an average depth of less than 3,000 m. Similarly to the area in the North, the
southern part of the MAR is also associated with disseminated islands having
hotspot origins.
(2) The other MAR provinces, between the Oceanographer fracture zone near
34850
0 N down to the Romanche fracture zone near 5°S, are associated with
magma-starved ridge segments. These zones are less affected by magmatic
activity and hence have a relatively thin crust. The average topography in the
Equatorial Atlantic is deeper than 3000 m and reaches up to 4,300 m. The
province with the coldest lithosphere and deepest topography is in the
Equatorial Atlantic between 3°N and 3°S. This is a site with significant lithosphere deformation and alteration where strike-slip transform movements
coupled with extensional motions occur. It is an area with the highest concentration of closely spaced fracture zones between the African and South
American continents. Some of these major offsets include the St. Peter and St.
Paul’s Rocks, the Chain and the Romanche transform faults (See Chap. 8)
(Fig. 7.2).
In summary, the North and the South Atlantic accreting plate boundary regions
are sites of more magma productivity due to the upwelling of hot convective cells
within the mantle giving rise to ridge centered hotspots. These hot mantle convective areas are separated by a stretch of colder lithosphere located in the magmastarved equatorial Atlantic region. Detailed studies of these different types of
spreading ridge segments were made by submersible during several sea-going
expeditions conducted between 1973 and 1998.
Two parts of the MAR that were particularly studied in detail are located in an
area near the Azores, also known as the ‘‘FAMOUS area’’ near 37°N and in the
OCEANAUT area located near 34°50
0 N on the ridge segment between the
Oceanographer and the Hayes fracture zone, which is also called the ‘‘Oceanographer area’’ (Fig. 7.2).
The FAMOUS project: The Mid-Atlantic Ridge near 37°N
The region of the MAR at 35–37°N has been offset by 13 different spreading ridge
axial segments with an average length of about 80 km. This part of the MAR ends
with a first order discontinuity called the Oceanographer Transform Fault near
358N (Fig. 7.2). One of the ridge segments, about 140 km long, is also the area
where the FAMOUS project took place. This segment is located west of the Azores
between 36858 and 36834
0 N at latitude 33816
0 W. The segment has a total
spreading rate of about 1.2 cm per year. The Franco-American Mid-Ocean
Undersea Survey project (FAMOUS) was designed to make detailed observations
on a diverging plate boundary where new crust was being created on a ridge
segment influenced by the Azores hotspot.
The Mid-Atlantic Ridge
171
southern part of the MAR is also associated with disseminated islands having
hotspot origins.
(2) The other MAR provinces, between the Oceanographer fracture zone near
34850
0 N down to the Romanche fracture zone near 5°S, are associated with
magma-starved ridge segments. These zones are less affected by magmatic
activity and hence have a relatively thin crust. The average topography in the
Equatorial Atlantic is deeper than 3000 m and reaches up to 4,300 m. The
province with the coldest lithosphere and deepest topography is in the
Equatorial Atlantic between 3°N and 3°S. This is a site with significant lithosphere deformation and alteration where strike-slip transform movements
coupled with extensional motions occur. It is an area with the highest concentration of closely spaced fracture zones between the African and South
American continents. Some of these major offsets include the St. Peter and St.
Paul’s Rocks, the Chain and the Romanche transform faults (See Chap. 8)
(Fig. 7.2).
In summary, the North and the South Atlantic accreting plate boundary regions
are sites of more magma productivity due to the upwelling of hot convective cells
within the mantle giving rise to ridge centered hotspots. These hot mantle convective areas are separated by a stretch of colder lithosphere located in the magmastarved equatorial Atlantic region. Detailed studies of these different types of
spreading ridge segments were made by submersible during several sea-going
expeditions conducted between 1973 and 1998.
Two parts of the MAR that were particularly studied in detail are located in an
area near the Azores, also known as the ‘‘FAMOUS area’’ near 37°N and in the
OCEANAUT area located near 34°50
0 N on the ridge segment between the
Oceanographer and the Hayes fracture zone, which is also called the ‘‘Oceanographer area’’ (Fig. 7.2).
The FAMOUS project: The Mid-Atlantic Ridge near 37°N
The region of the MAR at 35–37°N has been offset by 13 different spreading ridge
axial segments with an average length of about 80 km. This part of the MAR ends
with a first order discontinuity called the Oceanographer Transform Fault near
358N (Fig. 7.2). One of the ridge segments, about 140 km long, is also the area
where the FAMOUS project took place. This segment is located west of the Azores
between 36858 and 36834
0 N at latitude 33816
0 W. The segment has a total
spreading rate of about 1.2 cm per year. The Franco-American Mid-Ocean
Undersea Survey project (FAMOUS) was designed to make detailed observations
on a diverging plate boundary where new crust was being created on a ridge
segment influenced by the Azores hotspot.
The Mid-Atlantic Ridge
171