Greinar (Vísindafélag Íslendinga) - 01.01.1977, Page 61

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Fig. 8. Schematic picture of pressure ridges formed by storm in Arctic sea-
ice. Illustration of accumulation of wind stress.
much lower than we assumed, when the duration of the storm
is taken into account. So x, will in reality be much below 1500
km. The ridge formed will be essentially floating, as we indi-
cate by a root. If there is some strength in the first ridge, the
next one can be formed a short distance downwind, which
gives a realistic picture of many areas of pressure ridges in
the Central Arctic.
The essential point in this example is, that the floating ice
is capable of conveying and, at the same time, summarizing
the wind stress. That is possible in this case, because floating
on water allows such strain in the ice, i.e. shortening of each
ice element along the x-axis, which corresponds to the increas-
ing compressive stress.
Is there anything in the earth’s crust which corresponds to
the water in this respect? Yes, there seems to be no doubt about
that, at least in the regime of the submarine oceanic ridges,
and in the volcanic zones in Iceland. And on the basis of the
Pleistocene worldwide explosive volcanism, it must be of wider
occurrence.
This effect we derive from the shallowness of earthquakes.
Earthquakes prove that the earth’s upper layers are perpetually
under non-hydrostatic stresses, and strain energy is constantly
being pumped into these upper layers, to compensate for the
strain energy lost in earthquakes.