Geoscience Reference
In-Depth Information
(a)
ANOMALY M22
ANOMALY M12
ANOMALY 34
ANOMALY M0
Figure 3.21.
(a) Reconstructions of the positions of South America, Africa and
Antarctica at the time of anomalies M22, M12, M0 and 34. (From Lawver
et al.
(1985).)
before, as anomaly information is not available for the Magnetic Quiet Zone), the
Southeast Indian Ridge started spreading. This began the splitting of Australia
from Antarctica. At the same time, India began to move rapidly northwards from
Antarctica. The Carlsberg-Central Indian Ridge also started spreading, sepa-
rating Africa from India. The half-spreading rate of the portion of the South-
east Indian Ridge between Australia and Antarctica was slow (perhaps only
0.5 cm yr
−
1
), whereas the spacing of the same anomalies to the south and east of
India indicates half-spreading rates of 10 cm yr
−
1
or more for the ridge between
India and Antarctica (Fig. 3.21(b)). Figure 3.21(c) illustrates the relationship
between the Reunion hotspot and the Deccan Traps, a very major flood-basalt
