Geoscience Reference
In-Depth Information
Table 9.2
Layering of the oceanic crust beneath the ocean basins
Range of seismic
velocity (km s
−1
)
Layer
Thickness (km)
Sea water
4.5
1.5
Layer 1 (sediment, variable)
About 0.5
About 2
Layer 2 (volcanic layer)
2.11
±
0.55
2.5-6.6
Layer 3 (oceanic layer)
4.97
±
0.90
6.6-7.6
Layer 4 (upper mantle)
7.9-8.1
Total igneous crust
7.08
±
0.78
Note
: This layering is the mean seismic structure of 'normal' oceanic crust.
Source
: After White
et al
.(1992).
Figure 9.3.
Drilling into
the oceanic crust. Finding
the hole for re-entry, a
long way down.
Development of deep
drilling techniques led to
much improved
knowledge of the oceanic
crust and palaeoclimate.
(From Wyllie (1976).)
mature oceanic crust beneath the ocean basins as determined from first-P-wave-
arrival travel times. However, subsequent improvements in the techniques for the
inversion of seismic wide-angle reflection and refraction data (including compu-
tation of synthetic seismograms; see Section 4.3)have provided a much improved
resolution of seismic structure of the oceanic crust. The original four layers of
