| Popis: |
It is well known that a general relationship exists between the age of the earth's crust at mid-ocean ridges and its depth (Menard, 1969; Sclater and Francheteau, 1970; Sclater et al., 1971). Depths increase from 2500 300 meters at a spreading center, to 5800 5300 meters in oceanic crust of Early Cretaceous to Late Jurassic age (Figure 1; Sclater et al., 1971). The 3 km deepening of the oceanic crust can be satisfactorily explained by simple models involving the thermal structure of the oceanic lithosphere during its spreading from the axis of ridges to the adjacent oceanic basins (Sclater and Francheteau, 1970; Davis and Lister, 1974). It has also been suggested that structural highs like aseismic ridges, which have not come about by accretion, nevertheless follow the subsidence law of normal oceanic crust since they ride "piggy-back" on top of the oceanic lithosphere immediately after their creation at or close to spreading centers (Detrick et al., 1977). [NOT CONTROLLED OCR] |
