo.
 By taking many photo in rapid succession 
proved possible to build photomosaic of
sea-floor.

7. The LIBEC system shot 120-foot-
wide sections of the seafloor that
were pieced together. (Courtesy of
U.S. Naval Research Laboratory)
Project FAMOUS used the U.S.
Navy’s LIBEC camera system, which
suspended high-intensity electronic
flash lamps well above the ocean
bottom.

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 work
under high pressure.
 Various sampling devices added:
 One arm manipulator pick specimen.
 Bag to collect loose sediment.

9. Alvin
French submersible Cyana

10. INTERPRETATION OF FAMOUS
DATA…
Assumption…
 The features on the topographic map is the result of
volcanism.
 Thus, each hill-like feature should have volcanic
vents at or near the top and flow direction radiating
from it.

11. EVOLUTION OF THE RIFT-VALLEY
FLOOR…
 Figure 4.15 and 4.16 shows the successive stages
in the formation of 2 – 3 km wide strips of new
oceanic crust either side of the Mid-Atlantic Ridge
during the last 200,000 years.
 The process are consistent with a (half) spreading
rate of 1 - 2cm per year.

12. EVOLUTION OF THE RIFT-VALLEY
FLOOR…
 The frequency of volcanic events varies
appreciably. By the time it was built up, each
volcano would be underlain by a swarm of dykes
emanating from the magma chamber beneath.
 Subsided and rifting process occurred. Rifts mostly
form beside either to the east or the west of each
volcano. Each new phase of volcano-building
develops about the latest rift. New volcanoes will
take up space so the older volcanoes are move
aside to accommodate them.

13. EVOLUTION OF THE RIFT-VALLEY
FLOOR…
 About 100,000 years old, the volcanic hills are
sufficiently far from the axis to be uplifted by faults
which mostly dip inwards from the walls.
 After 200,000 years, the volcanoes heave been
upfaulted completely out of the valley floor to the
tops of the walls.

14. PLAY
Thank you…