Discussion

Arrange the sentences A, B, C, and D from a logical sequence between sentences 1 and 6.

1. The idea of sea-floor spreading actually preceded the theory of plate tectonics.
A. The hypothesis was soon substantiated by the discovery that periodic reversals of the earth’s magnetic field are recorded in the oceanic crust.
B. In its original version, it described the creation and destruction of ocean floor, but it did not specify rigid lithospheric plates.
C. An explanation of this process devised by F.J. Vine and D.H. Mathews of Princeton is now generally accepted.
D. The sea-floor spreading hypothesis was formulated chiefly by Harry H. Hess of Princeton University in the early 1960’s.
6. As magma rises under the mid-ocean, ferromagnetic minerals in the magma become magnetised in the direction of the geomagnetic field.